PCSK9 causes inflammation and cGAS/STING pathway activation in diabetic nephropathy

Association between lipid-lowering drug targets and the risk of cystic kidney disease: a drug-target Mendelian randomization analysis

BACKGROUND

Evidence regarding the causal relationship between lipid-lowering drugs and cystic kidney disease, including polycystic kidney disease (PKD), was limited. This study aimed to evaluate the causal relationship between lipid phenotypes mediated by lipid-lowering drug targets-3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMGCR), proprotein convertase subtilisin/kexin type-9 (PCSK9), and Niemann-Pick C1-like 1 (NPC1L1)-and the risk of cystic kidney disease and PKD.

METHODS

Genetic variants encoding lipid-lowering drug targets-HMGCR, PCSK9, and NPC1L1-from published genome-wide association study (GWAS) statistics were collected to perform drug target Mendelian randomization (MR) analysis. Summary statistics for the GWAS of cystic kidney disease and PKD were obtained from the FinnGen consortium and the European Bioinformatics Institute. Inverse variance weighting (IVW) was used as the primary MR analysis method, with sensitivity analyses conducted to ensure the robustness of the results.

RESULTS

Increased gene expression of HMGCR was associated with an elevated risk of cystic kidney disease (IVW-MR: odds ratio [OR] = 3.05, 95% confidence interval [CI] = 1.19-7.84, p = 0.02) and PKD (IVW-MR: OR = 2.13, 95% CI = 1.01-4.46; p = 0.045). There was no evidence of causal effects of PCSK9 and NPC1L1 targets on cystic kidney disease and PKD. Cochran's Q test, MR-PRESSO, and MR-Egger intercept tests showed no heterogeneity or horizontal pleiotropy among the instrumental variables.

CONCLUSIONS

This study supported that increased HMGCR expression was associated with an increased risk of cystic kidney disease and PKD, suggesting potential benefits of statin therapy for cystic kidney disease and PKD. Further research is necessary to elucidate specific mechanisms and potential therapeutic applications of HMGCR inhibitors.

Leptin attenuates diabetic cardiomyopathy-induced cardiac remodeling via regulating cGAS/STING signaling and Opa1-mediated mitochondrial fusion

PURPOSE

This investigation seeks to elucidate the contribution of leptin to the pathogenesis of diabetic cardiomyopathy (DCM).

METHODS

Mice were rendered diabetic through the administration of streptozotocin (STZ). Leptin was delivered via subcutaneously implanted osmotic pumps. Assessments of cardiac performance, hypertrophy, and fibrosis were conducted using echocardiography, Hematoxylin and Eosin (H&E), Wheat Germ Agglutinin (WGA), and Masson trichrome staining. Myocardial apoptosis and oxidative stress were quantified through TUNEL assay and biochemical markers of oxidative stress, including Malondialdehyde (MDA), 4-Hydroxynonenal (4-HNE), and 3-Nitrotyrosine (3NT). Mitochondrial structure was examined using Transmission Electron Microscopy (TEM). Primary neonatal cardiomyocytes were subjected to high glucose (HG) conditions. The fluorescent indicators MitoTracker Green and MitoSOX Red were employed to evaluate mitochondrial morphology and function within the cardiomyocytes.

RESULTS

Mice with diabetes displayed marked cardiac hypertrophy and fibrosis, as indicated by H&E, WGA, and Masson staining. The administration of leptin significantly mitigated the cardiac pathological manifestations in diabetic mice. Leptin increased the expression of Opa1 and enhanced mitochondrial fusion and function in cardiomyocytes exposed to HG. The cGAS/STING signaling pathway may serve as a pivotal intermediary for leptin to facilitate Opa1-driven mitochondrial fusion.

CONCLUSIONS

Leptin appears to safeguard against hyperglycemia-induced mitochondrial oxidative damage and DCM by modulating the cGAS/STING signaling cascade and Opa1-mediated mitochondrial fusion. These results propose that leptin could be a promising agent for promoting mitochondrial fusion and preventing diabetes-associated cardiac pathologies.

Emerging roles of PCSK9 in kidney disease: lipid metabolism, megalin regulation and proteinuria

Chronic kidney disease (CKD) is a significant risk factor for cardiovascular disease (CVD). Key features of CKD include proteinuria and reduced glomerular filtration rate, both of which are linked to disease progression and adverse outcomes. Dyslipidemia, a major CVD risk factor, often correlates with CKD severity and is inadequately addressed by conventional therapies. Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a critical role in lipid metabolism by modulating low-density lipoprotein receptor (LDLR) levels and has emerged as a therapeutic target for managing dyslipidemia. PCSK9 inhibitors, including monoclonal antibodies and siRNA, effectively lower LDL cholesterol levels and have demonstrated safety in patients with mild to moderate CKD. Recent findings indicate that PCSK9 aggravates proteinuria by interacting with and downregulating megalin, a proximal tubule receptor essential for protein reabsorption in the kidney. Inhibition of PCSK9 has been shown to preserve megalin levels, reduce proteinuria, and improve the disease phenotype in experimental models. However, conflicting data from preclinical studies underscore the need for further research to clarify the mechanisms underlying PCSK9's role in kidney disease. This review highlights the potential of PCSK9 inhibition in addressing proteinuria and dyslipidemia in CKD, emphasizing its promise as a therapeutic strategy, while addressing current challenges and future directions for research.

Unraveling the cGAS-STING pathway in Alzheimer's disease: A new Frontier in neuroinflammation and therapeutic strategies

Alzheimer's disease (AD) is the most prevalent type of neurological disorder characterized by cognitive decline and memory loss, marked by the accumulation of amyloid beta (Aβ) plaques and hyperphosphorylated tau protein, causing extensive neuronal death and neuroinflammation. There is growing evidence that AD development extends beyond the neuronal compartment and has a major impact on the immunological functions of the brain. The cyclic GMP-AMP synthase (cGAS) detects cytosolic DNA, including pathogenic foreign DNA and self-DNA from cellular injury, triggering a type I interferon (IFN-I) response through activation of the stimulator of interferon genes (STING). The activation of the cGAS-STING pathway in response to mitochondrial dysfunction drives neuroinflammation in AD, which is mediated by the release of IFN-I cytokines. Furthermore, the release of oxidized mtDNA is necessary for the stimulation of the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome, which is a family of protein complexes that macrophages can produce to induce inflammation. AD becomes severe by the stimulation of the cGAS-STING pathway, which results in sterile inflammation and microglial dysfunction. This review aims to explore the potential impact of the cGAS-STING signaling pathway in the pathogenesis and progression of AD. Additionally; after overviewing recent findings, this article highlights the molecular mechanism involved in the onset of disease and its modulation regarding the therapeutic approach of AD. Finally, deliberated a deep insight, the cGAS-STING axis could provide novel therapeutic avenues for slowing or halting the progression of AD, thereby offering new prospects for treatment development.

Proprotein convertase subtilisin/kexin type 9 contributes to cisplatin-induced acute kidney injury by interacting with cyclase-associated protein 1 to promote megalin lysosomal degradation

Cisplatin-induced acute kidney injury (AKI) is associated with a considerable risk of mortality, highlighting the critical need for effective preventive and therapeutic strategies to mitigate its impact on patients' outcomes. Mounting evidence suggests that administration of the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor evolocumab significantly reduces the risk of AKI, however, the underlying mechanisms remain poorly understood. Megalin is an endocytic receptor that plays a crucial role in tubular cells. In this study, elevated PCSK9 expression, accompanied by decreased megalin expression, was observed in cellular and murine models of cisplatin-induced AKI. Further experiments revealed that PCSK9 overexpression downregulated megalin expression and promoted tubular injury. Additionally, the PCSK9 inhibitor evolocumab inhibited megalin loss and protected against increases in urinary protein levels, blood urea nitrogen, serum creatinine, and the kidney injury markers neutrophil gelatinase-associated lipocalin and kidney injury molecule 1. Mechanistically, PCSK9 binds to megalin and facilitates its lysosomal degradation through the coordinated actions of cyclase-associated protein 1 (CAP1) and human leukocyte antigen C (HLA-C). Similar to evolocumab, CAP1 deletion significantly protected against megalin loss and mitigated tubular injury both in vitro and in vivo. Collectively, these findings suggest that PCSK9 and CAP1 are potential therapeutic targets for patients with cisplatin-induced AKI.

PCSK9 exacerbates sevoflurane-induced neuroinflammatory response and apoptosis by up-regulating cGAS-STING signal

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a postoperative complication that can be induced by anaesthesia. PCSK9 has been shown to have a role in neuronal development and apoptosis. However, PCSK9 has not been studied in sevoflurane-induced POCD-related disorders.

OBJECTIVE

To explore whether PCSK9 can exacerbate sevoflurane-induced neuroinflammatory response and apoptosis by up-regulating cGAS-STING signalling.

METHODS

A POCD model was constructed by stimulating BV2 microglia with Sevoflurane. CCK8 was used to detect the cell viability, and immunofluorescence was used to observe the expression of microglial activation markers (Iba-1, CD11b) and BDNF to determine the activation of BV2 microglia. Cell proliferation was measured by EDU staining, and apoptosis was analyzed by flow cytometry and western blot. The levels of inflammatory cytokines, ROS, MDA, SOD and CAT were respectively detected by ELISA, DCFH-DA staining, and kits to determine the neuroinflammation and oxidative stress of cells. Mitochondrial ROS, mitochondrial membrane potential, mtDNA and ATP levels were measured to evaluate cellular mitochondrial function.

RESULTS

Transfection of si-PCSK9 inhibited Sevoflurane-induced microglial activation and restored cellular viability, promoted cell proliferation, inhibited apoptosis and neuroinflammation, decreased ROS and MDA levels in the cells while up-regulating the levels of SOD and CAT, thus inhibiting oxidative stress, restored the mitochondrial membrane potential to normal and decreased mitochondrial ROS and mtDNA levels and increased ATP production, thereby alleviating mitochondrial dysfunction. Moreover, PCSK9 depletion also down-regulated the expression of cGAS and STING to inactivate cGAS-STING signaling. However, cGAS overexpression partially reversed the effects of si-PCSK9.

CONCLUSION

PCSK9 exacerbates sevoflurane-induced neuroinflammatory response and apoptosis by upregulating cGAS-STING signaling.

Lipid abnormality in diabetic kidney disease and potential treatment advancements

Numerous studies have shown that dyslipidemia increases the risk of atherosclerotic cardiovascular disease (ASCVD) and significantly impacts the occurrence and progression of diabetic kidney disease (DKD). Early interventions for lipid metabolism disorders in DKD may improve renal function. This article reviews the clinical characteristics of dyslipidemia, mechanisms of lipid-induced renal injury, and advances in lipid-lowering therapy in DKD. We searched PubMed, Web of Science, and EMBASE to identify relevant articles, using keywords such as "diabetic kidney disease", "diabetic nephropathy", "diabetes", "dyslipidemia", "kidney", "cardiovascular disease", and "lipid therapy". High triglyceride (TG) and low high-density lipoprotein (HDL) are associated with increased risks of albuminuria and estimated glomerular filtration rate (eGFR) decline. Abnormal lipid metabolism may damage glomerular podocytes and renal tubular epithelial cells via ectopic lipid deposition, eventually impairing glomerular filtration function and increasing urinary albumin excretion. Lipid-lowering therapies can ameliorate lipid accumulation, downregulate inflammatory mediator expressions, and alleviate renal fibrosis. Fibrate and statin applications exhibit beneficial effects, reducing albuminuria and slowing eGFR decline in early DKD. However, the long-term effects of statins and fibrates on renal outcomes remain controversial. Pro-protein convertase subtilisin/kexin 9 (PCSK9)-targeted interventions have minimal side effects on the kidneys and seem effective in reducing inflammation and improving renal impairment compared with statins and fibrates. In addition, LDL apheresis (LDL-A) and double filtration plasmapheresis (DFPP) are promising clinical applications in diabetic patients with severe hypercholesterolemia or lipid-lowering drug intolerance.

Causal Association Between Cholesterol-Lowering Drugs and Diabetic Microvascular Complications: A Drug-Target Mendelian Randomization Study

Background: It remains unclear whether cholesterol-lowering therapy can reduce the incidence of microvascular complications in patients with diabetes. We aim to explore the potential causal relationship between three common types of cholesterol-lowering drugs and diabetic microvascular complications through drug-target Mendelian randomization (MR) study, laying the groundwork for the development of new medications. Methods: In this study, we collected single nucleotide polymorphisms (SNPs) associated with HMGCR (3-hydroxy-3-methylglutaryl-CoA reductase) inhibitors, PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitors, and NPC1L1 (Niemann-Pick C1-Like 1) inhibitors from published genome-wide association study statistics. Subsequently, drug-target MR analyses were performed to investigate the effects of these inhibitors on low-density lipoprotein cholesterol (LDL-C) level-mediated microvascular complications in diabetes mellitus. Coronary atherosclerosis as a positive control. Primary outcomes included diabetic nephropathy, diabetic retinopathy, and diabetic neuropathy from the FinnGen Consortium. Results: The MR analysis revealed significant associations between HMGCR inhibition and increased risks of diabetic nephropathy (OR [95%confidence interval (CI)] = 1.88 [1.50, 2.36], p = 5.55 × 10-8), retinopathy (OR [95%CI] = 1.86 [1.54, 2.24], p = 6.28 × 10-11), and neuropathy (OR [95%CI] = 2.63 [1.84, 3.75], p = 1.14 × 10-7) using the inverse variance weighted method. PCSK9 inhibitors have been associated with an increased risk of diabetic nephropathy (OR [95%CI] = 1.30 [1.07, 1.58], p = 0.009) and diabetic neuropathy (OR [95%CI] = 1.40 [1.15, 1.72], p = 0.001); NPC1L1 inhibitors significantly reduce the incidence of diabetic retinopathy (OR [95%CI] = 0.48 [0.28, 0.85], p = 0.01). The coronary heart disease as positive control. Conclusions: The findings show that HMGCR inhibitors and PCSK9 inhibitors may significantly increase the risk of diabetic microvascular complications. However, NPC1L1 inhibitors may provide protection against diabetic retinopathy.

cGAS-STING targeting offers therapy choice in lung diseases

Cyclic GMP/AMP (cGAMP) synthase (cGAS), along with the endoplasmic reticulum (ER)-associated stimulator of interferon genes (STING), are crucial elements of the type 1 interferon response. cGAS senses microbial DNA and self-DNA, labeling cGAS-STING as a crucial mechanism in autoimmunity, sterile inflammatory responses, and cellular senescence. However, chronic and aberrant activation of the cGAS-STING axis results in inflammatory and autoimmune diseases. cGAS-STING has emerged as a vital mechanism driving inflammation-related diseases, including lung diseases. Insights into the biology of the cGAS-STING pathway have enabled the discovery of small-molecule agents which have the potential to inhibit the cGAS-STING axis in lung diseases. In this review, we first outline the principal components of the cGAS-STING signaling cascade. Then, we discuss recent research that highlights general mechanisms by which cGAS-STING contributes to lung diseases. Then, we focus on summarizing a list of bioactive small-molecule compounds which inhibit the cGAS-STING pathway, reviewing their potential mechanisms.These review highlights a novel groundbreaking therapeutic possibilities through targeting cGAS-STING in lung diseases.

Mechanisms underlying the effects of the conditional knockdown of hepatic PCSK9 in attenuating lipopolysaccharide-induced acute liver inflammation

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is known to promote hyperlipidemia primarily by inducing the degradation of the low-density lipoprotein receptor. Notably, recent studies have demonstrated that PCSK9 promotes inflammation in the vascular system, however, the roles of PCSK9 in hepatic inflammation remain unclear. As PCSK9 is primarily expressed in the liver, this study aimed to elucidate the roles of PCSK9 and the underlying mechanisms in lipopolysaccharide (LPS)-challenged hepatocytes. Next-generation sequencing analysis revealed that the conditional knockdown of hepatic PCSK9 significantly reduced the plasma levels of total cholesterol and modulated the expression of hundreds of genes. Importantly, PCSK9 knockdown attenuated hepatic inflammation by suppressing several signaling pathways related to inflammation, including the Toll-like receptor, mitogen-activated protein kinase (MAPK), and phosphoinositide-3 kinase/protein kinase B pathways. This subsequently altered the expression of nuclear factor kappa-B and activator protein 1. The underlying mechanisms were further confirmed by in vitro studies using primary hepatocytes and HepG2 cells, with a p38-MAPK inhibitor, a PCSK9 antibody, and two siRNAs against PCSK9. This study is the first to report that hepatic PCSK9 knockdown ameliorates LPS-induced acute liver inflammation via modulating multiple signaling pathways, thereby suggesting therapeutic potential of PCSK9 inhibitors in treating diseases related to hepatic inflammation.

Sirtuin 2 exacerbates renal tubule injury and inflammation in diabetic mice via deacetylation of c-Jun/c-Fos

Diabetic nephropathy (DN) is a serious complication of diabetes, and inflammation plays a crucial role. Sirtuin 2 (SIRT2), a NAD+-dependent deacetylase, which is involved in the regulation of cell metabolism, proliferation and longevity through deacetylation. Our previous research showed a positive correlation between urinary SIRT2 levels and renal injury markers in DN patients. Therefore, this study explored the specific role of SIRT2 in DN and its regulatory relationship with inflammatory response. Increased expression of SIRT2 was observed in kidney tissues of DN mice and in HK2 cells induced by HG/PA. SIRT2 knockout mice alleviated microalbuminuria, inflammatory responses, and kidney damage induced by HFD/STZ. In HK2 cells, reducing SIRT2 expression or inhibiting its acetylase activity alleviated the inflammatory response induced by HG/PA, whereas overexpression of SIRT2 exacerbated this response. Further investigation revealed that SIRT2 directly interacts with c-Jun/c-Fos, promoting their deacetylation. And inhibitors of c-Jun/c-Fos partially reversed the upregulation of inflammatory factors caused by SIRT2 overexpression. Meanwhile, disrupting SIRT2 reduced the binding activity between AP-1 and the MCP-1 promoter, while overexpressing SIRT2 further increased their binding activity in HK2 cells. Interestingly, SIRT2 increased its phosphorylation while deacetylating c-Jun, leading to nuclear accumulation of p-c-Jun. In conclusion, SIRT2 knockout can alleviate kidney injury and inflammatory response in HFD/STZ mice. The mechanism is related to the increased acetylation of c-Jun/c-Fos in renal tubular epithelial cells, accompanied by crosstalk between c-Jun phosphorylation and acetylation. Blocking SIRT2 could therefore be a potential therapeutic target for DN.

Lack of renoprotective effects by long-term PCSK9 and SGLT2 inhibition using alirocumab and empagliflozin in obese ZSF1 rats

Chronic kidney disease (CKD) is associated with an increased risk of cardiovascular disease (CVD). Despite the entry of sodium glucose cotransporter 2 (SGLT2) inhibitors, CKD persists as a medical challenge. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition reduces low-density lipoprotein (LDL)-cholesterol, a major risk factor of CVD. Interestingly, studies indicate that PCSK9 inhibition decreases proteinuria in kidney disease, complementing the reduced CVD risk. This study aimed to validate obese ZSF1 rats as a model for the renoprotective effects of PCSK9 and SGLT2 inhibition using alirocumab and empagliflozin for 15 wk. Obese rats revealed a significant reduction in measured glomerular filtration rate (mGFR) and increased urine albumin/creatinine ratio (UACR) during follow-up compared with lean controls. Alirocumab treatment resulted in a decline in mGFR and increased UACR compared with vehicle-treated obese rats. Immunohistochemistry showed increased fibrosis and inflammation in kidney tissue from obese rats treated with empagliflozin or alirocumab, whereas hepatic cholesterol and triglyceride levels were lowered compared with vehicle-treated obese rats. Although alirocumab lowered circulating free cholesterol levels throughout the treatment period, certain cholesteryl esters were increased at the end of the study, resulting in no overall difference in total cholesterol levels in the alirocumab group. Correspondingly, only a trend toward increased hepatic LDL-receptor levels was observed. In conclusion, these findings suggest that alirocumab treatment aggravates kidney dysfunction in obese ZSF1 rats. Moreover, in contrast to the renoprotective properties of empagliflozin observed in patients with CKD, empagliflozin did not ameliorate kidney disease progression in the obese ZSF1 rat.NEW & NOTEWORTHY New treatments to slow kidney disease progression and reduce cardiovascular disease risk are needed for chronic kidney disease (CKD). We investigated the cholesterol-lowering PCSK9 inhibitor alirocumab as a new treatment for proteinuric CKD and the effect of SGLT2 inhibition using empagliflozin in obese ZSF1 rats. Regarding renoprotection, our findings were contradictory with previous preclinical studies and clinical data, suggesting that different pathophysiological mechanisms may apply to this rat model.

Semaglutide protects against diabetes-associated cardiac inflammation via Sirt3-dependent RKIP pathway

BACKGROUND AND PURPOSE

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) exert cardiovascular benefits in diabetic patients, but the underlying mechanisms remain incompletely understood. Semaglutide, a novel long-acting GLP-1RA, has shown a reduced risk of cardiovascular events. Based on these results, we investigated the therapeutic potential of semaglutide in diabetic cardiomyopathy and sought to elucidate the underlying mechanisms.

EXPERIMENTAL APPROACH

Mice with diabetes induced by high-fat diet/streptozotocin were treated with semaglutide. The mechanisms underlying the cardioprotective effects of semaglutide were analysed using animal and cell experiments.

KEY RESULTS

In diabetic mice, semaglutide alleviated metabolic disorders, ameliorated myocardial fibrosis, improved cardiac function, antagonized oxidative stress and suppressed cardiomyocyte apoptosis. More significantly, semaglutide attenuated cardiac inflammation through restoring Raf kinase inhibitor protein (RKIP) expression and inhibiting downstream TANK-binding kinase 1 (TBK1)-NF-κB pathway. Meanwhile, decreased RKIP expression and activated TBK1-NF-κB signalling pathway were also found in tissues from human diabetic hearts. RKIP deficiency exacerbated cardiac inflammation and offset the cardioprotective effect of semaglutide in diabetic mice. Moreover, semaglutide also restored the expression level of Sirtuin 3(Sirt3), which served as a modulator against cardiac inflammation by regulating RKIP-dependent pathway. In diabetic mice, RKIP deficiency abolished the cardioprotective benefits conferred by the Sirt3 activator honokiol. We also found that cAMP/PKA signalling, rather than glucose lowering, contributed to the anti-inflammatory effect of semaglutide through Sirt3-dependent RKIP pathway.

CONCLUSIONS AND IMPLICATIONS

Semaglutide exerted cardioprotective effects against diabetic heart failure by alleviating cardiac inflammation through Sirt3-dependent RKIP signalling pathway.

New insights of DsbA-L in the pathogenesis of metabolic diseases

Metabolic diseases, such as obesity, diabetes mellitus, and non-alcoholic fatty liver disease (NAFLD), are abnormal conditions that result from disturbances of metabolism. With the improvement of living conditions, the morbidity and mortality rates of metabolic diseases are steadily rising, posing a significant threat to human health worldwide. Therefore, identifying novel effective targets for metabolic diseases is crucial. Accumulating evidence has indicated that disulfide bond A oxidoreductase-like protein (DsbA-L) delays the development of metabolic diseases. However, the underlying mechanisms of DsbA-L in metabolic diseases remain unclear. In this review, we will discuss the roles of DsbA-L in the pathogenesis of metabolic diseases, including obesity, diabetes mellitus, and NAFLD, and highlight the potential mechanisms. These findings suggest that DsbA-L might provide a novel therapeutic strategy for metabolic diseases.

Oxidative stress and inflammatory markers in streptozotocin-induced acute and subacute toxicity response

Streptozotocin (STZ) is used as a diabetes-inducing agent in experimental animal studies. However, it is known that STZ-induced diabetic animals show significant increases in oxidative stress parameters and neurodegeneration besides their blood glucose level. In this study, the acute and subacute toxic effects of STZ on the liver, sciatic nerve, and brain tissues were investigated in vivo rat model. Sprague-Dawley rats were divided into two groups; while 50 mg/kg STZ was administered ip to the STZ group, only saline was administered to the control group. After STZ administration, three units (100 U/mL) of subcutaneous insulin glargine were applied daily to prevent the formation of diabetes. At 24 h, 1,2, and 4 weeks after applications, rats from each group were sacrificed and tissues were removed under anesthesia. At the end of the study, compared to the control, a significant decrease in SOD and GST activity and an increase in lipid peroxidation were detected in the liver and sciatic tissues of rats in the STZ-treated group in the first 24h. Considering the TUNEL, NFκB, and NOS2 expressions, it was noted that while the effects of STZ on the liver were observed in the acute stage (24h), it had subacute effects on the brain. When apoptosis-related gene expression (Bcl-2, Bax, CASP3, CASP8, CASP9, TNF-α) and immunohistochemistry were evaluated, the apoptotic effect of STZ was observed mostly in sciatic nerve tissues. Within the scope of the study, it was revealed that STZ did not only show selective toxicity to pancreatic β cells but also very toxic to other tissues and organs.

The multifaceted effects of mitochondria in kidney diseases

Mitochondria serve as the primary site for aerobic respiration within cells, playing a crucial role in maintaining cellular homeostasis. To maintain homeostasis and meet the diverse demands of the cells, mitochondria have evolved intricate systems of quality control, mainly including mitochondrial dynamics, mitochondrial autophagy (mitophagy) and mitochondrial biogenesis. The kidney, characterized by its high energy requirements, is particularly abundant in mitochondria. Interestingly, the mitochondria display complex behaviors and functions. When the kidney is suffered from obstructive, ischemic, hypoxic, oxidative, or metabolic insults, the dysfunctional mitochondrial derived from the defects in the mitochondrial quality control system contribute to cellular inflammation, cellular senescence, and cell death, posing a threat to the kidney. However, in addition to causing injury to the kidney in several cases, mitochondria also exhibit protective effect on the kidney. In recent years, accumulating evidence indicated that mitochondria play a crucial role in adaptive repair following kidney diseases caused by various etiologies. In this article, we comprehensively reviewed the current understanding about the multifaceted effects of mitochondria on kidney diseases and their therapeutic potential.

Implications of the cGAS-STING pathway in diabetes: Risk factors and therapeutic strategies

Diabetes mellitus is an increasingly prevalent metabolic disorder characterized by chronic hyperglycemia and impaired insulin action. Although the pathogenesis of diabetes is multifactorial, emerging evidence suggests that chronic low-grade inflammation plays a significant role in the development and progression of the disease. The cyclic GMP-AMP synthase (cGAS) and its downstream signaling pathway, the stimulator of interferon genes (STING), have recently gained attention in the field of diabetes research. This article aims to provide an overview of the role of cGAS-STING in diabetes, focusing on its involvement in the regulation of immune responses, inflammation, insulin resistance, and β-cell dysfunction. Understanding the contribution of cGAS-STING signaling in diabetes may lead to the development of targeted therapeutic strategies for this prevalent metabolic disorder. The results section presents key findings from multiple studies on the impact of STING in diabetes. It discusses the influence of STING on inflammation levels within a diabetic environment, its effect on insulin resistance, and its implications for the development and progression of diabetes. The cGAS-STING signaling pathway plays a crucial role in the development and progression of diabetes.

Mitophagy and cGAS-STING crosstalk in neuroinflammation

Mitophagy, essential for mitochondrial health, selectively degrades damaged mitochondria. It is intricately linked to the cGAS-STING pathway, which is crucial for innate immunity. This pathway responds to mitochondrial DNA and is associated with cellular stress response. Our review explores the molecular details and regulatory mechanisms of mitophagy and the cGAS-STING pathway. We critically evaluate the literature demonstrating how dysfunctional mitophagy leads to neuroinflammatory conditions, primarily through the accumulation of damaged mitochondria, which activates the cGAS-STING pathway. This activation prompts the production of pro-inflammatory cytokines, exacerbating neuroinflammation. This review emphasizes the interaction between mitophagy and the cGAS-STING pathways. Effective mitophagy may suppress the cGAS-STING pathway, offering protection against neuroinflammation. Conversely, impaired mitophagy may activate the cGAS-STING pathway, leading to chronic neuroinflammation. Additionally, we explored how this interaction influences neurodegenerative disorders, suggesting a common mechanism underlying these diseases. In conclusion, there is a need for additional targeted research to unravel the complexities of mitophagy-cGAS-STING interactions and their role in neurodegeneration. This review highlights potential therapies targeting these pathways, potentially leading to new treatments for neuroinflammatory and neurodegenerative conditions. This synthesis enhances our understanding of the cellular and molecular foundations of neuroinflammation and opens new therapeutic avenues for neurodegenerative disease research.

The effects of cGAS-STING inhibition in liver disease, kidney disease, and cellular senescence

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway is one of the fundamental mechanisms of the body's defense, which responds to the abnormal presence of double-stranded DNA in the cytoplasm to establish an effective natural immune response. In addition to detecting microbial infections, the cGAS pathway may be triggered by any cytoplasmic DNA, which is absent from the normal cytoplasm, and only conditions such as senescence and mitochondrial stress can lead to its leakage and cause sterile inflammation. A growing body of research has shown that the cGAS-STING pathway is strongly associated with sterile inflammation. In this study, we reviewed the regulatory mechanisms and biological functions of the cGAS-STING pathway through its involvement in aseptic inflammation in liver disease, kidney disease, and cellular senescence.

Role of mitochondrial dysfunction in kidney disease: Insights from the cGAS-STING signaling pathway

ABSTRACT

Over the past decade, mitochondrial dysfunction has been investigated as a key contributor to acute and chronic kidney disease. However, the precise molecular mechanisms linking mitochondrial damage to kidney disease remain elusive. The recent insights into the cyclic guanosine monophosphate-adenosine monophosphate (GMP-AMP) synthetase (cGAS)-stimulator of interferon gene (STING) signaling pathway have revealed its involvement in many renal diseases. One of these findings is that mitochondrial DNA (mtDNA) induces inflammatory responses via the cGAS-STING pathway. Herein, we provide an overview of the mechanisms underlying mtDNA release following mitochondrial damage, focusing specifically on the association between mtDNA release-activated cGAS-STING signaling and the development of kidney diseases. Furthermore, we summarize the latest findings of cGAS-STING signaling pathway in cell, with a particular emphasis on its downstream signaling related to kidney diseases. This review intends to enhance our understanding of the intricate relationship among the cGAS-STING pathway, kidney diseases, and mitochondrial dysfunction.

Lipid Toxicity in the Cardiovascular-Kidney-Metabolic Syndrome (CKMS)

Recent studies of Cardiovascular-Kidney-Metabolic Syndrome (CKMS) indicate that elevated concentrations of derivatives of phospholipids (ceramide, sphingosine), oxidized LDL, and lipoproteins (a, b) are toxic to kidney and heart function. Energy production for renal proximal tubule resorption of critical fuels and electrolytes is required for homeostasis. Cardiac energy for ventricular contraction/relaxation is preferentially supplied by long chain fatty acids. Metabolism of long chain fatty acids is accomplished within the cardiomyocyte cytoplasm and mitochondria by means of the glycolytic, tricarboxylic acid, and electron transport cycles. Toxic lipids and excessive lipid concentrations may inhibit cardiac function. Cardiac contraction requires calcium movement from the sarcoplasmic reticulum from a high to a low concentration at relatively low energy cost. Cardiac relaxation involves calcium return to the sarcoplasmic reticulum from a lower to a higher concentration and requires more energy consumption. Diastolic cardiac dysfunction occurs when cardiomyocyte energy conversion is inadequate. Diastolic dysfunction from diminished ATP availability occurs in the presence of inadequate blood pressure, glycemia, or lipid control and may lead to heart failure. Similar disruption of renal proximal tubular resorption of fuels/electrolytes has been found to be associated with phospholipid (sphingolipid) accumulation. Elevated concentrations of tissue oxidized low-density lipoprotein cholesterols are associated with loss of filtration efficiency at the level of the renal glomerular podocyte. Macroscopically excessive deposits of epicardial and intra-nephric adipose are associated with vascular pathology, fibrosis, and inhibition of essential functions in both heart and kidney. Chronic triglyceride accumulation is associated with fibrosis of the liver, cardiac and renal structures. Successful liver, kidney, or cardiac allograft of these vital organs does not eliminate the risk of lipid toxicity. Lipid lowering therapy may assist in protecting vital organ function before and after allograft transplantation.

Oxidative Stress: A Culprit in the Progression of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the principal culprit behind chronic kidney disease (CKD), ultimately developing end-stage renal disease (ESRD) and necessitating costly dialysis or kidney transplantation. The limited therapeutic efficiency among individuals with DKD is a result of our finite understanding of its pathogenesis. DKD is the result of complex interactions between various factors. Oxidative stress is a fundamental factor that can establish a link between hyperglycemia and the vascular complications frequently encountered in diabetes, particularly DKD. It is crucial to recognize the essential and integral role of oxidative stress in the development of diabetic vascular complications, particularly DKD. Hyperglycemia is the primary culprit that can trigger an upsurge in the production of reactive oxygen species (ROS), ultimately sparking oxidative stress. The main endogenous sources of ROS include mitochondrial ROS production, NADPH oxidases (Nox), uncoupled endothelial nitric oxide synthase (eNOS), xanthine oxidase (XO), cytochrome P450 (CYP450), and lipoxygenase. Under persistent high glucose levels, immune cells, the complement system, advanced glycation end products (AGEs), protein kinase C (PKC), polyol pathway, and the hexosamine pathway are activated. Consequently, the oxidant-antioxidant balance within the body is disrupted, which triggers a series of reactions in various downstream pathways, including phosphoinositide 3-kinase/protein kinase B (PI3K/Akt), transforming growth factor beta/p38-mitogen-activated protein kinase (TGF-β/p38-MAPK), nuclear factor kappa B (NF-κB), adenosine monophosphate-activated protein kinase (AMPK), and the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling. The disease might persist even if strict glucose control is achieved, which can be attributed to epigenetic modifications. The treatment of DKD remains an unresolved issue. Therefore, reducing ROS is an intriguing therapeutic target. The clinical trials have shown that bardoxolone methyl, a nuclear factor erythroid 2-related factor 2 (Nrf2) activator, blood glucose-lowering drugs, such as sodium-glucose cotransporter 2 inhibitors, and glucagon-like peptide-1 receptor agonists can effectively slow down the progression of DKD by reducing oxidative stress. Other antioxidants, including vitamins, lipoic acid, Nox inhibitors, epigenetic regulators, and complement inhibitors, present a promising therapeutic option for the treatment of DKD. In this review, we conduct a thorough assessment of both preclinical studies and current findings from clinical studies that focus on targeted interventions aimed at manipulating these pathways. We aim to provide a comprehensive overview of the current state of research in this area and identify key areas for future exploration.