CTRP1 Attenuates UUO-induced Renal Fibrosis via AMPK/NOX4 Pathway in Mice

Targeting ASK1 by CS17919 alleviates kidney- and liver-related diseases in murine models

BACKGROUND

Apoptosis signal-regulating kinase 1 (ASK1) is a MAP3K kinase in the MAPK signaling pathway activated by stressors and triggers downstream biological effects such as inflammation and apoptosis; therefore, inhibition of ASK1 kinase activity can protect cells from pathological injury. In this study, we designed and synthesized a novel selective ASK1 inhibitor, CS17919, and investigated its pharmacological effects in various animal models of metabolic injury.

METHODS

First, we validated the ability of CS17919 to inhibit ASK1 in vitro and then tested the safety profile of CS17919 in cell lines compared with Selonsertib (GS-4997), a phase III ASK1 inhibitor. We then conducted pharmacokinetic (PK) studies in mice. Finally, we tested the in vivo efficacy of CS17919 in murine models of chronic kidney disease (CKD) and non-alcoholic steatohepatitis (NASH).

RESULTS

Compared to GS-4997, CS17919 demonstrated comparable inhibition of ASK1 in vitro, exhibited lower toxicity, and provided greater protection in palmitic acid-treated LO2 cells. CS17919 also showed pronounced pharmacokinetic properties such as a high plasma concentration. In the unilateral ureteral obstruction model (UUO), CS17919 and GS-4997 preserved kidney function and showed a non-significant tendency to alleviate kidney fibrosis. In the diabetic kidney disease (DKD) model, CS17919 significantly improved serum creatinine and glomerular sclerosis. In the NASH model, the combination of CS17919 and a THRβ agonist (CS27109) was found to significantly improve liver inflammation and substantially reduced liver fibrosis.

CONCLUSIONS

CS17919 showed cell protective, anti-inflammatory, and antifibrotic effects in vitro and in vivo, suggesting its therapeutic potential for metabolic-related kidney and liver diseases.

DKK3 promotes oxidative stress injury and fibrosis in HK-2 cells by activating NOX4 via β-catenin/TCF4 signaling

Oxidative stress and fibrosis may accelerate the progression of chronic kidney disease (CKD). DKK3 is related to regulating renal fibrosis and CKD. However, the molecular mechanism of DKK3 in regulating oxidative stress and fibrosis during CKD development has not been clarified, which deserves to be investigated. Human proximal tubule epithelial cells (HK-2 cells) were treated with H2O2 to establish a cell model of renal fibrosis. The mRNA and protein expressions were analyzed using qRT-PCR and western blot, respectively. Cell viability and apoptosis were evaluated using MTT assay and flow cytometry, respectively. ROS production was estimated using DCFH-DA. The interactions among TCF4, β-catenin and NOX4 were validated using luciferase activity assay, ChIP and Co-IP. Herein, our results revealed that DKK3 was highly expressed in HK-2 cells treated with H2O2. DKK3 depletion increased H2O2-treated HK-2 cell viability and reduced cell apoptosis, oxidative stress, and fibrosis. Mechanically, DKK3 promoted formation of the β-catenin/TCF4 complex, and activated NOX4 transcription. Upregulation of NOX4 or TCF4 weakened the inhibitory effect of DKK3 knockdown on oxidative stress and fibrosis in H2O2-stimulated HK-2 cells. All our results suggested that DKK3 accelerated oxidative stress and fibrosis through promoting β-catenin/TCF4 complex-mediated activation of NOX4 transcription, which could lead to novel molecules and therapeutic targets for CKD.

CTRP13 alleviates palmitic acid-induced inflammation, oxidative stress, apoptosis and endothelial cell dysfunction in HUVECs

C1q/tumor necrosis factor-related protein 13 (CTRP13) has been reported to participate in cardiovascular diseases. However, the role and molecular mechanism of CTRP13 in obesity-induced endothelial cell damage is still unclear. In palmitic acid (PA)-induced human umbilical vein endothelial cells (HUVECs), qRT-PCR and western blot were used to examine CTRP13 expression. CCK-8 and TUNEL assays were adopted to assess cell viability and apoptosis, respectively. ROS level and MDA content were evaluated by their commercial kits and inflammatory cytokines were measured using ELISA. Endothelial cell dysfunction was evaluated by detecting NO production and eNOS expression, and tube formation assay was performed to assess angiogenesis. AMPK pathway-related proteins were detected by western blot. The results showed that CTRP13 was downregulated in PA-induced HUVECs. CTRP13 overexpression reduced PA-induced cell viability loss and oxidative stress in HUVECs. Moreover, CTRP13 overexpression suppressed PA-induced inflammation and apoptosis, improved angiogenesis ability, and alleviated endothelial cell dysfunction in HUVECs. In addition, CTRP13 overexpression activated AMPK pathway and regulated the expressions of downstream NOX1/p38 and KLF2. Furthermore, compound C countervailed the impacts of CTRP13 overexpression on cell viability, oxidative stress, inflammation, apoptosis and endothelial function in PA-induced HUVECs. To sum up, CTRP13 overexpression may alleviate PA-induced endothelial cell damage.

C1q/TNF-Related Proteins 1, 6 and 8 Are Involved in Corneal Epithelial Wound Closure by Targeting Relaxin Receptor RXFP1 In Vitro

Inadequate wound healing of ocular surface injuries can lead to permanent visual impairment. The relaxin ligand-receptor system has been demonstrated to promote corneal wound healing through increased cell migration and modulation of extracellular matrix formation. Recently, C1q/tumor necrosis factor-related protein (CTRP) 8 was identified as a novel interaction partner of relaxin receptor RXFP1. Additional data also suggest a role for CTRP1 and CTRP6 in RXFP1-mediated cAMP signaling. However, the role of CTRP1, CTRP6 and CTRP8 at the ocular surface remains unclear. In this study, we investigated the effects of CTRP1, CTRP6, and CTRP8 on epithelial ocular surface wound closure and their dependence on the RXFP1 receptor pathway. CTRP1, CTRP6, and CTRP8 expression was analyzed by RT-PCR and immunohistochemistry in human tissues and cell lines derived from the ocular surface and lacrimal apparatus. In vitro ocular surface wound modeling was performed using scratch assays. We analyzed the effects of recombinant CTRP1, CTRP6, and CTRP8 on cell proliferation and migration in human corneal and conjunctival epithelial cell lines. Dependence on RXFP1 signaling was established by inhibiting ligand binding to RXFP1 using a specific anti-RXFP1 antibody. We detected the expression of CTRP1, CTRP6, and CTRP8 in human tissue samples of the cornea, conjunctiva, meibomian gland, efferent tear ducts, and lacrimal gland, as well as in human corneal, conjunctival, and meibomian gland epithelial cell lines. Scratch assays revealed a dose-dependent increase in the closure rate of surface defects in human corneal epithelial cells after treatment with CTRP1, CTRP6, and CTRP8, but not in conjunctival epithelial cells. Inhibition of RXFP1 fully attenuated the effect of CTRP8 on the closure rate of surface defects in human corneal epithelial cells, whereas the CTRP1 and CTRP6 effects were not completely suppressed. Conclusions: Our findings demonstrate a novel role for CTRP1, CTRP6, and CTRP8 in corneal epithelial wound closure and suggest an involvement of the relaxin receptor RXFP1 signaling pathway. This could be a first step toward new approaches for pharmacological and therapeutic intervention.

CTRP1: A novel player in cardiovascular and metabolic diseases

Cardiovascular diseases (CVDs) are a series of diseases induced by inflammation and lipid metabolism disorders, among others. Metabolic diseases can cause inflammation and abnormal lipid metabolism. C1q/TNF-related proteins 1 (CTRP1) is a paralog of adiponectin that belongs to the CTRP subfamily. CTRP1 is expressed and secreted in adipocytes, macrophages, cardiomyocytes, and other cells. It promotes lipid and glucose metabolism but has bidirectional effects on the regulation of inflammation. Inflammation can also inversely stimulate CTRP1 production. A vicious circle may exist between the two. This article introduces CTRP1 from the structure, expression, and different roles of CTRP1 in CVDs and metabolic diseases, to summarize the role of CTRP1 pleiotropy. Moreover, the proteins which may interact with CTRP1 are predicted through GeneCards and STRING, speculating their effects, to provide new ideas for the study of CTRP1.

CTRP1 prevents high fat diet-induced obesity and improves glucose homeostasis in obese and STZ-induced diabetic mice

BACKGROUND

C1q/tumor necrosis factor-related protein 1 (CTRP1) is an adipokine secreted by adipose tissue, related to chondrocyte proliferation, inflammation, and glucose homeostasis. However, the therapeutic effects on metabolic disorders and the underlying mechanism were unclear. Here, we investigated the functions and mechanisms of CTRP1 in treating obesity and diabetes.

METHODS

The plasmid containing human CTRP1 was delivered to mice by hydrodynamic injection, which sustained expression of CTRP1 in the liver and high protein level in the blood. High-fat diet (HFD) fed mice and STZ-induced diabetes model were used to study the effects of CTRP1 on obesity, glucose homeostasis, insulin resistance, and hepatic lipid accumulation. The lipid accumulation in liver and adipose tissue, glucose tolerance, insulin sensitivity, food intake, and energy expenditure were detected by H&E staining, Oil-Red O staining, glucose tolerance test, insulin tolerance test, and metabolic cage, respectively. The metabolic-related genes and signal pathways were determined using qPCR and western blotting.

RESULTS

With high blood circulation, CTRP1 prevented obesity, hyperglycemia, insulin resistance, and fatty liver in HFD-fed mice. CTRP1 also improved glucose metabolism and insulin resistance in obese and STZ-induced diabetic mice. The metabolic cage study revealed that CTRP1 reduced food intake and enhanced energy expenditure. The mechanistic study demonstrated that CTRP1 upregulated the protein level of leptin in blood, thermogenic gene expression in brown adipose tissue, and the gene expression responsible for lipolysis and glycolysis in white adipose tissue (WAT). CTRP1 also downregulated the expression of inflammatory genes in WAT. Overexpression of CTRP1 activated AMPK and PI3K/Akt signaling pathways and inhibited ERK signaling pathway.

CONCLUSION

These results demonstrate that CTRP1 could improve glucose homeostasis and prevent HFD-induced obesity and fatty liver through upregulating the energy expenditure and reducing food intake, suggesting CTRP1 may serve as a promising target for treating metabolic diseases.

Suppressive effect erythropoietin on oxidative stress by targeting AMPK/Nox4/ROS pathway in renal ischemia reperfusion injury

OBJECTIVE

To explore the effect of erythropoietin (EPO) on the AMP-activated protein kinase (AMPK)/nicotinamide adenine dinucleotide phosphatase oxidase 4 (NOX4) signaling pathway during renal ischemia reperfusion injury (RIRI) in rats.

METHODS

A rat model of RIRI was established by clamping the left renal pedicle and removing the right kidney. The rats in the sham group did not have their left renal pedicle clamped. Rats with a model of RIRI were randomly divided into RIRI alone (control), erythropoietin treatment (EPO/RIRI), and Compound C treatment (CPC/RIRI) groups. Hematoxylin-eosin (H&E) staining was used to examine pathological kidney damage. Serum creatinine and urea nitrogen levels were measured to evaluate renal function. Western blotting was performed to detect the expression levels of phosphorylated p-AMPK and total AMPK protein in the kidneys. RT-PCR was used to evaluate the mRNA levels of Nox4 and p22 in the kidneys. Oxidative stress-related indices (ROS, CAT, GSH, SOD, and MDA) were also measured.

RESULTS

EPO treatment improved kidney function by preventing kidney damage induced by the RIRI model. Preventing ischemia/reperfusion injury in the RIRI model was correlated with an increased p-AMPK/AMPK ratio and elevated activity of CAT, GSH, and SOD, which ameliorated the expression of NOX4, p22, ROS, and MDA. Moreover, treatment with CPC (an AMPK inhibitor) reduced the effects of EPO in the RIRI model.

CONCLUSION

EPO treatment protected rats against RIRI in the RIRI model by alleviating oxidative stress by triggering the AMPK/NOX4/ROS pathway.

CTRP1 Attenuates Cerebral Ischemia/Reperfusion Injury via the PERK Signaling Pathway

Cerebral ischemic stroke is one of the leading causes of death worldwide. Previous studies have shown that circulating levels of CTRP1 are upregulated in patients with acute ischemic stroke. However, the function of CTRP1 in neurons remains unclear. The purpose of this study was to explore the role of CTRP1 in cerebral ischemia reperfusion injury (CIRI) and to elucidate the underlying mechanism. Middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation (OGD/R) models were used to simulate cerebral ischemic stroke in vivo and in vitro, respectively. CTRP1 overexpression lentivirus and CTRP1 siRNA were used to observe the effect of CTRP1 expression, and the PERK selective activator CCT020312 was used to activate the PERK signaling pathway. We found the decreased expression of CTRP1 in the cortex of MCAO/R-treated rats and OGD/R-treated primary cortical neurons. CTRP1 overexpression attenuated CIRI, accompanied by the reduction of apoptosis and suppression of the PERK signaling pathway. Interference with CTRP1 expression in vitro aggravated apoptotic activity and increased the expression of proteins involved in the PERK signaling pathway. Moreover, activating the PERK signaling pathway abolished the protective effects of CTRP1 on neuron injury induced by CIRI in vivo and in vitro. In conclusion, CTRP1 protects against CIRI by reducing apoptosis and endoplasmic reticulum stress (ERS) through inhibiting the PERK-dependent signaling pathway, suggesting that CTRP1 plays a crucial role in the pathogenesis of CIRI.

Naringin attenuates renal interstitial fibrosis by regulating the TGF-β/Smad signaling pathway and inflammation

Interstitial fibrosis is a typical feature of all progressive renal diseases. The process of fibrosis is frequently coupled with the presence of pro-fibrotic factors and inflammation. Naringin is a dihydroflavone compound that has been previously reported to exhibit anti-fibrotic effects in the liver, where it prevents oxidative damage. In the present study, a rat model of renal interstitial fibrosis and fibrosis cell model were established to evaluate the effects of naringin on inflammatory proteins and fibrosis markers in kidney of rats and NRK-52E cells, and to elucidate the role of the TGF-β/Smad signaling pathway in this mechanism. Compared with those in fibrotic NRK-52E cells that were stimulated by transforming growth factor-β (TGF-β), gene expression levels of α-smooth muscle actin (α-SMA), collagen 1 (COL1A1), collagen 3 (COL3A1), interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α) were all found to be significantly decreased in fibrotic NRK-52E cells following treatment with naringin (50, 100 and 200 ng/ml). Results from the histopathological studies showed that naringin treatment preserved the renal tissue structure and reduced the degree of fibrosis in the kidney tissues of rats that underwent unilateral ureteral obstruction (UUO). In addition, naringin administration reduced the expression of α-SMA, COL1A1, COL3A1, IL-1β, IL-6 and TNF-α in the kidneys of rats following UUO. The current study, using western blot analysis, indicated that naringin also downregulated the activation of Smad2/3 and the expression of Smad4, high-mobility group protein B1, activator protein-1, NF-κB and cyclooxygenase-2 whilst upregulating the expression of Smad7 in fibrotic NRK-52E cells and rats in the UUO group. In conclusion, naringin could antagonize renal interstitial fibrosis by regulating the TGF-β/Smad pathway and the expression of inflammatory factors.