Protective effect of silencing Stat1 on high glucose-induced podocytes injury via Forkhead transcription factor O1-regulated the oxidative stress response

Immunometabolism mRNA expression phenotypes and reprogramming of CD14 in T2DM with or without CVD

BACKGROUND/AIM

Type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVD) have a significant impact on the expression of genes in peripheral blood mononuclear cells (PBMCs). The primary objective of this study was to investigate the role of two signaling pathways, STAT1/6, and two important modulators of immunometabolism, leptin and PPARs, in the development of T2DM with and without CVD. Furthermore, the study aimed to assess the correlation between these factors and the dynamics of CD14 in PBMCs. This research was conducted within the context of a growing body of literature on the complex pathophysiology of T2DM and its association with CVD. Prior studies have indicated that T2DM is characterized by an imbalance in immunometabolism and the involvement of various signaling pathways.

MATERIALS AND METHODS

Blood samples were collected from a total of 47 subjects, including 7 healthy volunteers, 20 individuals diagnosed with diabetes and cardiovascular disease (D.CVD) and another 20 individuals diagnosed with diabetes only (D). PBMCs were isolated from these samples, and the expression levels of leptin, PPARγ, PPARα, and CD14 genes were measured using Real-Time PCR.

RESULTS

The most relevant result showed that diabetic patients with CVD had significantly higher levels of leptin expression, which was positively correlated with STAT1 (r = 0.7497, p = 0.0001). On the other hand, diabetic patients without CVD had elevated PPARγ expression, which was strongly correlated with STAT6 (r = 0.8437, p = 0.0001). Interestingly, we found a significant increase in the PPARγ/ PPARα ratio in the D.CVD group compared to the D group (4.273 ± 0.9531; 7.52 ± 3.556, p = 0.0479). Moreover, CD14 expression was significantly reduced in this group compared to diabetic patients without CVD.

CONCLUSION

These findings suggested that the immunometabolic imbalance in T2DM was driven by a STAT1/Leptin phenotype in diabetic patients with CVD and by a STAT6/PPARγ phenotype in diabetic patients without CVD. Taking into account STAT1/Leptin and STAT6/PPARγ profiling could help clinicians identify novel therapeutic targets for T2DM and other related diseases.

Angiopoietin-like protein 3 deficiency combined with valsartan administration protects better against podocyte damage in streptozotocin-induced diabetic nephropathy mice

Diabetic nephropathy (DN) is a common leading cause of end-stage renal disease (ESRD). Podocyte injury is a major pathogenesis of DN. Pharmacological inhibition of the renin-angiotensin-aldosterone system (RAAS) is insufficient to fully prevent the development of ESRD. The present investigation aims to evaluate the protective function of valsartan, an angiotensin receptor blocker, alone and in combination with angiopoietin-like protein 3 (Angptl3) knockout against renal damage and podocyte injury in streptozotocin (STZ)-induced diabetic mice. The mice were divided into four groups: normal control group, STZ-induced DN group, valsartan + DN group (val, 100 mg/kg, po), and Angptl3-/- + valsartan + DN group. Tests on kidney function, renal pathology, podocyte ultrastructure, podocyte apoptosis, reactive oxygen species (ROS) production, and autophagy were performed. The combined Angptl3 knockout/valsartan treatment significantly attenuated diabetes-induced renal pathological damage and improved podocyte ultrastructure compared with valsartan alone. The combined administration ameliorated glomerular injury by increasing nephrin, podocin, and CD2-associated protein (CD2AP) expression levels and inhibiting podocyte loss by apoptosis. Compared with valsartan alone, Angptl3-/- and valsartan combination therapy significantly improved the renal function, as demonstrated by decreasing levels of serum urea nitrogen, creatinine, and urinary albumin. Additionally, the combination treatment significantly activated autophagy and reduced the ROS production than valsartan alone. These findings highlight the role of valsartan to Angptl3 knockout could have much better outcome that opens the future for drugs that could inhibit Angptl3.

Histone deacetylase 3 inhibitor attenuates diabetic retinopathy in mice

Diabetic retinopathy is one of the most common microvascular complications of diabetes. Inhibition of histone deacetylase 3 (Hdac3) was proven to be a successful way to ameliorate central nervous system injury and vision problem in a glaucoma mouse model. However, its role in diabetic retinopathy remains largely unknown. Eight-week-old C57BL/6J mice were intraperitoneally injected with 50 mg of streptozotocin for 5 consecutive days to induce diabetes. After 1 wk, diabetic mice were selected and treated with Hdac3 inhibitor RGFP966 once every 3 days for 12 consecutive weeks. It was found that RGFP966 could decrease the mRNA and protein expression of Hdac3. It significantly increased diabetic retinopathy-reduced retinal thickness without affecting fasting blood glucose. It also decreased diabetic retinopathy-activated oxidative stress and cell apoptosis. Moreover, diabetic retinopathy mice displayed an increased expression of vascular endothelial growth factor and a decreased expression of glial fibrillary acidic protein, both of which were partially restored by RGFP966 treatment. Mechanically, RGFP966 decreased the expression of NADPH oxidase 2 (Nox2) whereas it increased the expression of superoxide dismutase 2 (Sod2) in diabetic retinopathy mice. In conclusion, RGFP966 significantly reduces oxidative stress, inflammation, and cell apoptosis in the retina of streptozotocin-induced diabetic mice, which may be associated with its modulation of Nox2 and Sod2 expression.NEW & NOTEWORTHY The study demonstrated that RGFP966 significantly reduced oxidative stress, inflammation, and cell apoptosis in the retina of streptozotocin-induced diabetic mice, which may be associated with Nox2 and Sod2 expression.

Effect of Nicotine on STAT1 Pathway and Oxidative Stress in Rat Lungs

Background

Tobacco use is responsible for millions of preventable deaths due to cancer. Nicotine, an alkaloid chemical found in tobacco was proved to cause chronic inflammation and oxidative stress. The transcription factor STAT1 induces the expression of many proinflammatory genes and has been suggested to be a target for anti-inflammatory therapeutics. The following study investigated the effect of Nicotine on STAT1 pathway and oxidative stress in rat lung tissue.

Methods

Thirty rats were divided into 3 groups; group I considered as control, group II; its rats were daily injected with Nicotine at a dose of 0.4 mg/100 gm body for 8 successive weeks and group III; its rats were daily injected with Nicotine as group II, but the injection was stopped for another 4 weeks. STAT1α protein was assessed by immunohistochemistry, COX-2 and iNOS genes expression were evaluated by real time PCR and thiobarbituric acid reactive substances (TBARS) and total thiols were measured using spectrophotometric methods in the lung tissues of the rats.

Results

The results of the study revealed that group II rats had the highest expression of STAT1α protein and COX-2 and iNOS genes and oxidative stress in their lung tissues. Nicotine cessation for 4 weeks caused a marked reduction in the expression of STAT1α protein, COX-2 and iNOS genes and oxidative stress.

Conclusion

Induction of STAT1 pathway and the increase in oxidative stress may be the mechanisms through which Nicotine may induce its harmful effects.

Pharmacological Actions, Molecular Mechanisms, Pharmacokinetic Progressions, and Clinical Applications of Hydroxysafflor Yellow A in Antidiabetic Research

Hydroxysafflor yellow A (HSYA), a nutraceutical compound derived from safflower (Carthamus tinctorius), has been shown as an effective therapeutic agent in cardiovascular diseases, cancer, and diabetes. Our previous study showed that the effect of HSYA on high-glucose-induced podocyte injury is related to its anti-inflammatory activities via macrophage polarization. Based on the information provided on PubMed, Scopus and Wanfang database, we currently aim to provide an updated overview of the role of HSYA in antidiabetic research from the following points: pharmacological actions, molecular mechanisms, pharmacokinetic progressions, and clinical applications. The pharmacokinetic research of HSYA has laid foundations for the clinical applications of HSYA injection in diabetic nephropathy, diabetic retinopathy, and diabetic neuropathy. The application of HSYA as an antidiabetic oral medicament has been investigated based on its recent oral delivery system research. In vivo and in vitro pharmacological research indicated that the antidiabetic activities of HSYA were based mainly on its antioxidant and anti-inflammatory mechanisms via JNK/c-jun pathway, NOX4 pathway, and macrophage differentiation. Further anti-inflammatory exploration related to NF-κB signaling, MAPK pathway, and PI3K/Akt/mTOR pathway might deserve attention in the future. The anti-inflammatory activities of HSYA related to diabetes and diabetic complications will be a highlight in our following research.

Azithromycin inhibited oxidative stress and apoptosis of high glucose-induced podocytes by inhibiting STAT1 pathway

Azithromycin (AZM) has a therapeutic effect on diabetes, but there is no report on whether AZM has a therapeutic effect on diabetic nephropathy (DN) and its specific mechanism. Cell survival was detected by CCK-8. The expression of the inflammatory factors TNF-α, IL-1β, and IL-6 was determined by ELISA. The expression of inflammatory proteins MCP-1, NLPR3, and ASC was detected by western blot. The expression of MDA, LDH, and SOD was detected by the appropriate kit. Apoptosis was detected by flow cytometry and apoptosis-related proteins Bcl-2, Bax, Caspase-3, 6, 9, and Cleaved caspase-3, 6, 9 were detected by western blot. In addition, the expression of STAT1 was detected by western blot. AZM can increase the activity of high glucose-induced podocytes (p < .05). After high glucose induction, the expression of TNF-α, IL-1β, and IL-6 was increased and the expression of MCP-1, NLPR3, and ASC proteins was also increased (p < .001). When AZM was added, the expression of all the above-mentioned proteins was decreased (p < .001). In addition, MDA, LDH, and SOD were increased after high glucose induction, while decreased after AZM treatment (p < .001). AZM can inhibit apoptosis and the expression of Bax and Cleaved caspase-3, 6, 9, and promote the expression of Bcl-2 (p < .001). Furthermore, the expression of STAT1 was increased after high glucose induction, while the expression of STAT1 was decreased after AZM action (p < .01). By adding a STAT1 agonist IFN-γ, the effects of AZM on inflammation, oxidative stress, and apoptosis of high glucose-induced podocytes were inhibited (p < .05). AZM inhibited inflammation, oxidative stress, and apoptosis of high glucose-induced podocytes by inhibiting STAT1 pathway.

Astragaloside IV protects against podocyte apoptosis by inhibiting oxidative stress via activating PPARγ-Klotho-FoxO1 axis in diabetic nephropathy

AIMS

Podocyte apoptosis plays an important role in the pathogenesis of diabetic nephropathy (DN). Astragaloside IV (AS-IV) has been shown to protect against podocyte apoptosis. Here we aim to investigate the mechanism responsible for the protective effects of AS-IV.

MAIN METHODS

Diabetic db/db mice and high glucose (HG)-cultured podocytes were treated with AS-IV. Renal function and histopathological changes were measured to evaluate the therapeutic effects of AS-IV against DN. Adenovirus-mediated Klotho overexpression, Klotho siRNA, and PPARγ inhibitor were applied in vitro to investigate the potential mechanism. The expression levels of mRNA and proteins were analyzed by qRT-PCR, western blot or immunofluorescence. Intracellular ROS and mitochondrial superoxide were detected by DHE and MitoSOx Red, respectively. Cell apoptosis was evaluated by TUNEL staining and flow cytometry.

KEY FINDINGS

AS-IV improved renal function and ameliorated podocyte injury in db/db mice accompanied with enhanced Klotho expression in glomerular podocytes. In vitro, AS-IV inhibited HG-induced podocyte apoptosis and restored HG-inhibited Klotho expression, whereas Klotho knockdown abrogated the anti-apoptosis action of AS-IV. Further study showed that adenovirus-mediated Klotho overexpression enhanced Forkhead transcription factor O1 (FoxO1)-dependent antioxidant activity and attenuated HG-evoked oxidative stress and apoptosis. AS-IV prevented HG-induced FoxO1 inhibition and oxidative stress, whereas Klotho knockdown reversed these effects. Cotreatment with PPARγ inhibitor T0070907 abolished AS-IV-induced Klotho expression and anti-apoptosis action.

SIGNIFICANCE

These data suggested that AS-IV attenuated podocyte apoptosis presumably by inhibiting oxidative stress via activating PPARγ-Klotho-FoxO1 signaling pathway, thereby ameliorating DN. This study provided new insights into the molecular mechanisms of AS-IV against DN.

Renoprotective effect of Stat1 deletion in murine aristolochic acid nephropathy

Injured tubule epithelium stimulates a profibrotic milieu that accelerates loss of function in chronic kidney disease (CKD). This study tested the role of signal transducer and activator of transcription 1 (STAT1) in the progressive loss of kidney function in aristolochic acid (AA) nephropathy, a model of CKD. Mean serum creatinine concentration increased in wild-type (WT) littermates treated with AA, whereas Stat1-/- mice were protected. Focal increases in the apical expression of kidney injury molecule (KIM)-1 were observed in the proximal tubules of WT mice with AA treatment but were absent in Stat1-/- mice in the treatment group as well as in both control groups. A composite injury score, an indicator of proximal tubule injury, was reduced in Stat1-/- mice treated with AA. Increased expression of integrin-β6 and phosphorylated Smad2/3 in proximal tubules as well as interstitial collagen and fibronectin were observed in WT mice following AA treatment but were all decreased in AA-treated Stat1-/- mice. The data indicated that STAT1 activation facilitated the development of progressive kidney injury and interstitial fibrosis in AA nephropathy.

Forsythoside A Alleviates High Glucose-Induced Oxidative Stress and Inflammation in Podocytes by Inactivating MAPK Signaling via MMP12 Inhibition

BACKGROUND

Podocyte injury serves an important role during the progression of diabetic nephropathy (DN). The aim of this study was to investigate the effects of forsythoside A (FA) on high glucose (HG)-induced podocyte injury and to identify the possible mechanisms.

METHODS

MPC-5 podocytes were cultured under HG conditions. After exposure to different doses of FA, cell viability and apoptosis were respectively evaluated with CCK-8 assay and flow cytometry. Then, the levels of oxidative stress-related markers and inflammatory factors were examined by corresponding kits. Western blot analysis was employed to detect the expression of Nox2, Nox4, COX-2, iNOS and matrix metalloproteinases 12 (MMP12). Subsequently, MMP12 was overexpressed to assess whether the effects of FA on HG-stimulated podocyte injury were mediated by MMP12 and MAPK signaling.

RESULTS

Results indicated that FA dose-dependently elevated cell viability, reduced cell apoptosis in HG-induced MPC-5 cells. Additionally, FA significantly inhibited oxidative stress, which could be certified by decreased content of malondialdehyde (MDA), enhanced activities of superoxide dismutase (SOD) and catalase (CAT), and downregulated expression of Nox2 and Nox4. Moreover, notably reduced levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were observed in FA-treated MPC-5 cells under HG conditions, accompanied by decreased COX-2 and iNOS expression. Remarkably, FA suppressed MMP12 expression in a dose-dependent manner, and the effects of FA on MPC-5 cells exposed to HG were partially counteracted by MMP12 overexpression. Mechanically, FA inactivated the expression of phospho-ERK (p-ERK), p-p38 and p-JNK, which was restored after MMP12 overexpression.

CONCLUSION

These findings demonstrate a protective mechanism of FA by inactivating MAPK signaling via MMP12 inhibition in HG-induced podocyte injury, providing a promising therapeutic candidate for the treatment of DN.

Restraint Stress Alters Expression of Glucocorticoid Bioavailability Mediators, Suppresses Nrf2, and Promotes Oxidative Stress in Liver Tissue

Hepatic glutathione synthesis and antioxidant protection are critically important for efficient detoxification processes in response to metabolic challenges. However, this biosynthetic pathway, regulated by nuclear factor (erythroid-derived 2)-like 2 (Nrf2), previously demonstrated paradoxical repression following exposure to glucocorticoid stress hormones in cultured hepatic cells. Therefore, the present study used an in vivo model of sub-acute psychological stress to investigate the relationship between hepatic corticosteroid regulation and antioxidant systems. Male Wistar rats were kept under control conditions or subjected to six hours of restraint stress applied for 1 or 3 days (n = 8 per group) after which the liver was isolated for assays of oxidative/nitrosative status and expression of corticosteroid regulatory and Nrf2-antioxidant response element pathway members. A single stress exposure produced a significant increase in the expression of corticosterone reactivator, 11-beta-hydroxysteroid dehydrogenase 1 (11β-Hsd1), while the 11β-Hsd2 isozyme and corticosteroid-binding globulin were down-regulated following stress, indicative of an elevated availability of active corticosterone. Exposure to restraint significantly decreased hepatic concentrations of total cysteine thiols and the antioxidant reduced glutathione on Day 1 and increased 3-nitrotyrosinated and carbonylated proteins on Day 3, suggestive of oxidative/nitrosative stress in the liver following stress exposure. Conversely, there was a sustained down-regulation of Nrf2 mRNA and protein in addition to significant reductions in downstream glutamate-cysteine ligase catalytic subunit (Gclc), the rate-limiting enzyme in glutathione synthesis, on Day 1 and 3 of stress treatment. Interestingly, other antioxidant genes including superoxide dismutase 1 and 2, and glutathione peroxidase 4 were significantly up-regulated following an episode of restraint stress. In conclusion, the results of the present study indicate that increased expression of 11β-Hsd1, indicative of elevated tissue glucocorticoid concentrations, may impair the Nrf2-dependent antioxidant response.

Dopamine 1 receptor activation protects mouse diabetic podocytes injury via regulating the PKA/NOX-5/p38 MAPK axis

Diabetic nephropathy (DN) is a major microvascular complication of diabetes that can lead to end-stage renal disease. Podocytes constitute the last barrier of glomerular filtration, whose damage are the direct cause of proteinuria. Dopamine receptors are involved in the regulation of diabetes-induced glomerular hyperfiltration, and only dopamine 1 receptor (D1R) can be amplified in cultured mouse podocytes. However, the exact effect of D1R on diabetic podocytes remains unclear. This study aims to investigate the protective role of D1R activation on diabetic podocytes injury in vivo and vitro as well as its potential mechanism. We observed D1R protective effect respectively in streptozotocin (STZ)-induced type 1 diabetes (T1D) mice as well as mouse podocytes (MPC5) cultured in high glucose (HG, 40 mM) medium. It showed that D1R and podocyte-associated proteins (Podocin, CD2AP and Nephrin) expression were significantly decreased both in the T1D mice (fed for 8 and 12 weeks) and HG-cultured MPC5 cells, while the NOX-5 expression increased. In T1D mice, the levels of 24-h urine protein, serum creatinine and urinary 8-OHdG were increased in a time-dependent manner, at the same time, hematoxylin-eosin (HE) staining and electron microscope observed the kidney lesion and podocytes injury. In vitro, HG induced podocytes oxidative stress and apoptosis, which could be inhibited by SKF38393 (a D1R agonist) and N-acetyl-l-cysteine (NAC, a reactive oxygen species scavenger). Furthermore, there was a decreasing Podocin expression and a significant increasing NOX-5 expression in podocytes transfected with D1R-small interfering RNA (siRNA). More importantly, the expression of phospho-CREB (the PKA downstream transcription factor) was decreased and phospho-p38 MAPK was increased in HG-induced podocytes, which can respectively be activated or blocked by SKF38393, 8-Bromo-CAMP (a PKA activator), NAC, and SB20380 (a p38 MAPK inhibitor). In conclusion, D1R activation can protect diabetic podocytes from apoptosis and oxidative damage, in part through the PKA/NOX-5/p38 MAPK pathway.

FoxO1-mediated inhibition of STAT1 alleviates tubulointerstitial fibrosis and tubule apoptosis in diabetic kidney disease

Background

Tubulointerstitial fibrosis (TIF) plays an important role in the progression of diabetic kidney disease (DKD). Forkhead box O1 (FoxO1) is involved in the regulation of metabolism and cell apoptosis, but its function in renal TIF induced by DKD is less well understood.

Methods

Human kidney biopsies with DKD and normal controls were used to detect apoptosis and TIF induced by diabetes. A mouse model with kidney-specific overexpression of Pax2-3aFoxO1 was established to further investigate the functions of FoxO1 in vivo. The in vitro roles of FoxO1 were analyzed in HK-2 cells with 3aFoxO1-knockin (3aFoxO1-KI) or FoxO1-knockdown (FoxO1-KD) via CRISPR/Cas9. Western blot, immunohistochemistry, and chromatin immunoprecipitation were used to explore the underlying mechanisms.

Findings

In this study, DKD patients had increased renal TIF and apoptosis. In vivo study showed that kidney-specific overexpression of Pax2-3aFoxO1 significantly reduced the expression of p-STAT1 with resultant renal functional impairment, retarding renal TIF and apoptosis in diabetic mice. Meanwhile, We observed that FoxO1-KD in HK-2 cells aggravated the expression of p-STAT1, leading to activation of epithelial-to-mesenchymal transition (EMT) and intrinsic apoptotic pathway. Conversely, EMT and apoptosis were significantly attenuated in HK-2 cells with 3aFoxO1-KI under hyperglycemic conditions.

Interpretation

Taken together, these data suggest that the protection role of FoxO1 against renal TIF and apoptosis in DKD is likely in part to target STAT1 signaling, which may be a promising strategy for long-term treatment of DKD.

Fund

This work was supported by grants from the National Natural Science Foundation of China (grant numbers: 81570746 and 81770812).