PEX5 prevents cardiomyocyte hypertrophy via suppressing the redox-sensitive signaling pathways MAPKs and STAT3

JAK/STAT3 signaling in cardiac fibrosis: a promising therapeutic target

Cardiac fibrosis is a serious health problem because it is a common pathological change in almost all forms of cardiovascular diseases. Cardiac fibrosis is characterized by the transdifferentiation of cardiac fibroblasts (CFs) into cardiac myofibroblasts and the excessive deposition of extracellular matrix (ECM) components produced by activated myofibroblasts, which leads to fibrotic scar formation and subsequent cardiac dysfunction. However, there are currently few effective therapeutic strategies protecting against fibrogenesis. This lack is largely because the molecular mechanisms of cardiac fibrosis remain unclear despite extensive research. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling cascade is an extensively present intracellular signal transduction pathway and can regulate a wide range of biological processes, including cell proliferation, migration, differentiation, apoptosis, and immune response. Various upstream mediators such as cytokines, growth factors and hormones can initiate signal transmission via this pathway and play corresponding regulatory roles. STAT3 is a crucial player of the JAK/STAT pathway and its activation is related to inflammation, malignant tumors and autoimmune illnesses. Recently, the JAK/STAT3 signaling has been in the spotlight for its role in the occurrence and development of cardiac fibrosis and its activation can promote the proliferation and activation of CFs and the production of ECM proteins, thus leading to cardiac fibrosis. In this manuscript, we discuss the structure, transactivation and regulation of the JAK/STAT3 signaling pathway and review recent progress on the role of this pathway in cardiac fibrosis. Moreover, we summarize the current challenges and opportunities of targeting the JAK/STAT3 signaling for the treatment of fibrosis. In summary, the information presented in this article is critical for comprehending the role of the JAK/STAT3 pathway in cardiac fibrosis, and will also contribute to future research aimed at the development of effective anti-fibrotic therapeutic strategies targeting the JAK/STAT3 signaling.

SIRT3 improved peroxisomes-mitochondria interplay and prevented cardiac hypertrophy via preserving PEX5 expression

The present study identified a novel mechanism underlying the protective effect of Sirtuin 3 (SIRT3) against pathological cardiac hypertrophy, beyond its well-accepted role as a deacetylase in mitochondria. SIRT3 modulates the peroxisomes-mitochondria interplay by preserving the expression of peroxisomal biogenesis factor 5 (PEX5), thereby improving mitochondrial function. Downregulation of PEX5 was observed in the hearts of Sirt3^-/- mice and angiotensin II-induced cardiac hypertrophic mice, as well as in cardiomyocytes with SIRT3 silencing. PEX5 knockdown abolished the protective effect of SIRT3 against cardiomyocyte hypertrophy, whereas PEX5 overexpression alleviated the hypertrophic response induced by SIRT3 inhibition. PEX5 was involved in the regulation of SIRT3 in mitochondrial homeostasis, including mitochondrial membrane potential, mitochondrial dynamic balance, mitochondrial morphology and ultrastructure, as well as ATP production. In addition, SIRT3 alleviated peroxisomal abnormalities in hypertrophic cardiomyocytes via PEX5, as implied by improvement of peroxisomal biogenesis and ultrastructure, as well as increase of peroxisomal catalase and repression of oxidative stress. Finally, the role of PEX5 as a key regulator of the peroxisomes-mitochondria interplay was confirmed, since peroxisomal defects caused by PEX5 deficiency led to mitochondrial impairment. Taken together, these observations indicate that SIRT3 could maintain mitochondrial homeostasis by preserving the peroxisomes-mitochondria interplay via PEX5. Our findings provide a new understanding of the role of SIRT3 in mitochondrial regulation via interorganelle communication in cardiomyocytes.

Electroacupuncture Synergistically Inhibits Proinflammatory Cytokine Production and Improves Cognitive Function in Rats with Cognitive Impairment due to Hepatic Encephalopathy through p38MAPK/STAT3 and TLR4/NF-κB Signaling Pathways

Objective

To investigate the effect of electroacupuncture (EA) on cognitive dysfunction in rats with hepatic encephalopathy and its underlying mechanism.

Methods

Fifty Wistar rats were randomly divided into a normal group (n = 10) and model group (n = 40). Rat models of hepatic encephalopathy were established by administration of carbon tetrachloride and thioacetamide for a total of 12 weeks. At the 9th week after modeling, rats with cognitive impairment in the model group were identified by conducting the Morris water maze test, which were then randomly divided into a control group (CCl₄) and treatment groups including EA group (CCl₄ + EA), lactulose group (CCl₄ + Lac), and EA plus lactulose group (CCl₄ + CM), with 9 rats in each group. At the end of the 9th week, rats in CCl₄ + Lac and CCl₄ + CM groups had lactulose gavage at a dose of 10 mL/kg body weight, while normal control and CCl₄ groups had gavage with the same volume of normal saline once a day for 21 days until the end of the experiment. Rats in CCl₄ + EA and CCl₄ + CM groups underwent acupuncture at Baihui (GV[DU]20), Shenting (GV[DU]24), and Zusanli (ST36) acupoints, among which EA at Baihui and Shenting acupoints were given once daily for 30 min lasting for 21 consecutive days. The effect of the treatment was measured by the Morris water maze test for learning and memory ability and magnetic resonance spectroscopy (MRS) for neuronal metabolism in the hippocampus of rats with hepatic encephalopathy. Pathological change in the rat hippocampus was observed by HE staining, while serum ammonia and liver function markers were detected. Western blot and real-time fluorescent quantitative PCR were used to detect the expressions of specific genes and proteins in the brain tissue.

Results

Compared with those in the control group, rats undergoing EA had significantly shortened escape latency and increased number of platform crossing. H&E staining confirmed that EA improved brain tissue necrosis and ameliorated nuclear pyknosis in rats with hepatic encephalopathy. Significantly decreased levels of serum ammonia, alanine aminotransferase (ALT), aspartate transaminase (AST), total bilirubin (TBil), and total bile acid (TBA) were observed in rats undergoing EA, as well as improved levels of total protein (TP) and albumin (ALB). In addition, EA inhibited the brain expressions of TNF-α, IL-1β, IL-6, iNOS, TLR4, MyD88, NF-κB, p38MAPK, phosphorylated (p)-p38MAPK, STAT3, and p-STAT3 genes, as well as protein expressions of TNF-α, IL-6, TLR4, MyD88, NF-κB, p38MAPK, p-p38MAPK, STAT3, and p-STAT3. MRS showed increased Glx/Cr and decreased NAA/Cr, Cho/Cr and mI/Cr in the control group, and EA significantly reversed such changes in Glx/Cr and mI/Cr values.

Conclusion

EA ameliorated the production of excessive proinflammatory cytokines in the hippocampus of rats with cognitive dysfunction secondary to hepatic encephalopathy, which also gave rise to subsequent changes such as reduced blood ammonia level, brain-protective activated astrocytes, and lower degree of brain tissue injury. The p38MAPK/STAT3 and TLR4/MyD88/NF-κB signaling pathways may be involved. EA can also improve the metabolism of NAA and Cho in the rat hippocampus and thereby improve learning and memory abilities.