Diet is one the most common cause of calcium oxalate stones. High dietary calcium intake or secondary causes can lead to hypercalciuria which promotes the precipitation of calcium deposits (Pak et al., 2011). These deposits, along with other risk factors such as an alkaline urinary pH, hyperoxaluria, hypocitraturia, and anatomical abnormalities, contribute to the formation of calcium oxalate stones. Secondary causes can further exacerbate hypercalciuria, including increased gastrointestinal calcium absorption, increased bone turnover, or decreased renal tubular reabsorption (Worcester and Coe, 2008). Dietary protein also plays a significant role in stone formation. Increased dietary protein intake raises acids production in the body, which can stimulate bone resorption and result in higher calcium excretion (Goldfarb, 1988). The acidic excretion of uric acid further impairs calcium reabsorption, contributing to hypercalciuria and stone formation. Additionally, the protein-induced hypercalciuric effect may increase urinary sulfate excretion which form calcium-sulfate complexes in renal tubules. These poorly absorbable complexes can perpetuate nephrolithiasis by further promoting stone formation (Goldfarb, 1988; Minisola et al., 2018).

Hypercalciuria is often driven by hypercalcemia, which is tightly regulated by parathyroid hormone, and calcitriol. These regulatory mechanisms work together to maintain stable blood calcium levels. However, hormonal abnormalities can disrupt this balance, causing the renal system to improperly reabsorb calcium and instead secrete it excessively, leading to hypercalciuria (Pak et al., 2011; Minisola et al., 2018). In addition to dietary factors, hormonal imbalances contribute to calcium oxalate stone formation, with the most common causes being hyperparathyroidism. This can manifest as primary hyperparathyroidism caused by overactive parathyroid glands excessively producing parathyroid hormone (PTH), or secondary hyperparathyroidism where an exogenous factor such as CKD or vitamin D deficiency stimulates increased PTH production. PTH plays a central role in calcium homeostasis by promoting hypercalcemia. It does it by increasing the synthesis of calcitriol, which enhances intestinal absorption of calcium; and by regulating the renal system to increase calcium reabsorption. Additionally, PTH accelerates bone turnover, releasing calcium into the bloodstream (Coe et al., 1992). These mechanisms collectively elevate both blood and urine calcium concentrations, significantly increasing the risk for calcium-related kidney stones in a state of hyperparathyroidism.

The physical process of calcium oxalate stone formation begins with urinary supersaturation and the retention of crystals in kidney pouches. It is theorized that ulceration at the papillary surface creates a stone nidus, which promotes renal tubular injury and facilitates crystal nucleation (Tsujihata, 2008). This interaction between crystals and cells forms the foundation for stone growth (Tsujihata, 2008). A key side in this process is the formation of Randall’s plaques, subepithelial calcium phosphate deposits that develop under supersaturated conditions (Figure 1). These plaques become embedded in the urothelium, initiating crystal formation (Tsujihata, 2008; Mulay et al., 2013). Once the crystals adhere to renal tubules or papilla, their surface are exposed to further nucleation (Tsujihata, 2008; Leslie et al., 2025). This spontaneous process depends on urinary composition, flow, and pH; then crystal aggregation occurs when calcium oxalate crystals cluster together, driving stone growth (Tsujihata, 2008; Mulay et al., 2013; Leslie et al., 2025). Current research is investigating the role of urothelial cell surface injury and repair. Alterations in cell surface molecular expression might contribute to recurrent stone formation by creating favorable conditions for crystal adhesion and retention (Asselman et al., 2005).

Many factors promote the assembly and activation of NLRP3, as seen in nephrolithiasis and its association with CKD. While nephrolithiasis is known to cause renal inflammation and damage, the specific mechanisms underlying its action remain widely debated. Activation of the NLRP3 inflammasome follows a two-step mechanism: priming and activation. In renal tubular epithelial cells, priming involves upregulation of NLRP3 expression and is triggered by calcium oxalate crystals adhering to or penetrating the plasma membrane (Sun et al., 2015; Sun et al., 2017). This interaction leads to the release of danger-associated molecular patterns (DAMPs), such as ATP (Rumora et al., 2021), which initiate signaling pathways, such as NF-κB, that increase transcription of inflammasome components (Liu et al., 2017).

The second step, activation, involves the assembly and functional triggering of the inflammasome complex. In epithelial cells, this step is typically induced by increased potassium efflux (i.e., a decrease in intracellular K⁺ concentration) through ion channels. Potassium efflux is a well-established trigger of NLRP3 inflammasome activation, whereas the role of calcium flux in this process remains controversial (Huang et al., 2023). Mulay et al. used mouse models to investigate calcium oxalate crystal-induced NLRP3 activation. They proposed that phagocytosis of calcium oxalate crystals, interconnected with potassium efflux, results in NLRP3 activation. To test this, they used Cytochalasin D, an inhibitor of actin polymerization that blocks phagocytosis, which reduced crystal uptake and decreased IL-1β secretion. Furthermore, blocking potassium efflux via high extracellular potassium produced the same outcome, preventing inflammasome activation, an effect similarly observed in monocytes and bone marrow–derived macrophages (Mulay et al., 2013; Munoz-Planillo et al., 2013; Gritsenko et al., 2020). However, cytochalasin D has also been shown to impair potassium efflux directly, suggesting that it may affect both phagocytosis and ion flux (Munoz-Planillo et al., 2013). These findings demonstrate a direct molecular mechanism in which calcium oxalate phagocytosis induces NLRP3 activation, leading to IL-1β production and subsequent renal inflammation. Expanding their investigation, Mulay et al. examined diffuse crystal deposition in calcium oxalate treated mice and its association with renal failure. They observed that mice with calcium oxalate deposition exhibited increased diffuse neutrophil infiltrates and tubular necrosis, characterized by granular casts and transient elevations in plasma creatinine and blood urea nitrogen (BUN) levels (Mulay et al., 2013). This research highlights the acute inflammatory role of NLRP3 activation by calcium oxalate stones, emphasizing its contribution to renal damage and inflammation.

CP-456,773 has emerged as a promising NLRP3 inflammasome inhibitor. In mouse models, CP-456,773 has been shown to suppress IL-1β and IL-18 levels demonstrating efficacy comparable to genetically NLRP3-deficient mice (Joshi et al., 2015; Primiano et al., 2016). Studies comparing wild-type (WT) mice to mice on an adenine-enriched diet (which promotes calcium oxalate stone formation) revealed that CP-456,773 treatment significantly lowered serum levels of BUN, creatinine, indicating reduced renal injury. However, it did not prevent crystal formation as both treated and untreated mice exhibited intrarenal crystal deposits (Joshi et al., 2015; Primiano et al., 2016).

Although CP-456,773 does not directly prevent kidney stone formation, it plays a crucial role in reducing renal inflammation, mitigating fibrosis, and preventing further tubular damage. By interrupting the inflammatory cycle driven by NLRP3 activation, CP-456,773 could indirectly slow nephrolithiasis progression, making it a valuable therapeutic candidate for inflammation-associated kidney stone disease.

Among pharmacological agents with anti-inflammatory properties, atorvastatin has shown therapeutic potential in calcium oxalate stone formers. While primarily known as a HMG-CoA reductase competitive inhibitor, atorvastatin also functions as an indirect inhibitor of the NLRP3 inflammasome, primarily by reducing oxidative stress and crystal deposition (Tsujihata, 2008; Joshi et al., 2015). Since CaOx crystals activate NLRP3 inflammasome via ROS/TXNIP pathway, atorvastatin helps mitigate oxidative stress, thereby reducing inflammation and preventing further stone aggregation (Tsujihata, 2008; Joshi et al., 2015). Beyond its role in lowering renal inflammation, atorvastatin is also used to reduce serum triglycerides and increase HDL levels, making it an effective treatment for hypercholesteremia, a condition that can secondarily contribute to nephrolithiasis. By addressing dyslipidemia, atorvastatin not only prevents further renal damage, but may also reduce the risk of recurrent kidney stone formation.

Another pharmacological agent of potential interest is phenylbutyric acid. Although it is an endoplasmic reticulum (ER) stress inhibitor and has not been directly implicated in the inhibition of NLRP3, phenylbutyric acid has been shown to reduce CaOx deposition and improve mitochondrial function in renal tubular epithelial cells. Additionally, it mitigates mitochondria-induced inflammation and ROS damage (Sharma et al., 2019). While its precise mechanism of action remains unclear, proposed models suggest that ER stress disrupts calcium homeostasis by altering calcium ion uptake and release. This imbalance leads to excessive calcium influx into the mitochondria, which in turn triggers ROS generation and disrupts the function of complex I/III and cytochrome c in the electron transport chain, ultimately impairing mitochondrial function. Mitochondrial dysfunction plays a key role in the activation of the NLRP3 inflammasome, a process that is further regulated by P2X7 receptor signaling (Figure 1).

Blocking P2X7 receptor activation, using ROS scavengers, is also an interesting pharmacological target. The P2X7 receptor is a ligand-gated ion channel activated by extracellular ATP, which is often released during cell stress, damage, or inflammation (Pelegrin, 2021). Its activation triggers NLRP3 inflammasome signaling through two primary pathways. First, activation of the P2X7 receptor leads to a sustained increase in intracellular calcium levels (Figure 1) by promoting calcium influx from the extracellular space and stimulating the release of calcium from the ER. This calcium overload damages mitochondria, causing the release of mtDNA, a known activator of the NLRP3 inflammasome (Gurcel et al., 2006). Second, P2X7 receptor activation reduces intracellular cAMP levels, which weakens cAMP-mediated inhibition of NLRP3 inflammasome activation. This process results in an increased abundance of the NLRP3 inflammasome, further driving inflammation and tissue damage (Rajamaki et al., 2013). Beyond its role in mitochondrial metabolism, mitochondria also regulate inflammatory cytokine expression through post-translational modifications and activation mechanisms. Persistent mitochondrial stress and ROS overproduction promote NLRP3 inflammasome assembly, leading to the secretion of pro-inflammatory cytokines IL-1β and IL-18. These cytokines exacerbate renal inflammation, ultimately contributing to tubular damage, fibrosis, and kidney stone formation (Figure 1). Given the interplay between mitochondrial dysfunction, ER stress, and P2X7 receptor signaling, targeting these pathways, through inhibitors like atorvastatin and phenylbutyric acid, may offer a therapeutic strategy to reduce inflammation and prevent kidney stone progression.

NLRP3 plays a critical role in both nephrolithiasis and CKD. Targeted inhibition may help reduce inflammation, prevent stone recurrence, and preserve kidney function. Continued research is essential to bring these therapies into clinical practice and improve patient outcomes. Future studies should evaluate the efficacy of direct NLRP3 inhibitors in kidney stone patients, as well as the long-term effects of indirect agents. Combination therapies, such as pairing NLRP3 inhibitors with antioxidants, or ER stress blockers, may offer synergistic benefits. Longitudinal research should also investigate whether targeting NLRP3 can slow CKD progression, particularly in high-risk populations.