Cytotoxicity of crystals involves RIPK3-MLKL-mediated necroptosis

Neutrophils and extracellular traps in crystal-associated diseases

Crystalline material can cause a multitude of acute and chronic inflammatory diseases, such as gouty arthritis, silicosis, kidney disease, and atherosclerosis. Crystals of various types are thought to cause similar inflammatory responses, including the release of proinflammatory mediators and formation of neutrophil extracellular traps (NETs), processes that further promote necroinflammation and tissue damage. It has become apparent that the intensity of inflammation and the related mechanisms of NET formation and neutrophil death in crystal-associated diseases can vary depending on the crystal type, amount, and site of deposition. This review details new mechanistic insights into crystal biology, highlights the differential effects of various crystals on neutrophils and extracellular trap (ET) formation, and discusses treatment strategies and potential future approaches for crystal-associated disorders.

Renalase alleviates salt-induced kidney necroptosis and inflammation

Recent evidence suggests that necroptosis may contribute to the development of kidney injury. Renalase is a novel secretory protein that exerts potent prosurvival and anti-inflammatory effects. We hypothesized that renalase could protect the kidney from salt-induced injury by modulating necroptosis. High salt and renalase treatments were administered to Dahl salt-sensitive (SS) rats, renalase knockout (KO) mice, and HK-2 cells. Furthermore, a cohort of 514 eligible participants was utilized to investigate the association between single nucleotide polymorphisms (SNPs) in the genes RIPK1, RIPK3, and MLKL, and the risk of subclinical renal damage (SRD) over 14 years. A high-salt diet significantly increased the expression of key components of necroptosis, namely RIPK1, RIPK3, and MLKL, as well as the release of inflammatory factors in SS rats. Treatment with recombinant renalase reduced both necroptosis and inflammation. In renalase KO mice, salt-induced kidney injury was more severe than in wild-type mice, but supplementation with renalase attenuated the kidney injury. In vitro experiments with HK-2 cells revealed high salt increased necroptosis and inflammation. Renalase exhibited a dose-dependent decrease in salt-induced necroptosis, and this cytoprotective effect was negated by the knockdown of PMCA4b, which is the receptor of renalase. Furthermore, the cohort study showed that SNP rs3736724 in RIPK1 and rs11640974 in MLKL were significantly associated with the risk of SRD over 14 years. Our analysis shows that necroptosis plays a significant role in the development of salt-induced kidney injury and that renalase confers its cytoprotective effects by inhibiting necroptosis and inflammation.

GSDMD and GSDME synergy in the transition of acute kidney injury to chronic kidney disease

BACKGROUND AND HYPOTHESIS

Acute kidney injury (AKI) could progress to chronic kidney disease (CKD) and the AKI-CKD transition has major clinical significance. A growing body of evidence has unveiled the role of pyroptosis in kidney injury. We postulate that GSDMD and GSDME exert cumulative effects on the AKI-CKD transition by modulating different cellular responses.

METHODS

We established an AKI-CKD transition model induced by folic acid in wildtype (WT), Gsdmd-/-, Gsdme-/-, and Gsdmd-/-Gsdme-/- mice. Tubular injury, renal fibrosis and inflammatory responses were evaluated. In vitro studies were conducted to investigate the interplay among tubular cells, neutrophils, and macrophages.

RESULTS

Double deletion of Gsdmd and Gsdme conferred heightened protection against AKI, mitigating inflammatory responses, including the formation of neutrophil extracellular traps (NETs), macrophage polarization and differentiation, and ultimately renal fibrosis, compared with wildtype mice and mice with single deletion of either Gsdmd or Gsdme. Gsdme, but not Gsdmd deficiency, shielded tubular cells from pyroptosis. GSDME-dependent tubular cell death stimulated NETs formation and prompted macrophage polarization towards a pro-inflammatory phenotype. Gsdmd deficiency suppressed NETs formation and subsequently hindered NETs-induced macrophage-to-myofibroblast transition (MMT).

CONCLUSION

GSDMD and GSDME collaborate to contribute to AKI and subsequent renal fibrosis induced by folic acid. Synchronous inhibition of GSDMD and GSDME could be an innovative therapeutic strategy for mitigating the AKI-CKD transition.

Wogonin Inhibits Apoptosis and Necroptosis Induced by Nephropathogenic Infectious Bronchitis Virus in Chicken Renal Tubular Epithelial Cells

NIBV is an acute and highly contagious virus that has a major impact on the poultry industry. Wogonin, as a flavonoid drug, has antiviral effects, but there have been no reports indicating its role in renal injury caused by NIBV infection. The aim of this study is to investigate the antiviral effect of wogonin against NIBV. Renal tubular epithelial cells were isolated and cultured, and divided into four groups: Con, Con+Wog, NIBV and NIBV+Wog. We found that wogonin significantly inhibited the copy number of NIBV and significantly alleviated NIBV-induced cell apoptosis and necrosis. Moreover, wogonin inhibited the reduction in mitochondrial membrane potential and the aberrant opening of mPTP caused by NIBV. In conclusion, wogonin can protect renal tubular epithelial cells from damage by inhibiting the replication of NIBV and preventing mitochondrial apoptosis and necroptosis induced by NIBV.

Navigating the Evolving Landscape of Primary Hyperoxaluria: Traditional Management Defied by the Rise of Novel Molecular Drugs

Primary hyperoxalurias (PHs) are inherited metabolic disorders marked by enzymatic cascade disruption, leading to excessive oxalate production that is subsequently excreted in the urine. Calcium oxalate deposition in the renal tubules and interstitium triggers renal injury, precipitating systemic oxalate build-up and subsequent secondary organ impairment. Recent explorations of novel therapeutic strategies have challenged and necessitated the reassessment of established management frameworks. The execution of diverse clinical trials across various medication classes has provided new insights and knowledge. With the evolution of PH treatments reaching a new milestone, prompt and accurate diagnosis is increasingly critical. Developing early, effective management and treatment plans is essential to improve the long-term quality of life for PH patients.

Carboxymethylated Rhizoma alismatis polysaccharides reduces the risk of calcium oxalate stone formation by reducing cellular inflammation and oxidative stress

This study aims to elucidate the mechanism and potential of Rhizoma alismatis polysaccharides (RAPs) in preventing oxidative damage to human renal proximal tubule epithelial cells. The experimental approach involved incubating HK-2 cells with 100 nm calcium oxalate monohydrate for 24 h to establish a cellular injury model. Protection was provided by RAPs with varying carboxyl group contents: 3.57%, 7.79%, 10.84%, and 15.33%. The safeguarding effect of RAPs was evaluated by analyzing relevant cellular biochemical indicators. Findings demonstrate that RAPs exhibit notable antioxidative properties. They effectively diminish the release of reactive oxygen species, lactate dehydrogenase, and malondialdehyde, a lipid oxidation byproduct. Moreover, RAPs enhance superoxide dismutase activity and mitochondrial membrane potential while attenuating the permeability of the mitochondrial permeability transition pore. Additionally, RAPs significantly reduce levels of inflammatory factors, including NLRP3, TNF-α, IL-6, and NO. This reduction corresponds to the inhibition of overproduced pro-inflammatory mediator nitric oxide and the caspase 3 enzyme, leading to a reduction in cellular apoptosis. RAPs also display the ability to suppress the expression of the HK-2 cell surface adhesion molecule CD44. The observed results collectively underscore the substantial anti-inflammatory and anti-apoptotic potential of all four RAPs. Moreover, their capacity to modulate the expression of cell surface adhesion molecules highlights their potential in inhibiting the formation of kidney stones. Notably, RAP3, boasting the highest carboxyl group content, emerges as the most potent agent in this regard.

Thymol as a Potential Neuroprotective Agent: Mechanisms, Efficacy, and Future Prospects

Neurodegenerative diseases pose a growing global health challenge, with limited effective therapeutic options. Mitochondrial dysfunction, oxidative stress, neuroinflammation, apoptosis, and autophagy are common underlying mechanisms in these diseases. Thymol is a phenolic monoterpene compound that has gained attention for its diverse biological properties, including antioxidant, anti-inflammatory, and immunomodulatory activities. Thymol supplementation could provide potential neuroprotection and improve cognitive deficits, depressant-like effects, learning, and memory impairments in rodents. Mechanistic investigations reveal that the neuroprotective effects of thymol involve the improvement of oxidative stress, mitochondrial dysfunction, and inflammatory response. Several signaling pathways, including mitochondrial apoptotic, NF-κB, AKT, Nrf2, and CREB/BDNF pathways are also involved. In this review, the neuroprotective effects of thymol, the potential molecular mechanisms, safety, applications, and current challenges toward development as a neuroprotective agent were summarized and discussed. We hope that this review provides valuable insights for the further development of this promising natural product as a promising neuroprotective agent.

Clinicopathologic Characteristics, Etiologies, and Outcome of Secondary Oxalate Nephropathy

OBJECTIVE

To report the clinicopathologic characteristics, prognostic indicators, prognosis, and transplant outcome of secondary oxalate nephropathy (ON).

PATIENTS AND METHODS

We performed a retrospective analysis of 113 consecutive patients with secondary ON diagnosed at Mayo Clinic in Rochester, Minnesota, between January 1, 2001, and March 1, 2023.

RESULTS

The incidence of secondary ON among all native biopsies from Mayo Clinic patients over the study period (n=11,617) was 0.97%. ON was attributed to enteric hyperoxaluria in 60% of the 113 patients (68; most commonly Roux-en-Y gastric bypass), excessive ingestion of foods high in oxalate or oxalate precursors in 23% (26) (most commonly vitamin C), and idiopathic in 17% (19). Most patients presented with acute kidney injury (AKI) (particularly in the ingestion group) or AKI on chronic kidney disease, and 53% (60 of 113) were diabetic. Calcium oxalate crystals were accompanied by acute tubular injury, inflammation, and interstitial fibrosis and tubular atrophy. Concurrent pathologic conditions were present in 53% of the patients (60 of 113), most commonly diabetic nephropathy. After a median follow-up of 36 months, 27% of the patients (30 of 112) had kidney recovery, 19% (21 of 112) had persistent kidney dysfunction, 54% (61 of 112) had development of kidney failure, and 29% (32 of 112) died. The mean kidney survival was worse for patients with a concurrent pathologic lesion (30 months vs 96 months for those without a concurrent pathologic lesion; P<.001). Independent predictors of kidney failure were the degree of interstitial fibrosis and tubular atrophy and nadir estimated glomerular filtration rate but not the degree of crystal deposition. After a median follow-up of 58 months in 23 patients who received kidney transplant, 4 had graft loss (due to ON in 3). The 2-, 5-, and 10-year graft survivals were 90% (18 of 20), 79% (11 of 14), and 50% (6 of 12).

CONCLUSION

ON is a rare cause of AKI or AKI on chronic kidney disease. Most patients have comorbid pathologic conditions, particularly diabetic nephropathy, which worsen the prognosis. Recurrence in the renal allograft and graft loss may occur if hyperoxaluria is not controlled.

Neurologic involvement in cystinosis: Focus on brain lesions and new evidence of four-repeat (4R-) Tau immunoreactivity

Nephropathic cystinosis is a rare autosomal recessive storage disorder caused by CTNS gene mutations, leading to autophagy-lysosomal pathway impairment and cystine crystals accumulation. Neurologic involvement is highly variable and includes both neurodevelopmental and neurodegenerative disturbances, as well as focal neurologic deficits. By presenting longitudinal data of a 28-year-old patient with a large infratentorial lesion, we summarized the pathology, clinical and imaging features of neurological involvement in cystinosis patients. Brain damage in form of cystinosis-related cerebral lesions occurs in advanced disease phases and is characterized by the accumulation of cystine crystals, subsequent inflammation with vasculitis-like features, necrosis, and calcification. Epilepsy is a frequent comorbidity in affected individuals. Steroids might play a role in the symptomatic treatment of "stroke-like" episodes due to edematous-inflammatory lesions, but probably do not change the overall prognosis. Lifelong compliance to depleting therapy with cysteamine still represents the main therapeutic option. However, consequences of CTNS gene defects are not restricted to cystine accumulation. New evidence of four-repeat (4R-) Tau immunoreactivity suggests concurrent progressive neurodegeneration in cystinosis patients, highlighting the need of innovative therapeutic strategies, and shedding light on the crosstalk between proteinopathies and autophagy-lysosomal system defects. Eventually, emerging easily accessible biomarkers such as serum neurofilament light chains (NfL) might detect subclinical neurologic involvement in cystinosis patients.

VDAC1, as a downstream molecule of MLKL, participates in OGD/R-induced necroptosis by inducing mitochondrial damage

Ischemia-reperfusion (I/R) injury constitutes a significant risk factor for a range of diseases, including ischemic stroke, myocardial infarction, and trauma. Following the restoration of blood flow post-tissue ischemia, oxidative stress can lead to various forms of cell death, including necrosis, apoptosis, autophagy, and necroptosis. Recent evidence has highlighted the crucial role of mitochondrial dysfunction in I/R injury. Nevertheless, there remains much to be explored regarding the molecular signaling network governing cell death under conditions of oxidative stress. Voltage-dependent anion channel 1 (VDAC1), a major component in the outer mitochondrial membrane, is closely involved in the regulation of cell death. In a cellular model of oxygen-glucose deprivation and reoxygenation (OGD/R), which effectively simulates I/R injury in vitro, our study reveals that OGD/R induces VDAC1 oligomerization, consequently exacerbating cell death. Furthermore, we have revealed the translocation of mixed lineage kinase domain-like protein (MLKL) to the mitochondria, where it interacts with VDAC1 following OGD/R injury, leading to an increased mitochondrial membrane permeability. Notably, the inhibition of MLKL by necrosulfonamide hinders the binding of MLKL to VDAC1, primarily by affecting the membrane translocation of MLKL, and reduces OGD/R-induced VDAC1 oligomerization. Collectively, our findings provide preliminary evidence of the functional association between MLKL and VDAC1 in the regulation of necroptosis.

RIPK3 and kidney disease

Receptor interacting protein kinase 3 (RIPK3) is an intracellular kinase at the crossroads of cell death and inflammation. RIPK3 contains a RIP homotypic interaction motif (RHIM) domain which allows interactions with other RHIM-containing proteins and a kinase domain that allows phosphorylation of target proteins. RIPK3 may be activated through interaction with RHIM-containing proteins such as RIPK1, TRIF and DAI (ZBP1, DLM-1) or through RHIM-independent mechanisms in an alkaline intracellular pH. RIPK3 mediates necroptosis and promotes inflammation, independently of necroptosis, through either activation of NFκB or the inflammasome. There is in vivo preclinical evidence of the contribution of RIPK3 to both acute kidney injury (AKI) and chronic kidney disease (CKD) and to the AKI-to-CKD transition derived from RIPK3 deficient mice or the use of small molecule RIPK3 inhibitors. In these studies, RIPK3 targeting decreased inflammation but kidney injury improved only in some contexts. Clinical translation of these findings has been delayed by the potential of some small molecule inhibitors of RIPK3 kinase activity to trigger apoptotic cell death by inducing conformational changes of the protein. A better understanding of the conformational changes in RIPK3 that trigger apoptosis, dual RIPK3/RIPK1 inhibitors or repurposing of multiple kinase inhibitors such as dabrafenib may facilitate clinical development of the RIPK3 inhibition concept for diverse inflammatory diseases, including kidney diseases.

Carboxylated Pocoa polysaccharides inhibited oxidative damage and inflammation of HK-2 cells induced by calcium oxalate nanoparticles

The inhibitory effects of Chinese medicine Pocoa (PCPs) with different carboxyl group (-COOH) contents on oxidative damage and inflammatory response of renal epithelial cells and the influence of -COOH content in polysaccharides were investigated. HK-2 cell damage model was established by nanocalcium oxalate crystals (nanoCOM), and then PCPs with -COOH contents of 2.56% (PCP0), 7.48% (PCP1), 12.07% (PCP2), and 17.18% (PCP3) were used to protect the cells. PCPs could inhibit the damage of nanoCOM to HK-2 cells, increase cell viability, restore cytoskeleton and morphology, and improve lysosomal integrity. PCPs can reduce the oxidative stress response of nanoCOM to cells, inhibit the opening of mPTP and cell necrotic apoptosis, reduce the level of Ca2+ ions in cells, the production of ATP and MDA, and increase SOD expression. PCPs can also reduce the cellular inflammatory response caused by oxidative damage, and reduce the expression of nitric oxide (NO), inflammatory factors TNF-α, IL-6, IL-1β and MCP-1, as well as the content of inflammasome NLRP3. After protection, PCPs can inhibit the endocytosis of nanoCOM crystals by cells. With the increase in -COOH content in PCPs, its ability to inhibit nanoCOM cell damage, reduce oxidative stress, reduce inflammatory response, and inhibit crystal endocytosis increases, that is, PCP3 with the highest -COOH content, shows the best biological activity. Inhibiting cell damage and inflammation and reducing a large amount of endocytosis of crystals by cells are beneficial to inhibit the formation of kidney stones.

Regulated necrosis role in inflammation and repair in acute kidney injury

Acute kidney injury (AKI) frequently occurs in patients with chronic kidney disease (CKD) and in turn, may cause or accelerate CKD. Therapeutic options in AKI are limited and mostly relate to replacement of kidney function until the kidneys recover spontaneously. Furthermore, there is no treatment that prevents the AKI-to-CKD transition. Regulated necrosis has recently emerged as key player in kidney injury. Specifically, there is functional evidence for a role of necroptosis, ferroptosis or pyroptosis in AKI and the AKI-to-CKD progression. Regulated necrosis may be proinflammatory and immunogenic, triggering subsequent waves of regulated necrosis. In a paradigmatic murine nephrotoxic AKI model, a first wave of ferroptosis was followed by recruitment of inflammatory cytokines such as TWEAK that, in turn, triggered a secondary wave of necroptosis which led to persistent kidney injury and decreased kidney function. A correct understanding of the specific forms of regulated necrosis, their timing and intracellular molecular pathways may help design novel therapeutic strategies to prevent or treat AKI at different stages of the condition, thus improving patient survival and the AKI-to-CKD transition. We now review key regulated necrosis pathways and their role in AKI and the AKI-to-CKD transition both at the time of the initial insult and during the repair phase following AKI.

Multiplex gene editing reduces oxalate production in primary hyperoxaluria type 1

Targeting key enzymes that generate oxalate precursors or substrates is an alternative strategy to eliminate primary hyperoxaluria type I (PH1), the most common and life-threatening type of primary hyperoxaluria. The compact Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) from the Prevotella and Francisella 1 (Cpf1) protein simplifies multiplex gene editing and allows for all-in-one adeno-associated virus (AAV) delivery. We hypothesized that the multiplex capabilities of the Cpf1 system could help minimize oxalate formation in PH1 by simultaneously targeting the hepatic hydroxyacid oxidase 1 ( Hao1) and lactate dehydrogenase A ( Ldha) genes. Study cohorts included treated PH1 rats ( Agxt Q84X rats injected with AAV-AsCpf1 at 7 days of age), phosphate-buffered saline (PBS)-injected PH1 rats, untreated PH1 rats, and age-matched wild-type (WT) rats. The most efficient and specific CRISPR RNA (crRNA) pairs targeting the rat Hao1 and Ldha genes were initially screened ex vivo. In vivo experiments demonstrated efficient genome editing of the Hao1 and Ldha genes, primarily resulting in small deletions. This resulted in decreased transcription and translational expression of Hao1 and Ldha. Treatment significantly reduced urine oxalate levels, reduced kidney damage, and alleviated nephrocalcinosis in rats with PH1. No liver toxicity, ex-liver genome editing, or obvious off-target effects were detected. We demonstrated the AAV-AsCpf1 system can target multiple genes and rescue the pathogenic phenotype in PH1, serving as a proof-of-concept for the development of multiplex genome editing-based gene therapy.

The pathogenesis of organ fibrosis: Focus on necroptosis

Fibrosis is a common process of tissue repair response to multiple injuries in all chronic progressive diseases, which features with excessive deposition of extracellular matrix. Fibrosis can occur in all organs and tends to be nonreversible with the progress of the disease. Different cells types in different organs are involved in the occurrence and development of fibrosis, that is, hepatic stellate cells, pancreatic stellate cells, fibroblasts and myofibroblasts. Various types of programmed cell death, including apoptosis, autophagy, ferroptosis and necroptosis, are closely related to organ fibrosis. Among these programmed cell death types, necroptosis, an emerging regulated cell death type, is regarded as a huge potential target to ameliorate organ fibrosis. In this review, we summarize the role of necroptosis signalling in organ fibrosis and collate the small molecule compounds targeting necroptosis. In addition, we discuss the potential challenges, opportunities and open questions in using necroptosis signalling as a potential target for antifibrotic therapies. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

PTEN-induced kinase 1 exerts protective effects in diabetic kidney disease by attenuating mitochondrial dysfunction and necroptosis

Mitochondrial dysfunction plays a pivotal role in diabetic kidney disease initiation and progression. PTEN-induced serine/threonine kinase 1 (PINK1) is a core organizer of mitochondrial quality control; however, its function in diabetic kidney disease remains controversial. Here, we aimed to investigate the pathophysiological roles of PINK1 in diabetic tubulopathy, focusing on its effects on mitochondrial homeostasis and tubular cell necroptosis, which is a specialized form of regulated cell death. PINK1-knockout mice showed more severe diabetes-induced tubular injury, interstitial fibrosis, and albuminuria. The expression of profibrotic cytokines significantly increased in the kidneys of diabetic Pink1-/- mice, which eventually culminated in aggravated interstitial fibrosis. Additionally, the knockdown of PINK1 in HKC-8 cells upregulated the fibrosis-associated proteins, and these effects were rescued by PINK1 overexpression. PINK1 deficiency was also associated with exaggerated hyperglycemia-induced mitochondrial dysfunction and defective mitophagic activity, whereas PINK1 overexpression ameliorated these negative effects and restored mitochondrial homeostasis. Mitochondrial reactive oxygen species triggered tubular cell necroptosis under hyperglycemic conditions, which was aggravated by PINK1 deficiency and improved by its overexpression. In conclusion, PINK1 plays a pivotal role in suppressing mitochondrial dysfunction and tubular cell necroptosis under high glucose conditions and exerts protective effects in diabetic kidney disease.

Spontaneous resolution of acute gout: mechanisms and therapeutic targets

Gout is a common inflammatory arthritis that has been increasing in both prevalence and incidence. Consequently, management of refractory and chronic gout has been gaining attention. Onset of gout is related to the deposition of monosodium urate crystals under hyperuricaemia. Interestingly, acute gout attacks often resolve spontaneously within 7-10 days, and many studies have confirmed the notion that gout flares can be self-relieved. However, the underlying mechanism for spontaneous remission of gout requires further elucidation. In this article, we summarise the roles and mechanisms related to spontaneous remission of gout, which are essential for understanding its pathogenesis and developing potential targeted therapies.

Inhibition of autophagy and RIP1/RIP3/MLKL-mediated necroptosis by edaravone attenuates blood spinal cord barrier disruption following spinal cord injury

The disruption of the blood spinal cord barrier (BSCB) after spinal cord injury (SCI) can trigger secondary tissue damage. Edaravone is likely to protect the BSCB as a free radical scavenger, whereas it has been rarely reported thus far. In this study, the protective effect of edaravone was investigated with the use of compression spinal cord injured rats and human brain microvascular endothelial cells (HBMECs) injury. As indicated by the result of this study, edaravone treatment facilitated functional recovery after rats were subjected to SCI, ameliorated the vascular damage, and up-regulated the expression of BSCB-associated proteins. In vitro results, edaravone improved HBMECs viability, restored intercellular junctions, and promoted cellular angiogenic activities. It is noteworthy that autophagy was activated and RIP1/RIP3/MLKL phosphorylation was notably up-regulated. However, edaravone treatment exhibited the capability of mitigating above-mentioned tendency in vivo and in vitro. Moreover, rapamycin (Rapa) treatment deteriorated the protective effect of edaravone while aggravating the phosphorylation of RIP1/RIP3/MLKL expression. In the model of necrotic activator-induced HBMECs, autophagic expression was increased, whereas edaravone prevented autophagy and phosphorylation of RIP1/RIP3/MLKL. In general, our results suggested that edaravone is capable of reducing the destruction of BSCB and promoting functional recovery after SCI. The possible underlying mechanism is that edaravone is capable of protecting angiogenic activity and improving autophagy and the phosphorylation of RIP1/RIP3/MLKL, as well as their mutual deterioration. Accordingly, edaravone can be a favorable option for the treatment of SCI.

Oxalate (dys)Metabolism: Person-to-Person Variability, Kidney and Cardiometabolic Toxicity

Oxalate is a metabolic end-product whose systemic concentrations are highly variable among individuals. Genetic (primary hyperoxaluria) and non-genetic (e.g., diet, microbiota, renal and metabolic disease) reasons underlie elevated plasma concentrations and tissue accumulation of oxalate, which is toxic to the body. A classic example is the triad of primary hyperoxaluria, nephrolithiasis, and kidney injury. Lessons learned from this example suggest further investigation of other putative factors associated with oxalate dysmetabolism, namely the identification of precursors (glyoxylate, aromatic amino acids, glyoxal and vitamin C), the regulation of the endogenous pathways that produce oxalate, or the microbiota's contribution to oxalate systemic availability. The association between secondary nephrolithiasis and cardiovascular and metabolic diseases (hypertension, type 2 diabetes, and obesity) inspired the authors to perform this comprehensive review about oxalate dysmetabolism and its relation to cardiometabolic toxicity. This perspective may offer something substantial that helps advance understanding of effective management and draws attention to the novel class of treatments available in clinical practice.

Neutrophil extracellular traps mediate deep vein thrombosis: from mechanism to therapy

Deep venous thrombosis (DVT) is a part of venous thromboembolism (VTE) that clinically manifests as swelling and pain in the lower limbs. The most serious clinical complication of DVT is pulmonary embolism (PE), which has a high mortality rate. To date, its underlying mechanisms are not fully understood, and patients usually present with clinical symptoms only after the formation of the thrombus. Thus, it is essential to understand the underlying mechanisms of deep vein thrombosis for an early diagnosis and treatment of DVT. In recent years, many studies have concluded that Neutrophil Extracellular Traps (NETs) are closely associated with DVT. These are released by neutrophils and, in addition to trapping pathogens, can mediate the formation of deep vein thrombi, thereby blocking blood vessels and leading to the development of disease. Therefore, this paper describes the occurrence and development of NETs and discusses the mechanism of action of NETs on deep vein thrombosis. It aims to provide a direction for improved diagnosis and treatment of deep vein thrombosis in the near future.

Scaffold hopping derived novel benzoxazepinone RIPK1 inhibitors as anti-necroptosis agents

Receptor-interacting protein kinase 1 (RIPK1)-mediated necroptosis is believed to have a significant role in contributing to inflammatory diseases. Inhibiting RIPK1 has shown promise in effectively alleviating the inflammation process. In our current study, we employed scaffold hopping to develop a series of novel benzoxazepinone derivatives. Among these derivatives, compound o1 displayed the most potent antinecroptosis activity (EC50=16.17±1.878nM) in cellular assays and exhibited the strongest binding affinity to the target site. Molecular docking analyses further elucidated the mechanism of action of o1, revealing its ability to fully occupy the protein pocket and form hydrogen bonds with the amino acid residue Asp156. Our findings highlight that o1 specifically inhibits necroptosis, rather than apoptosis, by impeding the RIPK1/Receptor-interacting protein kinase 3 (RIPK3)/mixed-lineage kinase domain-like (MLKL) pathway's phosphorylation, triggered by TNFα, Smac mimetic, and z-VAD (TSZ). Additionally, o1 demonstrated dose-dependent improvements in the survival rate of mice with Systemic Inflammatory Response Syndrome (SIRS), surpassing the protective effect observed with GSK'772.

The antioxidant l-Ergothioneine prevents cystine lithiasis in the Slc7a9-/- mouse model of cystinuria

The high recurrence rate of cystine lithiasis observed in cystinuria patients highlights the need for new therapeutic options to address this chronic disease. There is growing evidence of an antioxidant defect in cystinuria, which has led to test antioxidant molecules as new therapeutic approaches. In this study, the antioxidant l-Ergothioneine was evaluated, at two different doses, as a preventive and long-term treatment for cystinuria in the Slc7a9-/- mouse model. l-Ergothioneine treatments decreased the rate of stone formation by more than 60% and delayed its onset in those mice that still developed calculi. Although there were no differences in metabolic parameters or urinary cystine concentration between control and treated mice, cystine solubility was increased by 50% in the urines of treated mice. We also demonstrate that l-Ergothioneine needs to be internalized by its transporter OCTN1 (Slc22a4) to be effective, as when administrated to the double mutant Slc7a9-/-Slc22a4-/- mouse model, no effect on the lithiasis phenotype was observed. In kidneys, we detected a decrease in GSH levels and an impairment of maximal mitochondrial respiratory capacity in cystinuric mice that l-Ergothioneine treatment was able to restore. Thus, l-Ergothioneine administration prevented cystine lithiasis in the Slc7a9-/- mouse model by increasing urinary cystine solubility and recovered renal GSH metabolism and mitochondrial function. These results support the need for clinical trials to test l-Ergothioneine as a new treatment for cystinuria.

New drug targets for the treatment of gout arthritis: what's new?

INTRODUCTION

Gout arthritis (GA) is an intermittent inflammatory disease affecting approximately 10% of the worldwide population. Symptomatic phases (acute flares) are timely spaced by asymptomatic periods. During an acute attack, redness, joint swelling, limited movement, and excruciating pain are common symptoms. However, the current available therapies are not fully effective in reducing symptoms and offer numerous side effects. Therefore, unveiling new drug targets and effector molecules are required in developing novel GA therapeutics.

AREAS COVERED

This review discusses the pathophysiological mechanisms of GA and explores potential pharmacological targets to ameliorate disease outcome. In addition, we listed promising pre-clinical studies demonstrating effector molecules with therapeutical potential. Among those, we emphasized the importance of natural products, including traditional Chinese medicine formulas and their multitarget mechanisms of action.

EXPERT OPINION

In our search, we observed that there is a massive gap between pre-clinical and clinical knowledge. Only a minority (4.4%) of clinical trials aimed to intervene by applying natural products or current hot targets described herein. In this sense, we envisage four possibilities for GA therapeutics, which include the repurposing of existing therapies, ALX/FPR2 agonism for improvement in disease outcome, the use of multitarget drugs (e.g. natural products), and targeting the neuroinflammatory component of GA.

Single-cell sequencing reveals homogeneity and heterogeneity of the cytopathological mechanisms in different etiology-induced AKI

Homogeneity and heterogeneity of the cytopathological mechanisms in different etiology-induced acute kidney injury (AKI) are poorly understood. Here, we performed single-cell sequencing (scRNA) on mouse kidneys with five common AKI etiologies (CP-Cisplatin, IRI-Ischemia-reperfusion injury, UUO-Unilateral ureteral obstruction, FA-Folic acid, and SO-Sodium oxalate). We constructed a potent multi-model AKI scRNA atlas containing 20 celltypes with 80,689 high-quality cells. The data suggest that compared to IRI and CP-AKI, FA- and SO-AKI exhibit injury characteristics more similar to UUO-AKI, which may due to tiny crystal-induced intrarenal obstruction. Through scRNA atlas, 7 different functional proximal tubular cell (PTC) subtypes were identified, we found that Maladaptive PTCs and classical Havcr1 PTCs but not novel Krt20 PTCs affect the pro-inflammatory and pro-fibrotic levels in different AKI models. And cell death and cytoskeletal remodeling events are widespread patterns of injury in PTCs. Moreover, we found that programmed cell death predominated in PTCs, whereas apoptosis and autophagy prevailed in the remaining renal tubules. We also identified S100a6 as a novel AKI-endothelial injury biomarker. Furthermore, we revealed that the dynamic and active immune (especially Arg1 Macro_2 cells) -parenchymal cell interactions are important features of AKI. Taken together, our study provides a potent resource for understanding the pathogenesis of AKI and early intervention in AKI progression at single-cell resolution.

Regulated cell death pathways in kidney disease

Disorders of cell number that result from an imbalance between the death of parenchymal cells and the proliferation or recruitment of maladaptive cells contributes to the pathogenesis of kidney disease. Acute kidney injury can result from an acute loss of kidney epithelial cells. In chronic kidney disease, loss of kidney epithelial cells leads to glomerulosclerosis and tubular atrophy, whereas interstitial inflammation and fibrosis result from an excess of leukocytes and myofibroblasts. Other conditions, such as acquired cystic disease and kidney cancer, are characterized by excess numbers of cyst wall and malignant cells, respectively. Cell death modalities act to clear unwanted cells, but disproportionate responses can contribute to the detrimental loss of kidney cells. Indeed, pathways of regulated cell death - including apoptosis and necrosis - have emerged as central events in the pathogenesis of various kidney diseases that may be amenable to therapeutic intervention. Modes of regulated necrosis, such as ferroptosis, necroptosis and pyroptosis may cause kidney injury directly or through the recruitment of immune cells and stimulation of inflammatory responses. Importantly, multiple layers of interconnections exist between different modalities of regulated cell death, including shared triggers, molecular components and protective mechanisms.

Modulatory effect of rupatadine on mesenchymal stem cell-derived exosomes in hepatic fibrosis in rats: A potential role for miR-200a

AIMS

Mesenchymal stem cell-derived exosomes (MSC-EXOs) have emerged as a promising approach in regenerative medicine for management of different diseases. However, the maintenance of their efficacy after in vivo transplantation is still a major concern. The present investigation aimed to assess the modulatory effect of rupatadine (RUP) on MSC-EXOs in diethylnitrosamine (DEN)-induced liver fibrosis (LF), and to explore the possible underlying mechanism.

MAIN METHODS

LF was induced in rats by i.p. injection of DEN (100 mg/kg) once per week for 6 successive weeks. Rats were then treated with RUP (4 mg/kg/day, p.o.) for 4 weeks with or without a single i.v. administration of MSC-EXOs. At the end of the experiment, animals were euthanized and serum and liver were separated for biochemical, and histological measurements.

KEY FINDINGS

The combined MSC-EXOs/RUP therapy provided an additional improvement towards inhibition of DEN-induced LF compared to MSC-EXOs group alone. These outcomes could be mediated through antioxidant, anti-inflammatory, and anti-fibrotic effects of RUP which created a more favorable environment for MSC-EXOs homing, and action. This in turn would enhance more effectively miR-200a expression which reduced oxidative stress, inflammation, necroptosis pathway, and subsequently fibrosis as revealed by turning off TGF-β1/α-SMA expression, and hedgehog axis.

SIGNIFICANCE

The present findings reveal that RUP enhanced the anti-fibrotic efficacy of MSC-EXOs when used as a combined therapy. This was revealed through attenuation of PAF/RIPK3/MLKL/HMGB1, and TGF-β1/hedgehog signaling pathways with a significant role for miR-200a.

A review on gout: Looking back and looking ahead

Gout is a metabolic disease caused by the deposition of monosodium urate (MSU) crystals inside joints, which leads to inflammation and tissue damage. Increased concentration of serum urate is an essential step in the development of gout. Serum urate is regulated by urate transporters in the kidney and intestine, especially GLUT9 (SLC2A9), URAT1 (SLC22A12) and ABCG. Activation of NLRP3 inflammasome bodies and subsequent release of IL-1β by monosodium urate crystals induce the crescendo of acute gouty arthritis, while neutrophil extracellular traps (NETs) are considered to drive the self-resolving of gout within a few days. If untreated, acute gout may eventually develop into chronic tophaceous gout characterized by tophi, chronic gouty synovitis, and structural joint damage, leading the crushing burden of treatment. Although the research on the pathological mechanism of gout has been gradually deepened in recent years, many clinical manifestations of gout are still unable to be fully elucidated. Here, we reviewed the molecular pathological mechanism behind various clinical manifestations of gout, with a view to making contributions to further understanding and treatment.

Proteomic analysis of sialoliths from calcified, lipid and mixed groups as a source of potential biomarkers of deposit formation in the salivary glands

Salivary stones, also known as sialoliths, are formed in a pathological situation in the salivary glands. So far, neither the mechanism of their formation nor the factors predisposing to their formation are known despite several hypotheses. While they do not directly threaten human life, they significantly deteriorate the patient's quality of life. Although this is not a typical research material, attempts are made to apply various analytical tools to characterise sialoliths and search for the biomarkers in their proteomes. In this work, we used mass spectrometry and SWATH-MS qualitative and quantitative analysis to investigate the composition and select proteins that may contribute to solid deposits in the salivary glands. Twenty sialoliths, previously characterized spectroscopically and divided into the following groups: calcified (CAL), lipid (LIP) and mixed (MIX), were used for the study. Proteins unique for each of the groups were found, including: for the CAL group among them, e.g. proteins from the S100 group (S100 A8/A12 and P), mucin 7 (MUC7), keratins (KRT1/2/4/5/13), elastase (ELANE) or stomatin (STOM); proteins for the LIP group-transthyretin (TTR), lactotransferrin (LTF), matrix Gla protein (MPG), submandibular gland androgen-regulated protein 3 (SMR3A); mixed stones had the fewest unique proteins. Bacterial proteins present in sialoliths have also been identified. The analysis of the results indicates the possible role of bacterial infections, disturbances in calcium metabolism and neutrophil extracellular traps (NETs) in the formation of sialoliths.

Die hard: cell death mechanisms and their implications in nanotoxicology

Cell death is a fundamental biological process, and its fine-tuned regulation is required for life. However, the complexity of regulated cell death is often reduced to a matter of live-dead discrimination. Here, we provide a perspective on programmed or regulated cell death, focusing on apoptosis, pyroptosis, necroptosis, and ferroptosis (the latter three cell death modalities are examples of regulated necrosis). We also touch on other, recently described manifestations of (pathological) cell death including cuproptosis. Furthermore, we address how engineered nanomaterials impact on regulated cell death. We posit that an improved understanding of nanomaterial-induced perturbations of cell death may allow for a better prediction of the consequences of human exposure and could also yield novel approaches by which to mitigate these effects. Finally, we provide examples of the harnessing of nanomaterials to achieve cancer cell killing through the induction of regulated cell death.

Autophagy and necroptosis in cisplatin-induced acute kidney injury: Recent advances regarding their role and therapeutic potential

Cisplatin (CP) is a broad-spectrum antineoplastic agent, used to treat many different types of malignancies due to its high efficacy and low cost. However, its use is largely limited by acute kidney injury (AKI), which, if left untreated, may progress to cause irreversible chronic renal dysfunction. Despite substantial research, the exact mechanisms of CP-induced AKI are still so far unclear and effective therapies are lacking and desperately needed. In recent years, necroptosis, a novel subtype of regulated necrosis, and autophagy, a form of homeostatic housekeeping mechanism have witnessed a burgeoning interest owing to their potential to regulate and alleviate CP-induced AKI. In this review, we elucidate in detail the molecular mechanisms and potential roles of both autophagy and necroptosis in CP-induced AKI. We also explore the potential of targeting these pathways to overcome CP-induced AKI according to recent advances.

Thymol Ameliorates Aspergillus fumigatus Keratitis by Downregulating the TLR4/ MyD88/ NF-kB/ IL-1β Signal Expression and Reducing Necroptosis and Pyroptosis

Fungal keratitis is a refractory kind of keratopathy. We attempted to investigate the anti-inflammatory role of thymol on Aspergillus fumigatus (A. fumigatus) keratitis. Wound healing and fluorescein staining of the cornea were applied to verify thymol's safety. Mice models of A. fumigatus keratitis underwent subconjunctival injection of thymol. The anti-inflammatory roles of thymol were verified by hematoxylin-eosin (HE) staining, slit lamp observation, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blotting. In contrast with the DMSO group, more transparent corneas and less inflammatory cells infiltration were detected in mice treated with 50 μg/ml thymol. Thymol downregulated the synthesis of TLR4, MyD88, NF-kB, IL-1β, NLRP3, caspase 1, caspase 8, GSDMD, RIPK3 and MLKL. In summary, we proved that thymol played a protective part in A. fumigatus keratitis by cutting down inflammatory cells aggregation, downregulating the TLR4/ MyD88/ NF-kB/ IL-1β signal expression and reducing necroptosis and pyroptosis.

Role of necroptosis in kidney health and disease

Cell death, particularly that of tubule epithelial cells, contributes critically to the pathophysiology of kidney disease. A body of evidence accumulated over the past 15 years has ascribed a central pathophysiological role to a particular form of regulated necrosis, termed necroptosis, to acute tubular necrosis, nephron loss and maladaptive renal fibrogenesis. Unlike apoptosis, which is a non-immunogenic process, necroptosis results in the release of cellular contents and cytokines, which triggers an inflammatory response in neighbouring tissue. This necroinflammatory environment can lead to severe organ dysfunction and cause lasting tissue injury in the kidney. Despite evidence of a link between necroptosis and various kidney diseases, there are no available therapeutic options to target this process. Greater understanding of the molecular mechanisms, triggers and regulators of necroptosis in acute and chronic kidney diseases may identify shortcomings in current approaches to therapeutically target necroptosis regulators and lead to the development of innovative therapeutic approaches.

Fetuin-A alleviates neuroinflammation against traumatic brain injury-induced microglial necroptosis by regulating Nrf-2/HO-1 pathway

BACKGROUND

The microglia-mediated inflammatory response is a vital mechanism of secondary damage following traumatic brain injury (TBI), but the underlying mechanism of microglial activation is unclear.

METHODS

Controlled cortical impact (CCI) was induced in adult male C57BL/6J mice, and glutamate was used to construct a classical in vitro injury model in the primary microglia. Microglial activation was determined by western blot and immunostaining. The inflammatory factors were measured by enzyme-linked immunosorbent assay. The oxidative stress marker and mitochondrial reactive oxygen species (ROS) were measured by immunoblotting and MitoSox Red staining. Transmission electron microscopy was used to observe the typical morphology of necroptotic cells.

RESULTS

Our quantitative proteomics identified 2499 proteins; 157 were significantly differentially expressed in brain tissue between the 6 h after CCI (CCI6h) group and sham group, and 109 were significantly differentially expressed between the CCI24h and sham groups. Moreover, compared with the sham group, the terms "acute-phase response", "inflammation", and "protein binding" were significantly enriched in CCI groups. Fetuin-A, a liver-secreted acute-phase glycoprotein, was involved in these biological processes. Using an experimental TBI model, we found that the Fetuin-A level peaked at 6 h and then decreased gradually. Importantly, we showed that administration of Fetuin-A reduced the cortical lesion volume and edema area and inhibited the inflammatory response, which was associated with suppressing microglial necroptosis, thus decreasing microglial activation. Furthermore, administration of Fetuin-A attenuated mitochondrial oxidative stress in glutamate-treated microglial cells, which is a critical mechanism of necroptosis suppression. In addition, we demonstrated that Fetuin-A treatment promoted translocation of nuclear factor erythroid 2-related factor 2 (Nrf-2) from the cytoplasm to the nucleus in vivo; however, the Nrf-2 inhibitor ML385 and si-heme oxygenase-1 (si-HO-1) disrupted the regulation of oxidative stress by Fetuin-A and induced increased ROS levels and necroptosis in glutamate-treated microglial cells. Fetuin-A also protected neurons from adverse factors in vivo and in vitro.

CONCLUSIONS

Our results demonstrated that Fetuin-A activated Nrf-2/HO-1, suppressed oxidative stress and necroptosis levels, and thereby attenuates the abnormal inflammatory response following TBI. The findings suggest a potential therapeutic strategy for TBI treatment.

Cpd-42 protects against calcium oxalate nephrocalcinosis-induced renal injury and inflammation by targeting RIPK3-mediated necroptosis

Calcium oxalate (CaOx) crystals, as the predominant component of human kidney stones, can trigger excessive cell death and inflammation of renal tubular epithelial cells, involved in the pathogenesis of nephrocalcinosis. Necroptosis mediated by receptor-interacting protein kinase 3 (RIPK3) serves a critical role in the cytotoxicity of CaOx crystals. Here, we assessed the therapeutic potential of a novel RIPK3 inhibitor, compound 42 (Cpd-42), for CaOx nephrocalcinosis by comparison with dabrafenib, a classic RIPK3 inhibitor. Our results demonstrated that Cpd-42 pretreatment attenuated CaOx crystals-induced renal tubular epithelial cell (TEC) injury by inhibiting necroptosis and inflammation in vitro and in vivo. Furthermore, in an established mouse model of CaOx nephrocalcinosis, Cpd-42 also reduced renal injury while improving the impaired kidney function and intrarenal crystal deposition. Consistent with this finding, Cpd-42 was confirmed to exhibit superior inhibition of necroptosis and protection against renal TEC injury compared to the classic RIPK3 inhibitor dabrafenib in vitro and in vivo. Mechanistically, RIPK3 knockout (KO) tubular epithelial cells pretreated with Cpd-42 did not show further enhancement of the protective effect on crystals-induced cell injury and inflammation. We confirmed that Cpd-42 exerted protective effects by specifically targeting and inhibiting RIPK3-mediated necroptosis to block the formation of the RIPK1-RIPK3 necrosome. Taken together, targeted inhibition of RIPK3-mediated necroptosis with Cpd-42 may provide a potential therapeutic approach for CaOx nephrocalcinosis.

Necroptosis: A Pathogenic Negotiator in Human Diseases

Over the past few decades, mechanisms of programmed cell death have attracted the scientific community because they are involved in diverse human diseases. Initially, apoptosis was considered as a crucial mechanistic pathway for programmed cell death; recently, an alternative regulated mode of cell death was identified, mimicking the features of both apoptosis and necrosis. Several lines of evidence have revealed that dysregulation of necroptosis leads to pathological diseases such as cancer, cardiovascular, lung, renal, hepatic, neurodegenerative, and inflammatory diseases. Regulated forms of necrosis are executed by death receptor ligands through the activation of receptor-interacting protein kinase (RIPK)-1/3 and mixed-lineage kinase domain-like (MLKL), resulting in the formation of a necrosome complex. Many papers based on genetic and pharmacological studies have shown that RIPKs and MLKL are the key regulatory effectors during the progression of multiple pathological diseases. This review focused on illuminating the mechanisms underlying necroptosis, the functions of necroptosis-associated proteins, and their influences on disease progression. We also discuss numerous natural and chemical compounds and novel targeted therapies that elicit beneficial roles of necroptotic cell death in malignant cells to bypass apoptosis and drug resistance and to provide suggestions for further research in this field.

Role of NINJ1 in Gout Flare and Potential as a Drug Target

Objective

To determine the role of nerve injury-induced protein 1 (NINJ1) introduced plasma membrane rupture (PMR) and damage-associated molecular patterns (DAMPs) release in the pathogenesis and progression of gout and to explore the potential of NINJ1 as a therapeutic target in gout.

Methods

Both peripheral blood mononuclear cells (PBMCs) and serum sample from gout patients (n = 58) and healthy controls (n = 16) were collected and processed to NINJ1 expression, lactate dehydrogenase (LDH) detection, NINJ1 inhibition, and NINJ1 expression experiments, respectively. NINJ1 knockdown was carried out by lentivirus in a monosodium urate (MSU) induced rat model, and NINJ1 neutralizing antibody was applied in a MSU induced mouse model.

Results

Our results found that NINJ1 was upregulated during a gout flare, and the resulting induction of PMR correlated with gout progression. NINJ1 knockdown significantly reduced the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome activation and joint swelling in the rat model, and NINJ1 neutralizing antibody also significantly reduced gout flare in the mouse model and PBMCs. Moreover, NINJ1 expression is under NLRP3 inflammasome produced interleukin (IL)-1β control.

Conclusion

These results support the notion of a pathogenic role of NINJ1 introduced PMR in gout and provide a detailed mechanism for gout pathogenesis involving inflammatory cell death and DAMPs release introduced by IL-1β. In addition, targeting NINJ1 might be a potential therapeutic approach for gout.

RIPK3-MLKL signaling activates mitochondrial CaMKII and drives intrarenal extracellular matrix production during CKD

Intrarenal extracellular matrix production is a prevalent feature of all forms of chronic kidney disease (CKD). The transforming growth factor-beta (TGFβ) is believed to be a major driver of extracellular matrix production. Nevertheless, anti-TGFβ therapies have consistently failed to reduce extracellular matrix production in CKD patients indicating the need for novel therapeutic strategies. We have previously shown that necroinflammation contributes to acute kidney injury. Here, we show that chronic/persistent necroinflammation drives intrarenal extracellular matrix production during CKD. We found that renal expression of receptor-interacting protein kinase-1 (RIPK1), RIPK3, and mixed lineage kinase domain-like (MLKL) increases with the expansion of intrarenal extracellular matrix production and declined kidney function in both humans and mice. Furthermore, we found that TGFβ exposure induces the translocation of RIPK3 and MLKL to mitochondria resulting in mitochondrial dysfunction and ROS production. Mitochondrial ROS activates the serine-threonine kinase calcium/calmodulin-dependent protein kinases-II (CaMKII) that increases phosphorylation of Smad2/3 and subsequent production of alpha-smooth muscle actin (αSMA), collagen (Col) 1α1, etc. in response to TGFβ during the intrarenal extracellular matrix production. Consistent with this, deficiency or knockdown of RIPK3 or MLKL as well as pharmacological inhibition of RIPK1, RIPK3, and CaMKII prevents the intrarenal extracellular matrix production in oxalate-induced CKD and unilateral ureteral obstruction (UUO). Together, RIPK1, RIPK3, MLKL, CaMKII, and Smad2/3 are molecular targets to inhibit intrarenal extracellular matrix production and preserve kidney function during CKD.

Activation of necroptosis pathway in podocyte contributes to the pathogenesis of focal segmental glomerular sclerosis

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is characterized by podocyte damage and severe proteinuria. The exact mechanism of podocyte damage and loss remains unclear. Necroptosis, a lytic form of programmed cell death mediated by RIP3 and MLKL, has emerged as an important cell death pattern in multiple tissues and cell types. Necroptosis in FSGS has not been investigated.

METHODS

Public GEO data regarding podocyte treated with vehicle or adriamycin (ADR) was identified and analyzed. Cultured human podocytes were used to explore the activation of necroptosis upon ADR stimulation. The expression of necroptosis pathway molecules, p-RIP3 and p-MLKL, was examined in the glomeruli and defoliated urinary podocytes of patients with FSGS. The effect of necroptosis inhibition was assessed in ADR-induced glomerulopathy mice using GSK872.

RESULTS

Publicly available RNA-sequencing data analysis showed that both necroptosis and NLRP3 inflammasome pathway were up-regulated in ADR-injured podocyte. Immunofluorescent staining showed increased expression of p-RIP3 and p-MLKL, the active forms of RIP3 and MLKL, in podocytes of FSGS patients and ADR-induced glomerulopathy mice but not in the normal control. GSK872, an RIP3 kinase inhibitor, significantly inhibited the expression of p-RIP3, p-MLKL and activation of NLRP3 in cultured podocytes treated with ADR. GSK872 treatment of mice with ADR-induced nephropathy resulted in the reduced expression of p-RIP3, p-MLKL, NLRP3 and caspase-1 p20. GSK872 also significantly inhibited the expression of p-MLKL in the podocytes of ADR-induced nephropathy, resulting in the attenuation of proteinuria and renal histological lesions.

CONCLUSION

Necroptosis pathway might be a valuable target for the treatment of FSGS.

CircZNF644 aggravates lipopolysaccharide-induced HK-2 cell impairment via the miR-140-5p/MLKL axis

Circular RNAs (circRNAs) play vital roles in human diseases, including acute kidney injury (AKI). In this paper, we focused on the effect of circRNA zinc finger protein 644 (circZNF644) on AKI cell model progression. qRT-PCR was conducted for the levels of circZNF644, ZNF644, miR-140-5p and mixed lineage kinase domain like pseudokinase (MLKL). RNase R assay, actinomycin D assay and subcellular fraction analysis were conducted to analyze the features of circZNF644. CCK-8 assay and EdU assay were used to explore cell proliferation. Flow cytometry analysis was conducted to analyze cell cycle and cell apoptosis. Western blot assay was executed for protein levels. ELISA was performed for the levels of inflammatory cytokines. The relationships among circZNF644, miR-140-5p and MLKL were analyzed by dual-luciferase reporter assay and RIP assay. CircZNF644 was upregulated in LPS-stimulated HK-2 cells. LPS-mediated inhibitory effects on cell proliferation and cell cycle and promotional effects on apoptosis and inflammation were reversed by circZNF644 knockdown. CircZNF644 directly interacted with miR-140-5p and MLKL was the target gene of miR-140-5p. The impact of circZNF644 knockdown on HK-2 cell injury was relieved by miR-140-5p inhibition. Moreover, miR-140-5p enhancement alleviated LPS-triggered HK-2 cell damage, while MLKL elevation reversed the effect. CircZNF644 knockdown protected HK-2 cells from LPS-induced injury by altering miR-140-5p/MLKL pathway, suggesting that circZNF644 may be a hopeful therapeutic target for AKI.

Melatonin counteracts necroptosis and pulmonary edema in cadmium-induced chronic lung injury through the inhibition of angiotensin II

The renin-angiotensin system (RAS) is an important regulator in pulmonary physiology. In our study, we identified the efficacy of melatonin to control the RAS in cadmium (Cd) induced chronic lung injury in a mouse model. Swiss albino mice exposed to CdCl₂ intraperitoneally (I.P.) (1 mg/kg b.w.; 12 weeks) showed increased release of lactate dehydrogenase in bronchoalveolar lavage fluid, generating reactive oxygen species, impaired antioxidant enzymes function, and disrupted alveolar structure along with increased expression of Angiotensin-II (Ang-II) in lung tissue. Cd-induced angiotensin-converting enzyme-2-Ang-II axis imbalance triggered the onset of Ang-II induced tumour necrosis factor alpha  (TNF-α) mediated necroptosis by upregulating the signalling molecules RIP-1, RIP-3, and p-mixed lineage kinase domain-like. In an in vitro study, colocalization of Ang-II-RIP-3 molecule in Cd intoxicated L-132 cells (human alveolar epithelial cell line), as well as pretreatment of Cd exposed cells with the inhibitor's captopril (10 μM), necrostatin-1 (50 μM), and etanercept (5 μg/ml) indicated TNF-α induced necroptotic cell death via activation of the key molecule, Ang-II. Moreover, Ang-II disrupted the alveolar-capillary barrier by decreasing tight junctional proteins (zonula occludens-1 and occludin) and endothelial VE-cadherin expression. The use of human umbilical vein endothelial cells as a model of junctional protein-expressing cells showed that captopril pretreatment (25 μM) restored VE-cadherin expression in Cd-treated human umbilical vein endothelial cells. In CdCl₂ intoxicated mice, melatonin pretreatment (10 mg/kg b.w.; 12 weeks, I.P.) inhibited inflammatory mediators (TNF-α, interleukin [IL]-1β, and IL-6) release and effectively suppressed (Cd-induced) Ang-II mediated necroptotic cell death and alveolar-capillary breaching due to Cd toxicity.

New therapeutics for primary hyperoxaluria type 1

PURPOSE OF REVIEW

Primary hyperoxaluria type 1 (PH1) is a rare genetic disorder that causes hepatic overproduction of oxalate and, often, nephrocalcinosis, nephrolithiasis, chronic kidney disease, and kidney failure. The purpose of the review is to provide an update on current emerging therapies for the treatment of PH1.

RECENT FINDINGS

Use of ribonucleic acid interference (RNAi) therapeutics that target the liver to block production of key enzymes along pathways that generate oxalate is a promising approach. Available evidence supports the efficacy of both Lumasiran (targeting glycolate oxidase) and Nedosiran (targeting hepatic lactate dehydrogenase (LDHa)) to reduce urinary oxalate excretion in PH1. The efficacy of alternative approaches including stiripentol (an anticonvulsant drug that also targets LDHa), lanthanum (a potential gastrointestinal oxalate binder), and Oxalobacter formigenes (a bacterium that can degrade oxalate within the gastrointestinal tract and may also increase its secretion from blood) are all also under study. Genetic editing tools including clustered regularly interspaced short palindromic repeats/Cas9 are also in preclinical study as a potential PH1 therapeutic.

SUMMARY

Novel treatments can reduce the plasma oxalate concentration and urinary oxalate excretion in PH1 patients. Thus, it is possible these approaches will reduce the need for combined kidney and liver transplantation to significantly decrease the morbidity and mortality of affected patients.

HDAC6 inhibition attenuates renal injury by reducing IL-1β secretion and RIP kinase mediated necroptosis in acute oxalate nephropathy

BACKGROUND

Pathogenesis of acute kidney injury is driven by necro-inflammation, which is comprised of IL-1β mediated inflammation and RIP-1 mediated tubular necroptosis. HDAC6 is reported to regulate both inflammation and cell death. In the present study, we explored the role of HDAC6 in the lysosomal exocytosis of IL-1β and RIP-1 mediated necroptosis in the context of oxalate nephropathy.

METHODS

Raw 264.7 macrophages and NRK52E stimulated with oxalate crystals and LPS with or without HDAC6 inhibitor for in vitro experiments. Acute oxalate nephropathy was induced in C57BL/6 mice by injecting sodium oxalate (75 mg/kg). For the drug intervention study, Tubastain A (TSA) was given an hour before injection of sodium oxalate. Mice were sacrificed 24 hrs after the oxalate injection, blood and kidney were harvested. Blood samples were analyzed for BUN and IL-1β levels. Renal tissues were analyzed for histology, immunohistochemistry, RNA, and protein expression.

RESULTS

HDAC6 and IL-1β upregulated in crystal stimulated macrophages and acute oxalate nephropathy. Pre-treatment of macrophages with TSA reduced IL-1β in supernatant without affecting the expression of pro-IL-1β and mature IL-1β in cell lysate. The effect of TSA on IL-1β secretion was influenced by tubulin acetylation. Renal epithelial cell NRK52E stimulated with crystals showed upregulation of necroptosis pathway markers and concentration-dependent cell death. TSA inhibited RIP-1, RIP3, and MLKL expression along with p-MLKL in stimulated epithelial cells. TSA treatment of oxalate nephropathy mice showed decreased inflammation and tubular cell death by regulating IL-1β and necroptosis and reduced renal injury.

CONCLUSION

This study highlights the role of HDAC6 in regulating the tubulin-mediated secretion of IL-1β and RIP kinase mediated necroptosis in acute oxalate nephropathy.

No Time to Die: How Kidney Cancer Evades Cell Death

The understanding of the pathogenesis of renal cell carcinoma led to the development of targeted therapies, which dramatically changed the overall survival rate. Nonetheless, despite innovative lines of therapy accessible to patients, the prognosis remains severe in most cases. Kidney cancer rarely shows mutations in the genes coding for proteins involved in programmed cell death, including p53. In this paper, we show that the molecular machinery responsible for different forms of cell death, such as apoptosis, ferroptosis, pyroptosis, and necroptosis, which are somehow impaired in kidney cancer to allow cancer cell growth and development, was reactivated by targeted pharmacological intervention. The aim of the present review was to summarize the modality of programmed cell death in the pathogenesis of renal cell carcinoma, showing in vitro and in vivo evidence of their potential role in controlling kidney cancer growth, and highlighting their possible therapeutic value.

Protective effect of bee pollen in acute kidney injury, proteinuria, and crystalluria induced by ethylene glycol ingestion in rats

Oxidative stress plays a role in hyperoxaluria-induced kidney injury and crystallization. Bee pollen is a hive product with a high content of antioxidants. The antioxidant content and protective effect of bee pollen extract (BPE) against ethylene glycol (EG) induced crystalluria, and acute kidney injury (AKI) were investigated. The effect of BPE on the EG-induced liver injury and proteinuria was also examined. Ten groups of male Wister rats were treated daily with vehicle, cystone, BPE (100, 250, and 500 mg/kg b.wt.), and group 6-9 treated with EG, EG + BPE (100, 250, and 500 mg/kg b.wt.) and group 10 EG + cystone. The dose of EG was 0.75% v/v, and the dose of cystone was 500 mg/kg b.wt. On day 30, blood and urine samples were collected for analysis. Kidneys were removed for histopathological study. The antioxidant activity of BPE was assessed, and its total phenols and flavonoids were determined. EG significantly increased urine parameters (pH, volume, calcium, phosphorus, uric acid, and protein), blood urea, creatinine, and liver enzymes (P < 0.05). EG decreased creatinine clearance and urine magnesium and caused crystalluria. Treatment with BPE or cystone mitigates EG's effect; BPE was more potent than cystone (P < 0.05). BPE increases urine volume, sodium, and magnesium compared to the control and EG treated groups. BPE reduces proteinuria and prevents AKI, crystalluria, liver injury, and histopathological changes in the kidney tissue caused by EG. BPE might have a protective effect against EG-induced AKI, crystalluria, proteinuria, and stone deposition, most likely by its antioxidant content and activity.

Microarray Profiling and Co-Expression Network Analysis of LncRNAs and mRNAs in Acute Respiratory Distress Syndrome Mouse Model

Background: Long noncoding RNAs (LncRNAs) play critical roles in many respiratory diseases. Acute respiratory distress syndrome (ARDS) is a destructive clinical syndrome of respiratory diseases. However, the potential mechanism of LncRNAs on ARDS remains largely unknown. Methods: To identify the profiles of LncRNAs and mRNAs in the LPS-induced ARDS mouse model, the microarray analyses were hired to detect the expression of LncRNAs and mRNAs in present study. Subsequently, microarray data were verified by quantitative qRT-PCR. Functional annotation on DE mRNAs and LncRNAs were carried out by bioinformatics analysis. Furthermore, the role of selected DE LncRNAs on correlated genes was confirmed by si-RNA and Western blot. Results: The expression of 2110 LncRNAs and 2690 mRNAs were significantly changed, which were further confirmed by qRT-PCR. GO and KEGG analysis indicated that the up-regulated mRNAs were mainly related to a defense response and tumor necrosis factor (TNF) signaling pathway, respectively. LncRNA-mRNA co-expression analyses showed that LncRNAs NR_003508, ENSMUST00000131638, ENSMUST00000119467, and ENSMUST00000124853 may correlate to MLKL, RIPK3, RIPK1, Caspase1, and NLRP3, respectively, or cooperatively, which were highly involved in the cell necroptosis process. Furthermore, siRNA for NR_003508 confirmed the co-expression analyses results. Conclusion: To summarize, this study implied that the DE LncRNAs could be potent regulators and target genes of ARDS and will provide a novel insight into the regulation of the pathogenesis of ARDS.

Gout-associated monosodium urate crystal-induced necrosis is independent of NLRP3 activity but can be suppressed by combined inhibitors for multiple signaling pathways

Monosodium urate (MSU) crystals, the etiological agent of gout, are formed in joints and periarticular tissues due to long-lasting hyperuricemia. Although MSU crystal-triggered NLRP3 inflammasome activation and interleukin 1β (IL-1β) release are known to have key roles in gouty arthritis, recent studies revealed that MSU crystal-induced necrosis also plays a critical role in this process. However, it remains unknown what forms of necrosis have been induced and whether combined cell death inhibitors can block such necrosis. Here, we showed that MSU crystal-induced necrosis in murine macrophages was not dependent on NLRP3 inflammasome activation, as neither genetic deletion nor pharmacological blockade of the NLRP3 pathway inhibited the necrosis. Although many cell death pathways (such as ferroptosis and pyroptosis) inhibitors or reactive oxygen species inhibitors did not have any suppressive effects, necroptosis pathway inhibitors GSK'872 (RIPK3 inhibitor), and GW806742X (MLKL inhibitor) dose-dependently inhibited MSU crystal-induced necrosis. Moreover, a triple combination of GSK'872, GW806742X, and IDN-6556 (pan-caspase inhibitor) displayed enhanced inhibition of the necrosis, which was further fortified by the addition of MCC950 (NLRP3 inhibitor), suggesting that multiple cell death pathways might have been triggered by MSU crystals. Baicalin, a previously identified inhibitor of NLRP3, inhibited MSU crystal-induced inflammasome activation and suppressed the necrosis in macrophages. Besides, baicalin gavage significantly ameliorated MSU crystal-induced peritonitis in mice. Altogether, our data indicate that MSU crystals induce NLRP3-independent necrosis, which can be inhibited by combined inhibitors for multiple signaling pathways, highlighting a new avenue for the treatment of gouty arthritis.

Inflammatory Response to Regulated Cell Death in Gout and Its Functional Implications

Gout, a chronic inflammatory arthritis disease, is characterized by hyperuricemia and caused by interactions between genetic, epigenetic, and metabolic factors. Acute gout symptoms are triggered by the inflammatory response to monosodium urate crystals, which is mediated by the innate immune system and immune cells (e.g., macrophages and neutrophils), the NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome activation, and pro-inflammatory cytokine (e.g., IL-1β) release. Recent studies have indicated that the multiple programmed cell death pathways involved in the inflammatory response include pyroptosis, NETosis, necroptosis, and apoptosis, which initiate inflammatory reactions. In this review, we explore the correlation and interactions among these factors and their roles in the pathogenesis of gout to provide future research directions and possibilities for identifying potential novel therapeutic targets and enhancing our understanding of gout pathogenesis.

Novel insights into NOD-like receptors in renal diseases

Nucleotide-binding oligomerization domain-like receptors (NLRs), including NLRAs, NLRBs (also known as NAIPs), NLRCs, and NLRPs, are a major subfamily of pattern recognition receptors (PRRs). Owing to a recent surge in research, NLRs have gained considerable attention due to their involvement in mediating the innate immune response and perpetuating inflammatory pathways, which is a central phenomenon in the pathogenesis of multiple diseases, including renal diseases. NLRs are expressed in different renal tissues during pathological conditions, which suggest that these receptors play roles in acute kidney injury, obstructive nephropathy, diabetic nephropathy, IgA nephropathy, lupus nephritis, crystal nephropathy, uric acid nephropathy, and renal cell carcinoma, among others. This review summarises recent progress on the functions of NLRs and their mechanisms in the pathophysiological processes of different types of renal diseases to help us better understand the role of NLRs in the kidney and provide a theoretical basis for NLR-targeted therapy for renal diseases.