By preventing the development of acquired immunodeficiency syndrome (AIDs), highly active antiretroviral therapy (HAART) has changed the landscape of illness for patients infected with human immunodeficiency virus (HIV) from a universally fatal diagnosis into a manageable chronic illness. As patients with HIV are living longer, other aspects of HIV infection have come into the forefront. For instance, even patients with good viral load and a relatively healthy immune system often suffer from a high rate of HIV-associated cardiomyopathy (HIVAC) (Pinto and da Silva, 2018; Feinstein, 2023; Freiberg, 2023). Prior to the widespread use of HAART, a high proportion of patients with AIDS had cardiac abnormalities (Pinto and da Silva, 2018; Sinha and Feinstein, 2020) and AIDs patients with cardiac abnormalities had a 5.86 hazard ratio for death in comparison to patients with idiopathic cardiomyopathy (Felker et al., 2000). Despite HAART, the prognosis for HIV infected patients with cardiomyopathy remains similarly grim (Freiberg, 2023). A meta-analysis assessing cardiac function in 2,242 asymptomatic patients with well controlled HIV-1 demonstrated systolic dysfunction in 8.3% of patients and diastolic dysfunction in 43.4% (Cerrato et al., 2013). HIVAC disease now accounts for a quarter of deaths in patients with HIV and is associated with 4.0 and 6.5 times higher risk for death, in asymptomatic and symptomatic patients, respectively (Crum et al., 2006). Reduced myocardial systolic function in HIVAC patients was correlated with high lipid and fibrosis indexes in the myocardial tissue (Thiara et al., 2015). This holds true in non-human primate models as Rhesus macaque monkeys infected with HIV-like simian immunodeficiency virus (SIV) showed HIVAC-like dilated cardiomyopathy and fibrosis correlating with elevated numbers of myocardial CD163+ macrophages (Shannon et al., 2000; Walker et al., 2014). Despite the clinically well-characterized nature of HIVAC, prognosis for these patients remains poor due to a lack of treatments directly targeting the mechanisms behind HIVAC development (Ntsekhe and Baker, 2023).

The drivers behind HIVAC development is assumed to be multifactorial. Factors believed to contribute to the development of HIVAC include heightened cytokines expression, co-infection with bacteria or viruses known to affect the myocardium, HIV induced autoimmunity, and, most recently, direct infection of the myocardium by the HIV virus (Anand et al., 2008; Otis et al., 2008; Sillman et al., 2008; Meng et al., 2013; Sinha and Feinstein, 2020; Perkins et al., 2023). Here we discuss research suggesting HIV infection induced dysregulation of myocardial autophagy a mechanism for HIVAC development. These studies present autophagy modulators as potential pharmaceutical targets for normalizing autophagy function and improving cardiac function in HIV patients.

HIV-related cardiomyopathy involves multiple structures in the heart, including the coronaries, pericardium, endocardium, myocardium, and valvular structures as well as indirect involvement on preload and afterload through pulmonary and systemic vasculature (Manga et al., 2017; So-Armah et al., 2020). In a large population study of patients who died from acquired immunodeficiency syndrome AIDS, cardiac disease was documented in 18.6% (82 of 440) of patients and an additional 2.7% (12/440) who suffered from dilated cardiomyopathy and 6.8% who suffered from (30/440) lymphocytic interstitial myocarditis. Of the 82 patients with cardiac disease, 33.3% (28/84) had infective endocarditis, 63.1% (53/84) had pericardial effusion, and 1.2% of patients (3/84) had myocardial sarcoma and lymphoma (Barbaro et al., 1998). Of the 29 patients with active infective endocarditis, in situ hybridization with HIV specific probes showed active HIV myocarditis in 25 of these patients (Barbaro et al., 1998).

A 2017 study reported HIV infection of cardiac endothelial cells leads to an interleukin-1/-6 and tumor necrosis factor-alpha stimulated release of pro-inflammatory cytokines that ultimately resulted in chronic endovascular inflammation and subsequent life-threatening endocarditis and cardiac dysfunction (Monsuez et al., 2007; Duprez et al., 2012; Manga et al., 2017). Structurally speaking, an echocardiographic study on 803 HIV-positive patients found 77% of patients to have valvular dysfunction (Reinsch et al., 2013; Hu et al., 2023). In animal models, CCR5 and CXCR4 receptor independent HIV cardiomyocyte infection has been demonstrated to have a profound impact on cardiomyocyte function. Scanning electron microscopy showed invasion through this process as mediated by NRVM gp120 and adjacent perivascular CD68-positive macrophages (alkaline phosphatase-BCIP) resulted in cardiomyocyte damage and subsequently caused cardiac dysfunction in neonatal rat ventricular myocytes (NRVM) (Fiala et al., 2004; Fiala et al., 2004; Herskovitz and Gendelman, 2019; Lodge et al., 2020).

Despite the clear involvement of HIV in all three layers of the heart, the exact location through which HIV viral particles initiate cardiac invasion remains unclear. There are three avenues through which cardiac HIV infection could occur: coronary invasion, endothelial invasion via cardiac chambers, and pericardial invasion. HIV in systemic circulation eventually reach the coronary arteries through which viral particles can infect the endothelium, intima, media, and adventitia and eventually the myocardium. HIV viral particles in circulation also come into direct contact with the cardiac chamber endothelium, leading to lethal inflammation endocarditis prior to infection of the cardiomyocytes (Figures 1A, B). While traveling along the bloodstream, HIV particles are transported into heart and can directly infect endothelial cells and/or cardiomyocytes through the above three pathways. These viral particles anchor onto cell membranes via interaction of HIV GP-120 to cytoplasmic integrated protein CD4 and CCR5. Viral genomic RNA is then injected into the cells and proceed to hijack host genomic DNA with HIV reverse transcriptase (Figures 1C, D), which begins the production process of millions more particles. Lastly, pericardial distribution of HIV can lead to significant inflammation and pericardial effusion over the visceral layer of the epicardium (Wang et al., 2020).

HIV can cause a variety of cardiac disease via one or more of above three possible paths of entry. In the following review, we focus on the mechanistic role autophagy plays in HIV infection regardless of avenue of entry into cardiomyocytes and discuss possible pharmaceutical targets against autophagy dysregulation in HIVAC and HAART therapy.

Autophagy is a cellular process integral to normal cellular regulation, recycling, and decomposition of old, unnecessary, damaged or dysfunctional intracellular components as well as external pathogens. This natural process undergoes four phases—cytoplasmic autophagosome formation, fusion of autophagosome and lysosome, degradation of dysfunctional component, and utilization of repurposed amino acids [Refer to Reviews: Bagherniya et al., 2018; Kaur and Debnath, 2015; Miyamoto 2019]. More than 50 different autophagy-related (ATG) proteins are involved in the autophagy pathway, and ATG dysfunction is critical to the development many diseases including cancer, neuronal disorders, liver disease, diabetes, and heart diseases [Refer to Reviews: Klionsky et al., 2021; Levine and Kroemer, 2019; Ramesh et al., 2019]. However, the link between autophagy and HIV associated heart disease has yet to be explored. In this review, we focus on the role of autophagy dysregulation in HIV associated cardiac pathology and explore how recent characterization of autophagy can potentially be harnessed to provide treatments benefiting HIV patients.

Autophagy has been shown to play a critical a role in HIV-1 related complications. As a function vital to normal cellular catabolism, autophagy is not only vital for eliminating cellular waste, intracellular pathogens, and damaged organelles, but also needed for cellular synthesis and maintaining energy for cell renewal. Together these functions act as an intracellular recycling system that facilitate dynamic circulation of catabolized building blocks, thereby promoting biosynthesis, boosting ATP production, and maintaining nutrient homeostasis (Mizushima and Komatsu, 2011; Chiramel et al., 2013; Kaur and Debnath, 2015; Ramesh et al., 2019; Chen et al., 2023). Several recent in vitro and in vivo investigations have unveiled the fundamental role of autophagy in system specific manifestations of HIV. For example, a significant increase of autophagy markers Beclin1, autophagy-specific gene 5 (Atg-5), Atg-7, and LC3-II were observed in the brain tissue of HIV-1 encephalitis patients. This suggests autophagy dysregulation may play an important role in the pathogenesis of other devastating neurological complications of AIDS (Levine and Sodora, 2006; Mizushima, 2020; Judith and Berlioz-Torrent, 2023).

As a cellular function long considered a major regulator in cardiac homeostasis and function, autophagy is a key suspect in HIVAC. Autophagy loss-of-function models with constitutional deletion of atg5 and beclin 1 (Nakai et al., 2007) develop severe cardiac pathology. Similarly, cardiac-specific deletion of autophagy gene forkhead box O1 (FoxO1) (Hariharan et al., 2010; Popov et al., 2023) also develop severe cardiac defects. Cardiac dysfunction in both models is due to accumulation of misfolded proteins and dysfunctional organelles caused by autophagy dysfunction. Protein-aggregation mouse models generated by activating major suppressors of autophagy, such as mammalian Ste20-like kinase 1 (Mst1) and mammalian target of rapamycin (mTOR), also exhibit severe cardiac disorder.

Importantly, removing accumulated misfolded proteins by re-activating the autophagy pathway can recover dysfunctional mitochondria and repair damaged DNA, which in turn, rescue cardiac function (Maejima et al., 2013; Sciarretta et al., 2018a; Sciarretta et al., 2018b; Gatica et al., 2022). Studies have also shown autophagy activation to inhibit chronic ischemic remodeling and mediate cardiac adaptation to overload stress by reducing the accumulation of misfolded proteins such as amyloid, pre-amyloid oligomers, and poly-ubiquitin proteins (McLendon and Robbins, 2015; Gupta et al., 2017; Levine and Kroemer, 2019). Autophagy is now considered a cellular process vital to healthy cardiomyocyte aging, protein quality control, and pathogenesis (Levine and Kroemer, 2008; Wang et al., 2008; Shirakabe et al., 2016; Sciarretta et al., 2018b; Klionsky et al., 2021). As increasing evidence mounts of HIV directly disrupting its regulators and proteins, autophagy is under investigation as a key component in HIVAC pathogenesis.

HIV-1 infection has recently been shown both in animal models and patients to affect basal cardiomyocyte autophagy flux. HIV-1 infected cardiomyocytes express significantly higher levels of type I and II microtubule-associated protein-1 β light chain (LC3), which has been shown to inhibit autophagy in cardiomyocytes after long-term culture. Subsequent cells cultured within media collected from of HIV-1-infected cardiomyocyte cultures also resulted in the accumulation of LC3-II, ubiquitin, and SQSTM1/p62 labeled pre-maturation and degradation autophagosomes (Gupta et al., 2017; Zhao et al., 2021). This accumulation of autophagosomes within HIV-1 infected cardiomyocytes in addition to the classic mechanisms of HIV infection: hijacked reverse transcription, integration of viral RNA into host genomic DNA, and subsequent change in cellular activity, likely all contribute to the development of HIVAC (Figure 2). In addition to the inherent damage caused by the loss of conserved cellular catabolism, dysfunctional autophagy also contributes to myocardial superinfection susceptibility (Ramesh et al., 2019). Here we summarize the molecular mechanisms through which HIV-1 negative regulatory factor (Nef), glycoprotein 120 (gp120), and transactivator (Tat) interact with proteins vital to phases of the autophagy cycle and analyze their roles in HIVAC disease progression (Figure 3).

The multifunctional viral accessory protein Nef plays a role in viral replication, assembly, budding, infection, and immune evasion—all vital to the life span of the virus (Mailler et al., 2019). This 27–32 KDa protein is expressed from early on in the infection process and is key in many aspects of viral infection and CD4⁺ T-cell suppression. Nef downregulates CD4 and major histocompatibility complex-I (MHC-I) expression in infected cells, thereby allowing infected cells to avoid detection by cytotoxic T-cells. HIV Nef secreted in exomes are also thought to trigger CD4⁺ T cell apoptosis, thereby contributing to the hallmark CD4 lymphopenia seen in AIDS (Lenassi et al., 2010; Caucheteux et al., 2023). HIV-1 Nef is also known preserve newly produced infectious viruses by constraining autophagosome maturation and acidification (Chiramel et al., 2013; Zhao et al., 2021; Kyei et al., 2009). Nef inhibits autophagosome maturation by increasing the expression of LC3-II and interacting with Beclin-1 to reduce autophagic degradation of the viral capsid protein p24. In addition to these key infective and immunosuppressive activities, recent studies have shown Nef to pay a role in HIVAC through interruption of autophagy. Guptal et al. reported cardiac specific expression of Nef to inhibit cardiomyocyte autophagy, leading to an accumulation of dysfunctional protein that interfered with myocardial contractile function and ultimately led to significant in vitro cardiomyocyte toxicity and death. They showed that HIV Nef accumulating in exosomes mature into autophagosomes by interacting with viral maturation factors, Beclin-1 and Rab7, subsequently causing substantial storage of poly-ubiquitin and p62 proteins in HIV-1 infected cardiomyocytes (Gupta et al., 2017; Cheney et al., 2020). Removal of functional poly-ubiquitin and p62 proteins then halt autophagosome at the maturation stage, leading to an accumulation of dysfunctional autophagosomes in cardiomyocytes (Figure 3). Interestingly, even during adequate HAART therapy, viral Nef has been found to accumulate in HIV and SIV infected cardiomyocytes, which may explain why HIVAC is prevalent even when the infection is considered clinically well-controlled with normal CD4 counts and low viral load.

As a key protein on the surface of HIV, gp120 mediates invasion of HIV and SIV viruses into host cells. During the initial infection, viral gp120 first binds to CD4 on the host-cell surface, leading to a change in its spatial conformation which in turn mediates the interaction of viral glycoprotein 41 (gp41) with host C-C Chemokine Receptor type 5 (CCR5) (Xu, 2020). This process triggers the fusion of cellular and viral membranes, releasing viral RNA into the host cytoplasm (Saayman et al., 2015). In addition to this key function, HIV-1 gp120 has been shown to induce autophagy in neurons and T lymphocytes. This phenomenon has since also been identified in vitro H9c2 cardiomyocytes. Recent in vitro studies have further traced this affect to HIV-1 gp120 induced expression of ATG7, Beclin 1, LAMP1 and LC3-II—autophagy related proteins found in cardiomyocytes (Meng et al., 2013). This study also found interaction between gp120 and N-methyl-D-aspartate receptor (NMDA) to be a requirement for gp120 induced autophagy in H9c2 rat cardiomyocyte cells and can be significantly inhibited with NMDA receptor inhibitors (Meng et al., 2013). Gp120 was further proven to act through the autophagy pathway as inhibitors of autophagy regulators, c-Jun N-terminal kinase (JNK) and phosphoinositide 3-kinase (PI3K), rescue gp120-induced autophagy hyper-activation in H9c2 rat cardiomyocytes. Other in vivo work has since verified the direct inhibitory action of JNK inhibitor (SP600125) and class III PI3K inhibitor (3-MA) on the expression of autophagy regulators ATG7, Beclin one and LAMP1. Importantly, these inhibitors reduced cellular autophagy and improved structure and function of HIV-infected cardiomyocytes (Meng et al., 2013).

HIV Tat is necessary for integration of viral genomic RNA into host genomic DNA for viral replication and expression (Debaisieux et al., 2012; Jiang et al., 2018). In addition to this already pivotal role, recent research has suggested Tat also plays a vital role in the development of dilated cardiomyopathy in HIV infected individuals. Transgenic mice engineered to express HIV-1 Tat developed reduced percentage of fractional shortening in isolated cardiomyocytes. Physiologically, this resulted in depressed peak left ventricular systolic pressure (LVSP) and elevated left ventricular end-diastolic pressure (LVEDP) consistent with decreased systolic and diastolic function intermediated through cardiac Ryanodine Receptor associated Calcium homeostasis (Raidel et al., 2002; Fang et al., 2009; Alomar et al., 2022). The specific mechanism through which Tat acts on cardiomyocyte autophagy has been traced to autophagy related proteins LC3-II and p62. Tahrir et al. confirmed the ability of HIV-1 Tat to decrease the expression of LC3-II and p62 in cardiomyocytes. This disrupts the formation and maturation of autophagosomes, resulting in cardiomyocytes with an accumulation of misfolded proteins and damaged organelles. This in combination with Tat’s ability to induce oxidative stress in cardiomyocytes significantly impacts cardiomyocyte health and homeostasis (Tahrir et al., 2018).

HIV Tat’s ability to alter cellular homeostasis also occurs in HIV-associated neurodegenerative disease (HAND) (Fields et al., 2015; Mehrbod et al., 2019; Ramesh et al., 2019; Marino et al., 2020). Treatment of B103 neuronal cells and primary mouse neurons with increasing concentrations of recombinant HIV-1 Tat produces dose-dependent inhibition of LC3-II and ubiquitin-binding sequestosome 1 (SQSTM1/p62) protein expression. Furthermore, in immunoprecipitation and double-immunolabeling experiments, HIV Tat was co-localized with lysosomal-associated membrane protein 2A (LAMP2A) in the cytoplasm. This co-localization inhibited autophagosome-lysosome fusion in neurons and caused an accumulation of misfolded proteins and damaged organelles similar to that seen in HIV-1 infected cardiomyocytes (Fields et al., 2015). In vivo models of HAND confirmed the physiologic effect of these findings, when neurons from glial fibrillary acidic protein- Tat (GFAP-Tat) mice showed altered LC3-II levels and increased autophagosome accumulation correlating with neurodegeneration. Notably, these effects were reversed by treatment with rapamycin, an autophagy activating mTOR inhibitor (Fields et al., 2015). HIV Tat expression has also been shown to induce dose-dependent higher levels of BCL associated athanogene 3 (BAG3) induced autophagy in glioblastoma cell lines (Bruno et al., 2014). Interestingly, BAG3 is known to interact with molecular chaperone heat shock protein 70 (HSP70) to modulate cellular autophagy in the heart (Inomata et al., 2018). Recent work in C57BL/6J mice has also linked SQSTM1/p62 expression, which is downregulated in HANDs, with cardio-protectively during stress-generating short-term exercise (Feng et al., 2019; Yamada et al., 2019; Ning et al., 2023). Other rat models have also shown the SQSTM1/p62 associated Nrf2 signaling pathway to play a critical role in autophagy-dependent cardiac protection against myocardial ischemia and age-related cardiac dysfunction (Bhide et al., 2018; Ning et al., 2023). Given these known functions of QSTM1/p62 and Nrf2 in cardiomyocytes and the pathogenic role these same proteins play in HIV-associated neurodegenerative disease, the same proteins likely play a similar role in HIV-associated cardiac disease.

Given the essential role mTOR plays in vital cellular functions, this pathway and its substrates have been studied across many cell types. Many of these studies have found pharmacologic inhibition of this pathway to be beneficial for a variety of pathogenic processes. A common thread across these studies is that mTOR inhibition promotes autophagy to promote clearing of misfolded or dysfunctional proteins, organelles, and other cellular components (Nair and Ren, 2012; Kumar et al., 2020; Liu and Sabatini, 2020; Taylor et al., 2020). For instance, mTOR inhibitor rapamycin reduced renal podocyte injury and improved the glomerular filtration barrier in rat models for renal injury by increasing autophagy levels in the podocytes of treated animals (Wu et al., 2013). Rapamycin also promoted cell death in human neruoblastoma cell lines by arresting them at the G0/G1 phase of the cell cycle. Evaluation of these rapamycin treated, arrested cells showed increased number of autophagosomes and elevated expression of autophagosome proteins Beclin-1 and LC3-II/LC3-I (Lin et al., 2018). Rapamycin induced autophagy is also theorized to provide a protective effect in human neurodegenerative disorders, such as Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease by clearing the key disease feature: aggregate proteins (Rahman and Rhim, 2017; Mputhia et al., 2019; van Montfort et al., 2019).

Rapamycin has provided beneficial effects in a range of animal models for cardiovascular disease including rat models of tetrachloride carbon (CCl4) induced cirrhotic cardiomyopathy (Saeedi Saravi et al., 2016), rat models of uremic cardiomyopathy (Haller et al., 2016), mouse models of genetic hypertrophic cardiomyopathy (Xu et al., 2014), and mouse models of metabolically driven CVD (Reifsnyder et al., 2018; Singh et al., 2022). Across all of these models, an increase in autophagy was observed followed by an improvement in myocyte contractility or cardiac function. Rapamycin was also reported to provide a cardio-protective effect in an animal model for myocardial ischemia reperfusion injury (Khan et al., 2006). In the reperfusion injury study, rapamycin treated mice had 64% decreased area of necrosis and apoptosis in comparison to the untreated group (Khan et al., 2006; Shimada et al., 2021; Xie et al., 2021). Rapamycin also prevented cardiac dysfunction in models of chronic disease. Treatment with rapamycin restored fractional shortening and ejection fraction in mouse models of diabetes mellitus (T2D) by blocking enhanced phosphorylation of mTOR, reducing oxidative stress, and normalizing glucose metabolism regulators (Das et al., 2014). While these studies modeled disease with very different pathogeneses, treatment with rapamycin altered autophagy or mitophagy to improve cardiac function across all models.

As a cardiac disease with underlying pathologies in mitochondrial regulation and reduced autophagy, HIV-associated cardiomyopathy is expected to respond to mTOR inhibitor normalization of mitophagy and autophagy. As previously discussed, rapamycin treatment has been shown to counteract various single components of HIV infection. The mTOR inhibitor increased cellular autophagy in Nef-expressing NRVCs, to normalized cellular apoptotic body formation and facilitate the redistribution and removal of aggregated autophagic proteins LC-II, p62, Beclin1, ubiquitin, and Rab7. This reduced Nef-induced cytotoxicity by allowing cardiomyocytes to normalize autophagy flux. A process that was aided by the simultaneous redistribution of transcription factor EB (TFEB) and cytoplasmic lysosome contents (Gupta et al., 2017). Given the close relationship between mTOR pathway subjects, autophagy, and mitochondrial homeostasis, to the development of HIVAC, a direct inhibition of this aberrant pathway would be an optimal strategy for effective treatment of HIVAC.

As the cellular energy farm, healthy mitochondria is critical to cardiomyocyte function. Normal selective degradation of defective mitochondria through mitophagy is critical to maintaining a healthy mitochondrial population. When mitochondria are damaged fewer ATP are produced to power cardiomyocyte contractility. Damaged mitochondria also generate dangerous amounts of reactive oxygen species (ROS). ROS induced oxidative stress and acidification of the cellular environment causes abnormal post-translational modifications that leads to a catastrophic feedforward cycle of oxidative damage. This environment decreases ATP production by altering the expression of peroxisome proliferator-activated receptors (PPARs), decreasing the activity of tricarboxylic acid cycle (TCA) cycle enzymes, disrupting the electron transport chain (ETC), and further changing oxidative phosphorylation. Alterations of metabolic enzyme activity and ATP production eventually trigger heart failure (HF) as cardiomyocytes lack the ATP necessary to survive (Parihar and Parihar, 2017; Avula et al., 2021; Bulló et al., 2021). Thus, as a regulator of cellular mitochondrial homeostasis, mitophagy is a crucial factor in cardiomyocyte function and cardiac health (Morales et al., 2020; Abdel-Rahman et al., 2021; Ning et al., 2023).

In addition to the role autophagy plays in mitochondria-dysfunction driven HIVAC, autophagy also regulates platelet-derived transforming growth factor beta 1 (TGF-β1) mediated HAART induced CVD (Laurence et al., 2018; Madzime et al., 2021). Like NRTI AZT, which disturbed mitochondrial homeostasis, protease inhibitors (PIs) can also induce ROS overproduction, ubiquitin-proteasome system (UPS) dysregulation, and functional alteration of ion channels in the myocardium (Reyskens and Essop, 2014; Alvi et al., 2018). Although this effect does not appear to act directly on the mitochondria, PIs cause disruption of excitation–contraction coupling, induced calcium overload, and endoplasmic reticulum stress. These changes indirectly alter mitochondrial respiration and impair ATP generation. The PI Ritonavir (RTV) has also been shown to induce an accumulation of ubiquitinated proteins and cause an alteration in lipid metabolism (Reyskens and Essop, 2014; Alvi et al., 2018; Hsue and Waters, 2019). These changes all correlate with a range of clinical presentations of clinical presentations associated with CVD including: ECG abnormalities, lower left ventricular ejection fractions (LVEF), higher pulmonary artery pressure (PASP), dyslipidemia, diabetes, and coronary artery disease (CAD) (Alvi et al., 2018; Hsue and Waters, 2019; Avula et al., 2021).

A recent study by Laurence et al. has found protease inhibitor RTV induced cardiac dysfunction to be dependent upon the expression level of platelet TGF-β1 (Laurence et al., 2017). In a mouse model treated with physiologic levels of RTV, decline in cardiac output, ejection fraction, and stroke volume was correlated with nearly a 5-fold increase of TGF-β1 in myocyte plasma. Interestingly, this TGF-β1 driven RTV-induced cardiac fibrosis can be markedly reduced by treatment with inhaled carbon monoxide (CO). CO upregulates the inducible heme-oxygenase/endogenous CO pathways, thereby modulating both the canonical (Smad2) and non-canonical (p38) pathways of TGF-β1 signaling. Notably, this process was proven to be autophagy dependent as CO treatment provides no protection against RTV-mediated cardiac fibrosis in autophagy-deficient LC3^−/− mice (Laurence et al., 2017). The platelet TGF-β1 dependent pathway for HAART induced CVD is not restricted to PIs. NRTI Abacavir was also found to cause platelet activation and the release of platelet TGF-β1. Identical to PI induced CVD, Abacavir induced activation of platelet TGF-β1 resulted in myocardial fibrosis and subsequent cardiac dysfunction (Satchell et al., 2011; Laurence et al., 2018; Hsue and Waters, 2019).

The convergence of pathogenic mechanisms between both protease inhibitors and nucleoside reverse transcriptase inhibitors presents autophagy as a single, elegantly targetable pathway for the treatment of HAART induced CVD. Given the data discussed above, normalizing autophagy in patients on HAART could recalibrate a range of HAART induced cellular abnormalities. In turn, this improved mitochondrial function, normalized calcium homeostasis, restored ATP production, and stabilized platelet TGF-β1 would prevent the development of HAART induced CVD.

Cardiovascular disease is the number one cause of death in developed nations (Lloyd-Jones et al., 2009). While this collection of diseases is worsened by other factors such as hypertension, dyslipidemia, diabetes, obesity, and smoking, it always accompanies age regardless of lifestyle and risk factors. The key hallmarks of the aging heart are hypertrophy, fibrosis, inflammation and decreased contractility of cardiomyocytes. As a cellular process necessary for clearing away misfolded and dysfunctional proteins, autophagy plays a key role in maintaining cardiomyocyte health and function during the aging progress. Mitophagy, mitochondria specific autophagy, plays an especially important role in the heart as the mitochondria functions to supply ATP for constantly contracting cardiomyocytes and serves as a key regulator in calcium hemostasis. In fact, promoting autophagy has been shown to rescue cardiac disease in some animal models (Khan et al., 2006; Das et al., 2014; Xu et al., 2014; Haller et al., 2016; Saeedi Saravi et al., 2016; Reifsnyder et al., 2018), and has been theorized to decelerate the aging process of the heart (Linton et al., 2015; Shirakabe et al., 2016; Miyamoto, 2019).

Similar to HIV infection, aging has been shown to lead to downregulation of autophagy. Rate of autophagy are thought at to first increase with time as autophagy flux is stimulated by increasing levels of oxidative stress and misfolded proteins within the cell. However, this process can only be maintained for a finite amount duration before the stresses exceed a certain intrinsic threshold, after which cells experience a decline and failure in autophagy. This failure ultimately leads to the inhibition of autophagy in time-worn cells (Shirakabe et al., 2016). A recent study unveiled many transcription factors regulating age-dependent autophagy of the heart such as FoxO, TFEB, hypoxia inducible factor-1 (HIF-1), p53, E2F transcription factor 1 (E2F1), nuclear factor-κB (NF-κB), Kruppel-like factor 4 (KLF4), and zinc finger with KRAB and SCAN domains 3 (ZKSCAN3) (Shirakabe et al., 2016). Many cellular autophagy inhibitors found to be active in aging cells have also been described, including mTOR (Sciarretta et al., 2012; Popov et al., 2023) and Mst1 (Hariharan et al., 2010) or inhibition of main autophagy activators, including sestrin2 (Quanet al., 2017; Zahid et al., 2023; Dai et al., 2023), and sirtuin1 (SIRT1) (Hariharan et al., 2010; Morselli et al., 2010). However, the exact mechanism through which cells regulate autophagy and how cells determine the ageing threshold at which an inhibition of autophagy is preferred over activation requires further investigation.

In young healthy hearts, abnormal mitochondria are rapidly removed by mitophagy. However, as autophagy activity decreases with age, mitophagy also decreases (Sun et al., 2015; García-Prat et al., 2016; Abdellatif et al., 2023; Wang et al., 2023), leading to an abnormal mitochondrial membrane and cellular accumulation of dysfunctional mitochondria in the aging heart (Dutta et al., 2012). Excessive ROS produced by aging mitochondria further adds to cellular stress and damages autophagy activation by modifying autophagy related proteins, such as mTOR, Atg3 and Atg7 (Miyamoto, 2019; Kumar et al., 2020; Mizushima, 2020). Blocking autophagy flux increases cellular mROS, which in turn oxidizes RyR2 in HL-1 cardiomyocytes to stimulate the release of calcium, leading to an electrolyte imbalance that promotes cardiac arrhythmia (Murphy et al., 2019; Avula et al., 2021). The PINK1/Parkin pathway has recently been linked to mitochondrial quality control in the ageing mouse, with the recruitment of Parkin to dysfunctional mitochondria obviously weakened in older cardiomyocytes (Hoshino et al., 2013; Li et al., 2023). Interestingly, overexpression of Parkin in the heart increases mitophagy and provides an anti-aging effect that reduces cellular inflammation and improves cardiac function (Hoshino et al., 2013; Leon and Gustafsson, 2016; Miyamoto, 2019; Abdellatif et al., 2023). These findings add Parkin as another potential therapeutic target for normalizing mitophagy in age, HIV, and HAART related CVD.

Despite HAART greatly reducing the morbidity and mortality of HIV and AIDS, patients on appropriate anti-retroviral therapy still experience a much greater rate of cardiovascular disease than the general population, regardless of CD4⁺ count and viral load. This persistent higher risk for CVD has been linked to autophagy dysregulation, which is known to be a key factor in CVD development of a wide range of etiologies. HIV infection leads to intracellular autophagy imbalance through three key viral components, envelope protein gp120, transcriptional activator Tat, and accessory protein Nef. In addition to playing key roles in the viral infection and reproductive process, all three viral components also significantly alter host cell autophagy flux. Gp120 causes over-activation of early autophagy, while Nef and Tat both restrict the final step of autophagosome maturation, resulting in an accumulation of autophagosomes, and dysfunctional proteins and organelle. Tat adds an extra layer of cellular distress by increasing production of mitochondrial ROS, disrupting the mitochondrial electron transport chain necessary for ATP generation, and altering calcium homeostasis. NRTI azidothymidine and PI ritonavir act through similar pathways, leading to a paralleled accumulation of dysfunctional proteins and mitochondria, and increased mROS that leads to HAART induced myocardial dysfunction and fibrosis. Importantly, mTOR inhibitor rapamycin has been shown to normalize autophagy and restore cardiac function in animal models of autophagy-driven cardiomyopathy. Other effectors of autophagy such as carbon monoxide and inhibitors against autophagy proteins SQSTM1/p62, Beclin1, ubiquitin, Rab7, and the PI3K/mTOR/BRD4 pathway have also shown promising cardio-protective effects. Considering the key role autophagy plays and the positive data showing restoring autophagy can improve cardiac dysfunction, normalizing autophagy pathways should be further studied as a treatment of HIV- and HAART-associated cardiomyopathy.