RIPK3 blockade attenuates tubulointerstitial fibrosis in a mouse model of diabetic nephropathy

Emerging role of PANoptosis in kidney diseases: molecular mechanisms and therapeutic opportunities

Kidney diseases represent a significant global public health challenge, characterized by complex pathogenesis, high incidence, low awareness, insufficient early screening, and substantial treatment disparities. Effective therapeutic options remain lacking. Programmed cell death (PCD), including apoptosis, pyroptosis, and necroptosis, play pivotal roles in the pathogenesis of various kidney diseases. In 2019, PANoptosis, a novel form of inflammatory cell death, was introduced, providing new insights into innate immunity and PCD research. Although research on PANoptosis in kidney diseases is still limited, identifying key molecules within PANoptosomes and understanding their regulatory roles is critical for disease prevention and management. This review summarizes the various forms of PCD implicated in kidney diseases, along with PANoptosomes activated by Z-DNA binding protein 1 (ZBP1), absent in melanoma 2 (AIM2), receptor-interacting protein kinase 1 (RIPK1), NOD-like receptor family CARD domain containing 12 (NLRP12), and NOD-like receptor family member C5 (NLRC5). It also reviews the advancements in PANoptosis research in the field of kidney diseases, particularly in renal tumors and acute kidney injuries (AKI). The goal is to establish a foundation for future research into the role of PANoptosis in kidney diseases.

Effect of the glucagon-like peptide-1 receptor agonists dulaglutide on kidney outcomes in db/db mice

Diabetic kidney disease (DKD), a microvascular complication of diabetes mellitus, represents a significant clinical challenge. This study investigated the reno-protective effects of dulaglutide, a glucagon-like peptide-1 receptor agonist (GLP-1 RA) widely used in the management of diabetes, and aimed to elucidate its underlying mechanisms. Mice with db/db and db/m genotypes were allocated into four experimental groups and treated with either dulaglutide or a saline control for 10 weeks. Following the treatment period, biological samples were collected for comprehensive analysis. Serum and urinary creatinine levels were measured using a creatinine assay, while urinary protein concentrations were quantified via ELISA. Histopathological kidney damage was assessed through hematoxylin and eosin (HE) staining, with glomerular lesions evaluated using periodic acid-Schiff (PAS) staining. Inflammatory markers, ferroptosis-related indicators, and fibrosis in kidney tissues were further analyzed through PCR, Western blot (WB), immunohistochemistry (IHC), and transmission electron microscopy (TEM). Consistent with prior findings, this research demonstrated that dulaglutide improves renal function and mitigates pathological kidney damage in db/db mice. Treatment with dulaglutide significantly reduced mRNA expression of ferroptosis-related markers, including ACSL4, SLC7A11, and Ptgs2, alongside a decrease in 4-HNE levels in kidney tissues. Furthermore, dulaglutide downregulated ACSL4 protein levels and upregulated GPX4 protein expression, thereby ameliorating mitochondrial damage in renal tubular cells. In addition to these effects, dulaglutide alleviated kidney inflammation and fibrosis in db/db mice, with concomitant suppression of P-STAT3 and P-ERK expression. Collectively, these findings underscore dulaglutide's reno-protective effects in DKD, mediated through the inhibition of inflammation, improvement in renal fibrosis and ferroptosis, and modulation of P-STAT3 and P-ERK signaling pathways.

Unraveling the role of RIPKs in diabetic kidney disease and its therapeutic perspectives

Nephropathy is the microvascular complication of diabetes mellitus and is the leading cause of chronic kidney disease. This review discusses the implications of receptor-interacting protein kinase (RIPK) family members and their regulation of inflammation and cell death pathways in the initiation and progression of diabetic kidney disease. Hyperglycemia leads to reactive oxygen species (ROS) generation and RIPK1 overexpression, the first regulator of necroptosis. Further, RIPK1 can form complex I to promote nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB) and mitogen-activated protein kinase (MAPK) pathway activation or complex II to cause programmed cell death in the kidneys. The rise in RIPK1 level upon ROS generation declines the apoptosis regulators' level while the necroptosis regulators' level is boosted. Necroptosis is a programmed or controlled necrosis-type cell death pathway executed by RIPK1, RIPK3, and mixed lineage kinase domain-like (MLKL) proteins, and recent research suggests its importance in diabetic nephropathy. In necroptosis, RIPK1 and RIPK3 interrelate with their RIP homotypic interaction motif (RHIM) domains and cause the recruitment of MLKL. Next, MLKL gets oligomerized, migrate towards the plasma membrane, and causes its rupture. We emphasized different research studies on drugs highlighting the nephroprotective effects via regulating the RIPKs. We hope that the conclusions of this review may provide new strategies for diabetic kidney disease treatment and promising targets for drug development based on necroptosis.

Regulated cell death in chronic kidney disease: current evidence and future clinical perspectives

Chronic kidney disease (CKD) is the progressive loss of kidney function/structure over a period of at least 3 months. It is characterised histologically by the triad of cell loss, inflammation and fibrosis. This literature review focuses on the forms of cell death that trigger downstream inflammation and fibrosis, collectively called regulated cell death (RCD) pathways. Discrete forms of RCD have emerged as central mediators of CKD pathology. In particular, pathways of regulated necrosis - including mitochondrial permeability transition pore (mPTP)-mediated necrosis, necroptosis, ferroptosis and pyroptosis - have been shown to mediate kidney pathology directly or through the release of danger signals that trigger a pro-inflammatory response, further amplifying tissue injury in a cellular process called necroinflammation. Despite accumulating evidence in pre-clinical models, no clinical studies have yet targeted these RCD modes in human CKD. The review summarizes recent advances in our understanding of RCD pathways in CKD, looks at inter-relations between the pathways (with the emphasis on propagation of death signals) and the evidence for therapeutic targeting of molecules in the RCD pathways to prevent or treat CKD.

RIPK3 causes mitochondrial dysfunction and albuminuria in diabetic podocytopathy through PGAM5-Drp1 signaling

BACKGROUND

Receptor-interacting protein kinase (RIPK)3 is an essential molecule for necroptosis and its role in kidney fibrosis has been investigated using various kidney injury models. However, the relevance and the underlying mechanisms of RIPK3 to podocyte injury in albuminuric diabetic kidney disease (DKD) remain unclear. Here, we investigated the role of RIPK3 in glomerular injury of DKD.

METHODS

We analyzed RIPK3 expression levels in the kidneys of patients with biopsy-proven DKD and animal models of DKD. Additionally, to confirm the clinical significance of circulating RIPK3, RIPK3 was measured by ELISA in plasma obtained from a prospective observational cohort of patients with type 2 diabetes, and estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR), which are indicators of renal function, were followed up during the observation period. To investigate the role of RIPK3 in glomerular damage in DKD, we induced a DKD model using a high-fat diet in Ripk3 knockout and wild-type mice. To assess whether mitochondrial dysfunction and albuminuria in DKD take a Ripk3-dependent pathway, we used single-cell RNA sequencing of kidney cortex and immortalized podocytes treated with high glucose or overexpressing RIPK3.

RESULTS

RIPK3 expression was increased in podocytes of diabetic glomeruli with increased albuminuria and decreased podocyte numbers. Plasma RIPK3 levels were significantly elevated in albuminuric diabetic patients than in non-diabetic controls (p = 0.002) and non-albuminuric diabetic patients (p = 0.046). The participants in the highest tertile of plasma RIPK3 had a higher incidence of renal progression (hazard ratio [HR] 2.29 [1.05-4.98]) and incident chronic kidney disease (HR 4.08 [1.10-15.13]). Ripk3 knockout improved albuminuria, podocyte loss, and renal ultrastructure in DKD mice. Increased mitochondrial fragmentation, upregulated mitochondrial fission-related proteins such as phosphoglycerate mutase family member 5 (PGAM5) and dynamin-related protein 1 (Drp1), and mitochondrial ROS were decreased in podocytes of Ripk3 knockout DKD mice. In cultured podocytes, RIPK3 inhibition attenuated mitochondrial fission and mitochondrial dysfunction by decreasing p-mixed lineage kinase domain-like protein (MLKL), PGAM5, and p-Drp1 S616 and mitochondrial translocation of Drp1.

CONCLUSIONS

The study demonstrates that RIPK3 reflects deterioration of renal function of DKD. In addition, RIPK3 induces diabetic podocytopathy by regulating mitochondrial fission via PGAM5-Drp1 signaling through MLKL. Inhibition of RIPK3 might be a promising therapeutic option for treating DKD.

Research Progress of Pyroptosis in Diabetic Kidney Disease

Pyroptosis, known as one typical mode of programmed cell death, is generally characterized by the cleaved gasdermin family (GSDMs) forming pores in the cell membrane and inducing cell rupture, and the activation of aspartate-specific proteases (caspases) has also been found during this process. Diabetic Kidney Disease (DKD) is caused by the complication of diabetes in the kidney, and the most important kidney's function, Glomerular Filtration Rate (GFR), happens to drop to less than 90% of its usual and even lead to kidney failure in severe cases. The persistent inflammatory state induced by high blood glucose implies the key pathology of DKD, and growing evidence shows that pyroptosis serves as a significant contributor to this chronic immune-mediated inflammatory disorder. Currently, the expanded discovery of GSDMs, pyroptosis, and its association with innate immunity has been more attractive, and overwhelming research is needed to sort out the implication of pyroptosis in DKD pathology. In this review, we comb both classical studies and newly founds on pyroptosis, prick off the novel awakening of pyroptosis in DKD, and center on the significance of pyroptosis in DKD treatment, aiming to provide new research targets and treatment strategies on DKD.

Silencing of METTL3 prevents the proliferation, migration, epithelial-mesenchymal transition, and renal fibrosis of high glucose-induced HK2 cells by mediating WISP1 in m6A-dependent manner

Diabetic nephropathy (DN) is one of the most serious complications in diabetic patients. And m6A modifications mediated by METTL3 are involved multiple biological processes. However, the specific function and mechanism of METTL3 in DN remains unclear. DN model mice were first established with streptozotocin, and WISP1 expression was confirmed by qRT-PCR. Then the influences of WISP1 or/and METTL3 on the proliferation, migration, and epithelial-mesenchymal transition (EMT) and fibrosis-related proteins of high glucose (HG)-induced HK2 cells or HK2 cells were tested through CCK-8, wound healing, and western blot. We first revealed that WISP1 was highly expressed in renal tissues of DN model mice and HG-induced HK2 cells. Functionally, WISP1 or METTL3 silencing could weaken the proliferation, migration, EMT, and fibrosis of HG-treated HK2 cells, and WISP1 or METTL3 overexpression could induce the proliferation, migration, EMT, and fibrosis of HK2 cells. Additionally, METTL3 silencing could decrease WISP1 m6A modification, and silencing of METTL3 also could notably suppress the biological functions of HG-induced HK2 cells by downregulating WISP1. Silencing of METTL3 prevents DN development process by decreasing WISP1 with m6A modification pattern. Therefore, we suggest that METTL3/WISP1 axis might be a novel therapeutic target for DN.

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.

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.

Translation Animal Models of Diabetic Kidney Disease: Biochemical and Histological Phenotypes, Advantages and Limitations

Animal models play a crucial role in studying the pathogenesis of diseases, developing new drugs, identifying disease risk markers, and improving means of prevention and treatment. However, modeling diabetic kidney disease (DKD) has posed a challenge for scientists. Although numerous models have been successfully developed, none of them can encompass all the key characteristics of human DKD. It is essential to choose the appropriate model according to the research needs, as different models develop different phenotypes and have their limitations. This paper provides a comprehensive overview of biochemical and histological phenotypes, modeling mechanisms, advantages and limitations of DKD animal models, in order to update relevant model information and provide insights and references for generating or selecting the appropriate animal models to fit different experimental needs.

Natural products in attenuating renal inflammation via inhibiting the NLRP3 inflammasome in diabetic kidney disease

Diabetic kidney disease (DKD) is a prevalent and severe complications of diabetes and serves as the primary cause of end-stage kidney disease (ESKD) globally. Increasing evidence indicates that renal inflammation is critical in the pathogenesis of DKD. The nucleotide - binding oligomerization domain (NOD) - like receptor family pyrin domain containing 3 (NLRP3) inflammasome is the most extensively researched inflammasome complex and is considered a crucial regulator in the pathogenesis of DKD. The activation of NLRP3 inflammasome is regulated by various signaling pathways, including NF- κB, thioredoxin-interacting protein (TXNIP), and non-coding RNAs (ncRNA), among others. Natural products are chemicals extracted from living organisms in nature, and they typically possess pharmacological and biological activities. They are invaluable sources for drug design and development. Research has demonstrated that many natural products can alleviate DKD by targeting the NLRP3 inflammasome. In this review, we highlight the role of the NLRP3 inflammasome in DKD, and the pathways by which natural products fight against DKD via inhibiting the NLRP3 inflammasome activation, so as to provide novel insights for the treatment of DKD.

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.

Broadening horizons in mechanisms, management, and treatment of diabetic kidney disease

Diabetic kidney disease (DKD) is the first cause of end-stage kidney disease in patients with diabetes and its prevalence is increasing worldwide. It encompasses histological alterations that mainly affect the glomerular filtration unit, which include thickening of the basement membrane, mesangial cell proliferation, endothelial alteration, and podocyte injury. These morphological abnormalities further result in a persistent increase of urinary albumin-to-creatinine ratio and in a reduction of the estimated glomerular filtration rate. Several molecular and cellular mechanisms have been recognized, up to date, as major players in mediating such clinical and histological features and many more are being under investigation. This review summarizes the most recent advances in understanding cell death mechanisms, intracellular signaling pathways and molecular effectors that play a role in the onset and progression of diabetic kidney damage. Some of those molecular and cellular mechanisms have been already successfully targeted in preclinical models of DKD and, in some cases, strategies have been tested in clinical trials. Finally, this report sheds light on the relevance of novel pathways that may become therapeutic targets for future applications in DKD.

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.

Investigating the role of receptor interacting protein kinase 3 in venous thrombosis

Objective

Venous thromboembolism is a disease that encompasses both deep vein thrombosis and pulmonary embolism. Recent investigations have shown that receptor interacting protein kinase 3 (RIPK3), a protein known for its role in the programmed form of cell death necroptosis, may play a role in thrombosis. Specifically, RIPK3 has been shown to promote platelet activation in arterial thrombosis and mixed lineage kinase domain-like pseudokinase (MLKL), a protein downstream of RIPK3 in the necroptosis pathway, has been shown to promote neutrophil extracellular trap formation in deep vein thrombosis. This investigation sought to comprehensively investigate the role of RIPK3 in deep vein thrombogenesis.

Methods

The inferior vena cava ligation and stenosis models of deep vein thrombosis were used in C57BL/6J, RIPK3 wild-type (Ripk3 ^+/+ ) and RIPK3-deficient (Ripk3 ^-/- ) mice. Downstream tissue analyses included measurement of thrombus weight and histological and Western blot analysis of tissues for markers of necroptosis and cell death. A subset of C57BL/6J mice were treated with a RIPK3 inhibitor to determine the effect on venous thrombosis.

Results

C57BL/6J mice showed significant increases in thrombus weight from 6 to 48 hours. During the same time frame, RIPK3 progressively accumulated in the vein wall (a 35-fold increase from 0 to 48 hours). RIPK3 was present in the thrombus; however, it decreased with time. Although present in the thrombus, MLKL was nearly undetectable in the vein wall by Western blot at any timepoint. Immunostaining confirmed the high accumulation of RIPK3 in the vein wall, primarily colocalized to endothelial and smooth muscle cells. Phosphorylated MLKL, the active form of MLKL and executioner of necroptotic cell death, was detectable by immunostaining in the thrombus, but was present at low to undetectable levels in the vein wall. Propidium iodide and terminal deoxynucleotidyl transferase dUTP nick end labeling staining revealed a high burden of necrotic and apoptotic cells within the thrombus at 48 hours, but a relatively lower burden within the vein wall. Despite robust accumulation of RIPK3 within the vessel wall and the thrombus, knockout and inhibition of RIPK3 failed to impact thrombus incident or weight at 48 hours after inferior vena cava ligation. Neutrophil extracellular trap burden did not differ between Ripk3 ^+/+ and Ripk3 ^-/- mice.

Conclusions

In mice, the vein wall responded to deep vein thrombosis induction with elevation of RIPK3 without showing markers of necroptosis and apoptosis. Studies using genetic or pharmacological inhibition of RIPK3 suggest that this cell death mediator may not have a major role in the acute phase of venous thrombogenesis. Further investigation is needed to determine if RIPK3 plays a potentially non-necroptotic role within the vein wall during later stages of thrombus resolution and vein wall remodeling.

Low-dose hydralazine reduces albuminuria and glomerulosclerosis in a mouse model of obesity-related chronic kidney disease

AIM

To determine, using a mouse model of obesity, whether low-dose hydralazine prevents obesity-related chronic kidney disease (CKD).

METHODS

From 8 weeks of age, male C57BL/6 mice received a high-fat diet (HFD) or chow, with or without low-dose hydralazine (25 mg/L) in drinking water, for 24 weeks. Biometric and metabolic variables, renal function and structural changes, renal global DNA methylation, DNA methylation profile and markers of renal fibrosis, injury, inflammation and oxidative stress were assessed.

RESULTS

The HFD-fed mice developed obesity, with glucose intolerance, hyperinsulinaemia and dyslipidaemia. Obesity increased albuminuria and glomerulosclerosis, which were significantly ameliorated by low-dose hydralazine in the absence of a blood pressure-lowering effect. Obesity increased renal global DNA methylation and this was attenuated by low-dose hydralazine. HFD-induced changes in methylation of individual loci were also significantly reversed by low-dose hydralazine. Obese mice demonstrated increased markers of kidney fibrosis, inflammation and oxidative stress, but these markers were not significantly improved by hydralazine.

CONCLUSION

Low-dose hydralazine ameliorated HFD-induced albuminuria and glomerulosclerosis, independent of alterations in biometric and metabolic variables or blood pressure regulation. Although the precise mechanism of renoprotection in obesity is unclear, an epigenetic basis may be implicated. These data support repurposing hydralazine as a novel therapy to prevent CKD progression in obese patients.

Baicalin inhibits necroptosis by decreasing oligomerization of phosphorylated MLKL and mitigates caerulein-induced acute pancreatitis in mice

Necroptosis is a form of regulated necrosis mainly controlled by receptor-interacting protein kinases 3 (RIPK3) and mixed lineage kinase domain-like protein (MLKL). Necroptosis has important roles in defensing against pathogenic infections, but it is also implicated in various inflammatory diseases including pancreatitis. Baicalin, a flavonoid from Scutellaria baicalensis Georgi, has been shown to possess anti-inflammatory and anti-pyroptosis properties, yet it is unclear whether baicalin can inhibit necroptosis and confer protection against necroptosis-related diseases. Here we reported that baicalin significantly inhibited necroptosis in macrophages induced by lipopolysaccharide plus pan-caspase inhibitor (IDN-6556), or by tumor-necrosis factor-α in combination with LCL-161 (Smac mimetic) and IDN-6556 (TSI). Mechanistically, baicalin did not inhibit the phosphorylation of RIPK1, RIPK3 and MLKL, nor membrane translocation of p-MLKL, during necroptotic induction, but instead inhibited p-MLKL oligomerization that is required for executing necroptosis. As intracellular reactive oxygen species (ROS) has been reported to be involved in p-MLKL oligomerization, we assessed the effects of N-acetyl-L-cysteine (NAC), an ROS scavenger, on necroptosis and found that NAC significantly attenuated TSI-induced necroptosis and intracellular ROS production concomitantly with reduced levels of oligomerized p-MLKL, mirroring the effect of baicalin. Indeed, inhibitory effect of baicalin was associated with reduced TSI-induced superoxide (indicating mitochondrial ROS) production and increased mitochondrial membrane potential within cells during necroptosis. Besides, oral administration of baicalin significantly reduced the severity of caerulein-induced acute pancreatitis in mice, an animal model of necroptosis-related disease. Collectively, baicalin can inhibit necroptosis through attenuating p-MLKL oligomerization and confers protection against caerulein-induced pancreatitis in mice.

Receptor-Interacting Protein Kinase 3 Inhibition Relieves Mechanical Allodynia and Suppresses NLRP3 Inflammasome and NF-κB in a Rat Model of Spinal Cord Injury

Background

Neuroinflammation is critical in developing and maintaining neuropathic pain after spinal cord injury (SCI). The receptor-interacting protein kinase 3 (RIPK3) has been shown to promote inflammatory response by exerting its non-necroptotic functions. In this study, we explored the involvement of RIPK3 in neuropathic pain after SCI.

Methods

Thoracic (T10) SCI rat model was conducted, and the mechanical threshold in rats was measured. The expressions of RIPK3, nod-like receptor family pyrin domain-containing protein 3 (NLRP3), caspase-1, and nuclear factor-κB (NF-κB) were measured with western blotting analysis or quantitative real-time polymerase chain reaction (qRT-PCR). Double immunofluorescence staining was used to explore the colabeled NLRP3 with NeuN, glial fibrillary acidic protein (GFAP), and ionized calcium-binding adapter molecule 1 (IBA1). In addition, enzyme-linked immunosorbent assay (ELISA) was applied to analyze the levels of proinflammatory factors interleukin 1 beta (IL-1β), interleukin 18 (IL-18), and tumor necrosis factor alpha (TNF-α).

Results

The expression of RIPK3 was elevated from postoperative days 7–21, which was consistent with the development of mechanical allodynia. Intrathecal administration of RIPK3 inhibitor GSK872 could alleviate the mechanical allodynia in SCI rats and reduce the expression levels of RIPK3. The activation of NLRP3 inflammasome and NF-κB was attenuated by GSK872 treatment. Furthermore, immunofluorescence suggested that NLRP3 had colocalization with glial cells and neurons in the L4–L6 spinal dorsal horns. In addition, GSK872 treatment reduced the production of inflammatory cytokines.

Conclusion

Our findings indicated that RIPK3 was an important facilitated factor for SCI-induced mechanical allodynia. RIPK3 inhibition might relieve mechanical allodynia by inhibiting NLRP3 inflammasome, NF-κB, and the associated inflammation.

Bone Marrow-Derived RIPK3 Mediates Kidney Inflammation in Acute Kidney Injury

BACKGROUND

Receptor-interacting protein kinase 3 (RIPK3), a component of necroptosis pathways, may have an independent role in inflammation. It has been unclear which RIPK3-expressing cells are responsible for the anti-inflammatory effect of overall Ripk3 deficiency and whether Ripk3 deficiency protects against kidney inflammation occurring in the absence of tubular cell death.

METHODS

We used chimeric mice with bone marrow from wild-type and Ripk3-knockout mice to explore RIPK3's contribution to kidney inflammation in the presence of folic acid-induced acute kidney injury AKI (FA-AKI) or absence of AKI and kidney cell death (as seen in systemic administration of the cytokine TNF-like weak inducer of apoptosis [TWEAK]).

RESULTS

Tubular and interstitial cell RIPK3 expressions were increased in murine AKI. Ripk3 deficiency decreased NF-κB activation and kidney inflammation in FA-AKI but did not prevent kidney failure. In the chimeric mice, RIPK3-expressing bone marrow-derived cells were required for early inflammation in FA-AKI. The NLRP3 inflammasome was not involved in RIPK3's proinflammatory effect. Systemic TWEAK administration induced kidney inflammation in wild-type but not Ripk3-deficient mice. In cell cultures, TWEAK increased RIPK3 expression in bone marrow-derived macrophages and tubular cells. RIPK3 mediated TWEAK-induced NF-κB activation and inflammatory responses in bone marrow-derived macrophages and dendritic cells and in Jurkat T cells; however, in tubular cells, RIPK3 mediated only TWEAK-induced Il-6 expression. Furthermore, conditioned media from TWEAK-exposed wild-type macrophages, but not from Ripk3-deficient macrophages, promoted proinflammatory responses in cultured tubular cells.

CONCLUSIONS

RIPK3 mediates kidney inflammation independently from tubular cell death. Specific targeting of bone marrow-derived RIPK3 may limit kidney inflammation without the potential adverse effects of systemic RIPK3 targeting.

Sexual Effect of Platelet-to-Lymphocyte Ratio in Predicting Cardiovascular Mortality of Peritoneal Dialysis Patients

BACKGROUND

The study is aimed at exploring the relationship of platelet-to-lymphocyte (PLR), all-cause, and cardiovascular disease (CVD) mortality in peritoneal dialysis (PD) patients based on gender.

METHODS

A total of 1438 PD patients from January 1,2007 to December 31, 2014 in PD center at The First Affiliated Hospital, Sun Yat-sen University, were included. Patients were followed up until December 31, 2019. The endpoint was all-cause mortality and CVD mortality. Cox proportional hazards regression models were used to evaluate the association of PLR with all-cause and CVD mortality to calculate hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

After a median of 48.9 (interquartile range [IQR]: 23.4-79.3) months of follow-up, 406 (28.2%) patients died based on all-cause death, among which 200 (49.3%) patients died from CVD. In the multivariate Cox regression model, we found that PLR was independently related to an increased risk of CVD mortality only in female PD patients, with HR of 1.003 (95% CI: 1.001-1.006). Interaction test showed that the correlation between PLR level for all-cause and CVD mortality varied with gender (p = 0.042 and p = 0.012, respectively).

CONCLUSION

Higher PLR was associated with a higher risk of CVD mortality in female PD patients.

Metabolic Dysfunction in the Regulation of the NLRP3 Inflammasome Activation: A Potential Target for Diabetic Nephropathy

Metabolic dysfunction plays a key role in the development of diabetic nephropathy (DN). However, the exact effects and mechanisms are still unclear. The pyrin domain-containing protein 3 (NLRP3) inflammasome, a member of the nod-like receptor family, is considered a crucial inflammatory regulator and plays important roles in the progress of DN. A growing body of evidence suggests that high glucose, high fat, or other metabolite disorders can abnormally activate the NLRP3 inflammasome. Thus, in this review, we discuss the potential function of abnormal metabolites such as saturated fatty acids (SFAs), cholesterol crystals, uric acid (UA), and homocysteine in the NLRP3 inflammasome activation and explain the potential function of metabolic dysfunction regulation of NLRP3 activation in the progress of DN via regulation of inflammatory response and renal interstitial fibrosis (RIF). In addition, the potential mechanisms of metabolism-related drugs, such as metformin and sodium glucose cotransporter (SGLT2) inhibitors, which have served as the suppressors of the NLRP3 inflammasomes, in DN, are also discussed. A better understanding of NLRP3 inflammasome activation in abnormal metabolic microenvironment may provide new insights for the prevention and treatment of DN.

Pyroptosis in diabetic nephropathy

Diabetic nephropathy (DN), a sterile inflammatory disease, is a serious complication of diabetes mellitus. However, recent evidence indicates that pyroptosis, a new term for pro-inflammatory cell death featured by gasdermin D (GSDMD)-stimulated plasma membrane pore generation, cell expansion and rapid lysis with the extensive secretion of pro-inflammatory factors, including interleukin-1β (IL-1β) and -18 (IL-18) may be involved in DN. Caspase-1-induced canonical and caspase-4/5/11-induced non-canonical inflammasome-signaling pathways are mainly believed to participate in pyroptosis-mediated cell death. Further research has uncovered that activation of the caspase-3/8 signaling pathway may also activate pyroptosis. Accumulating evidence has shown that NLRP3 inflammasome activation plays a critical role in promoting the pathogenesis of DN. In addition, current studies have suggested that pyroptosis-induced cell death promotes several diabetic complications that include DN. Our present study briefs the cellular mechanisms of pyroptosis-related signaling pathways and their impact on the promotion of DN. In this review, several investigational compounds suppressing pyroptosis-mediated cell death are explored as promising therapeutics in DN.

NLRP3 inflammasome activation and cell death

The NLRP3 inflammasome is a cytosolic multiprotein complex composed of the innate immune receptor protein NLRP3, adapter protein ASC, and inflammatory protease caspase-1 that responds to microbial infection, endogenous danger signals, and environmental stimuli. The assembled NLRP3 inflammasome can activate the protease caspase-1 to induce gasdermin D-dependent pyroptosis and facilitate the release of IL-1β and IL-18, which contribute to innate immune defense and homeostatic maintenance. However, aberrant activation of the NLRP3 inflammasome is associated with the pathogenesis of various inflammatory diseases, such as diabetes, cancer, and Alzheimer's disease. Recent studies have revealed that NLRP3 inflammasome activation contributes to not only pyroptosis but also other types of cell death, including apoptosis, necroptosis, and ferroptosis. In addition, various effectors of cell death have been reported to regulate NLRP3 inflammasome activation, suggesting that cell death is closely related to NLRP3 inflammasome activation. In this review, we summarize the inextricable link between NLRP3 inflammasome activation and cell death and discuss potential therapeutics that target cell death effectors in NLRP3 inflammasome-associated diseases.

LncRNA SNHG15 relieves hyperglycemia-induced endothelial dysfunction via increased ubiquitination of thioredoxin-interacting protein

Numerous studies have revealed that hyperglycemia is a pivotal driver of diabetic vascular complications. However, the mechanisms of hyperglycemia-induced endothelial dysfunction in diabetes remain incompletely understood. This study aims to expound on the underlying mechanism of the endothelial dysfunction induced by hyperglycemia from the perspective of long non-coding RNAs (lncRNA). In this study, a downregulation of SNHG15 was observed in the ischemic hind limb of diabetic mice and high glucose (HG)-treated HUVECs. Functionally, the overexpression of SNHG15 promoted cell proliferation, migration, and tube formation, and suppressed cell apoptosis in HG-treated HUVECs. Mechanistically, SNHG15 reduced thioredoxin-interacting protein (TXNIP) expression by enhancing ITCH-mediated ubiquitination of TXNIP. TXNIP overexpression abrogated the protective effect of lncRNA SNHG15 overexpression on HG-induced endothelial dysfunction. The following experiment further confirmed that SNHG15 overexpression promoted angiogenesis of the ischemic hind limb in diabetic mice. In conclusion, SNHG15 is a novel protector for hyperglycemia-induced endothelial dysfunction via decreasing TXNIP expression.

Gene expression profiles of diabetic kidney disease and neuropathy in eNOS knockout mice: Predictors of pathology and RAS blockade effects

Diabetic kidney disease (DKD) and diabetic peripheral neuropathy (DPN) are two common diabetic complications. However, their pathogenesis remains elusive and current therapies are only modestly effective. We evaluated genome-wide expression to identify pathways involved in DKD and DPN progression in db/db eNOS-/- mice receiving renin-angiotensin-aldosterone system (RAS)-blocking drugs to mimic the current standard of care for DKD patients. Diabetes and eNOS deletion worsened DKD, which improved with RAS treatment. Diabetes also induced DPN, which was not affected by eNOS deletion or RAS blockade. Given the multiple factors affecting DKD and the graded differences in disease severity across mouse groups, an automatic data analysis method, SOM, or self-organizing map was used to elucidate glomerular transcriptional changes associated with DKD, whereas pairwise bioinformatic analysis was used for DPN. These analyses revealed that enhanced gene expression in several pro-inflammatory networks and reduced expression of development genes correlated with worsening DKD. Although RAS treatment ameliorated the nephropathy phenotype, it did not alter the more abnormal gene expression changes in kidney. Moreover, RAS exacerbated expression of genes related to inflammation and oxidant generation in peripheral nerves. The graded increase in inflammatory gene expression and decrease in development gene expression with DKD progression underline the potentially important role of these pathways in DKD pathogenesis. Since RAS blockers worsened this gene expression pattern in both DKD and DPN, it may partly explain the inadequate therapeutic efficacy of such blockers.

LncRNA SNHG15 relieves hyperglycemia-induced endothelial dysfunction via increasing ubiquitination of thioredoxin-interacting protein

OBJECTIVE

Numerous evidence indicates that hyperglycemia is a pivotal driver of the vascular complications of diabetes. However, the mechanisms of hyperglycemia-induced endothelial dysfunction in diabetes remain incompletely understood. This study aims to expound on the underlying mechanism of the endothelial dysfunction induced by hyperglycemia from the perspective of long non-coding RNAs (lncRNA).

MATERIALS AND METHODS

Cell proliferation, migration, apoptosis, and tube formation were measured by cell counting kit-8 assay, transwell assay, flow cytometry, and tube formation assay, respectively. RNA pull-down and RNA-binding protein immunoprecipitation were used to detect the interaction between lncRNA SNHG15 and thioredoxin-interacting protein (TXNIP). Co-immunoprecipitation was used to detect the ubiquitination level of TXNIP and the interaction between TXNIP and E3 ubiquitin ligase ITCH.

RESULTS

A downregulation of SNHG15 was observed in the ischemic hind limb of diabetic mice and high glucose (HG)-treated HUVECs. Functionally, the overexpression of SNHG15 promoted cell proliferation, migration, and tube formation, and suppressed cell apoptosis in HG-treated HUVECs. Mechanically, SNHG15 reduced TXNIP expression by enhancing ITCH-mediated ubiquitination of TXNIP. TXNIP overexpression abrogated the protective effect of LncRNA SNHG15 overexpression on HG-induced endothelial dysfunction. The following experiment further confirmed that SNHG15 overexpression promoted angiogenesis of the ischemic hind limb in diabetic mice.

CONCLUSION

SNHG15 is a novel protector for hyperglycemia-induced endothelial dysfunction via decreasing TXNIP expression.

Ursolic acid reverses liver fibrosis by inhibiting NOX4/NLRP3 inflammasome pathways and bacterial dysbiosis

Activation of the NOX4/NLRP3 inflammasome pathway has been associated with fibrosis in other organs. An imbalance in intestinal bacteria is an important driving factor of liver fibrosis through the liver-gut axis. This study aimed to explore whether the effect of ursolic acid (UA) on liver fibrosis was associated with the NOX4/NLRP3 inflammasome pathways and intestinal bacteria. Wild-type (WT), NLRP3-/-, and NOX4-/- mice and AP-treated mice were injected with CCI4 and treated with or without UA. The intestinal contents of the mice were collected and analyzed by 16S rRNA sequencing. UA alleviated liver fibrosis, which manifested as decreases in collagen deposition, liver injury, and the expression of fibrosis-related factors, and the expression of NOX4 and NLRP3 was significantly inhibited by UA treatment. Even after CCI4 injection, liver damage and fibrosis-related factors were significantly decreased in NLRP3-/-, NOX4-/-, and AP-treated mice. Importantly, the expression of NLRP3 was obviously inhibited in NOX4-/- and AP-treated mice. In addition, the diversity of intestinal bacteria and the abundance of probiotics in NLRP3-/- and NOX4-/- mice was significantly higher than those in WT mice, while the abundance of harmful bacteria in NLRP3-/- and NOX4-/- mice was significantly lower than that in WT mice. The NOX4/NLRP3 inflammasome pathway plays a crucial role in liver fibrosis and is closely associated with the beneficial effect of UA. The mechanism by which the NOX4/NLRP3 inflammasome pathway is involved in liver fibrosis may be associated with disordered intestinal bacteria.

Chrysophanol Inhibits the Progression of Diabetic Nephropathy via Inactivation of TGF-β Pathway

Background

Diabetic nephropathy (DN) is a common form of diabetic complication which threatens the health of patients with diabetes. It has been reported that chrysophanol (CHR) can alleviate the progression of diabetes; however, the role of CHR in DN remains unclear.

Methods

To mimic DN in vitro, human podocytes (AB8/13 cells) were treated with high glucose (HG). Meanwhile, Western blot was performed to detect protein expressions. CCK-8 assay was used to test cell viability and cell proliferation was detected by Ki-67 staining. In addition, flow cytometry was performed to investigate cell apoptosis and cycle and cell migration was tested by transwell assay. Moreover, in vivo model of DN was established to detect the effect of CHR on DN in vivo.

Results

HG-induced AB8/13 cell growth inhibition was significantly rescued by CHR. In addition, HG notably promoted the migration of AB8/13 cells, while this phenomenon was obviously reversed by CHR. Moreover, CHR inhibited the progression of DN via inactivation of TGF-β/EMT axis. Furthermore, CHR alleviated the symptom of DN in vivo.

Conclusion

CHR significantly alleviated the progression of DN via inactivation of TGF-β/EMT signaling in vitro and in vivo. Our findings were helpful to uncover the mechanism by which CHR regulates DN, as well as inspire the development of novel therapy against DN.