Role of AMP-activated protein kinase in fibrogenesis

Fibrosis is a common clinical disease that occurs in a variety of organs, and mainly manifests increased connective tissue of organ tissue and decreased parenchymal cells. Continuous progression may lead to organ structural damage, dysfunction and even depletion, seriously threatening human health and life safety. Therefore, in-depth study of the pathogenesis of fibrosis and the development of effective therapeutic drugs are of great importance for the prevention and treatment of fibrosis. Recent studies provide evidence that AMP-activated protein kinase (AMPK) plays an important role in the development of fibrosis. In combination with related literatures, this paper reviews the structure and biological function of AMPK, AMPK in inflammatory response associated with fibrosis, epithelial-mesenchymal transition, extracellular matrix and myofibroblasts, and the therapeutic role of AMPK as a new target in treating fibrosis diseases.     

Telomeres,telomerases and idopathic pulmonary fibrosis

Idopathic pulmonary fibrosis (IPF), with unknown pathogeny, is a interstitial lung disease.The pathological features are diffuse epithelial-cell lesion and excessive extracellular matrix deposition.Many investigators consider alveolar epithelial cells impairment and abnormal activation, fibroblast proliferation and myofibroblast differentiation as causes, resulting in excessive extracellular matrix disorganization of lung.Recently, it is believed that telomeres and telomerases might play a role in regulating the capacity of fibroblast proliferation and aberrant epithelial repair in IPF.The aim of this article is to review the telomeres, telomerases and their relationship with the idopathic pulmonary fibrosis, furthmore, to identify the etiology and pathogenesis of the idopathic pulmonary fibrosis and provide the study measure for establishing an effective treatment.     

Advances in research on mechanism of CCN proteins in prevention and treatment of obesity and non-alcoholic fatty liver

CCN protein family plays a role in regulating the formation and remodeling of extracellular matrix, inflammation regulation, injury repair and so on, which is closely related to the occurrence and development of metabolic diseases. This review focuses on the mechanism of CCN proteins in obesity and non-alcoholic fatty liver. The roles of CCN proteins in the adipocyte activation, the fibrosis and inflammatory response in non-alcoholic fatty liver, and the injury repair against non-alcoholic fatty liver and its complications are introduced, providing new ideas for the study of CCN proteins in metabolic diseases such as obesity and non-alcoholic fatty liver.     

Advances on role of extracellular vesicles in chronic liver diseases

In recent years, extracellular vesicles are found as an important medium for intercellular signal communication in prokaryotic and higher eukaryotic cells for regulating a variety of biological processes. Extracellular vesicles include exosomes, microvesicles and apoptotic bodies, and can be released into extracellular media by almost all types of cells in vivo and in vitro. Extracellular vesicles are released under physiological and pathological conditions, including liver diseases, and have a wide range of effects on the target cells. This review summarizes the progress in understanding the role of extracellular vesicles in chronic liver diseases. Specifically, how extracellular vesicles regulate non-alcoholic steatohepatitis, alcoholic liver disease, viral hepatitis, liver fibrosis and hepatocellular carcinoma is discussed in detail highlighting extracellular vesicles as a promising therapeutic target for chronic liver diseases.     

Cardiac collagen metabolism in murine viral heart diseases

AIM：To investigate the dynamic alteration of cardiac collagen metabolism in mice with acute,chronic myocarditis and dilated cardiomyopathy (DCM).METHODS：BALB/c mice infected with coxsackievirus B3 were used to establish animal models of acute,chronic myocarditis and dilated cardiomyopathy,while uninfected animals were also prepared and served as controls.After verification of models by histopathological methods and echocardiography,serum concentration of aminoterminal propeptide of type Ⅲ procollagen (PIIINP),aminoterminal propeptide of type Ⅰ procollagen (PINP) and carboxyterminal propeptide of type I procollagen (PICP) in each group of mice were detected by enzyme linked immunosorbent assay (ELISA).The expression of matrix metalloproteinase 1 (MMP-1) and its tissue inhibitor (TIMP-1) were determined by Western blotting analysis.The MMP-1 activity was also detected.RESULTS：Marked myocardial fibrosis was observed in all groups of CVB3-infected mice.Reparative fibrosis,promotion of synthesis and degradation of cardiac collagens were presented in heart tissue of acute myocarditis mice.Both reparative and reactive fibrosis,enhanced synthesis and lightened degradation of collagen were present in chronic myocarditis,while reactive fibrosis and excess collagen synthesis were confirmed in DCM.Expression and activity of MMP-1 was progressively decreased.TIMP-1 showed unchanged.The ratio of MMP-1/TIMP-1 was progressively descended.CONCLUSION：Collagen metabolism was special in different phase of viral heart diseases,which may play different roles in the progression and prognosis of these kinds of disease.     

Role of p38 mitogen-activated protein kinase in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is debilitating, often fatal, expensive to treat and common. The intracellular signals following diabetes that lead to diminished contractility, apoptosis, fibrosis and ultimately heart failure are not fully understood but probably involve p38 mitogen-activated protein kinase (p38), one of serine/threonine kinases which, when activated, cause cardiomyocyte contractile dysfunction and death. Pharmacological inhibitors of p38 suppress inflammation and are undergoing clinical trials of rheumatoid arthritis, chronic obstructive pulmonary disease, psoriasis and acute coronary syndrome. In this review, we discuss the mechanisms, circumstances and consequences of p38 activation in DCM. The purpose is to evaluate p38 inhibition as a potential therapy for DCM.     

Mitogen-activated proteins kinases pathway and pathological pain sensitization

Pathological pain or clinical pain is caused by tissue and nerve injuries, and is usually chronic and mainly divided into inflammatory pain and neuropathic pain. Pathological pain is typically characterized by hyperalgesia (increased responsiveness to noxious stimuli) and allodynia (painful responses to normally innocuous stimuli). The mitogen-activated proteins kinases (MAPKs) are a family of evolutionally conserved molecules that play a critical role in cell signaling, consisting of extracellular signal regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK), which play an important role in neural plasticity of pathological pain. Inhibition of MAPKs alleviates inflammatory pain and neuropathic pain in different animal models. It is very important to study the inhibition of MAPKs as a therapeutic approach to treat pathological pain.     

Effects of FGF-21 and Nrf2 on BLM-induced pulmonary fibrosis in mice

AIM:To investigate the effect of fibroblast growth factor-21 (FGF-21) on bleomycin (BLM)-induced inflammatory response and oxidative stress in the lung, and to further explore the molecular mechanism of FGF-21 against pulmonary fibrosis. METHODS:The lung fibrosis model was induced by BLM intratracheal instillation. A total of 40 mice were randomly divided into control group, BLM group, FGF-21 (1, 2 and 5 mg/kg)+BLM groups. Western blot was used to detected the protein expression of collagen I, fibronectin and nuclear factor E2-related factor 2 (Nrf2). The reactive oxygen species (ROS) production was measured by DCFH-DA staining. The levels of inflammatory cytokines were measured by ELISA. The content of malondialdehyde (MDA), the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx), and the content of hydroxyproline (HYP) were detected by commercially available assay kits. RESULTS:Treatment with FGF-21 notably attenuated BLM-induced the expression levels of inflammatory mediators tumor necrosis factor-α, interleukin-1β and interleukin-6 in the lung tissue. In addition, FGF-21 treatment remarkably reduced the generation of ROS and the content of MDA trigged by BLM, accompanied with the enhanced activity of anti-oxidative enzymes SOD and GPx (P<0.05). Furthermore, treatment with FGF-21 obviously reduced the extracellular matrix (ECM) accumulation by suppressing the expression of collagen I and fibronectin induced by BLM, accompanied with the decreases in the levels of TGF-β1 and HYP. Silencing of Nrf2 expression abolished the protective effect of FGF-21. CONCLUSION:FGF-21 relieves BLM-induced pulmonary fibrosis by reducing the inflammatory response, mitigating oxidative damage and decreasing the ECM deposition via Nrf2 activation, thus providing the basis for the therapeutic effect of FGF-21 on the lung fibrosis.     

Progress of P-selectin glycoprotein ligand-1 in kidney diseases

P-selectin glycoprotein ligand-1 (PSGL-1) is an adhesion molecule mainly expressed on the surface of leukocytes and platelets, which plays a vital part in immune recognition, inflammatory response and thrombosis. The prevalence of chronic kidney disease (CKD) is increased gradually and it has been one of major diseases that threaten the world's public health. In addition, its etiology is complicated, and most of the pathogenesis is incompletely understood. Researches show that PSGL-1 participates in the development of kidney diseases in a variety of ways, and its mechanism may involve signaling pathways such as TGF-β1/Smad and PI3K/AKT/GSK-3β, as well as key renal regulators such as connective tissue growth factor and chemokine (C-C motif) ligand 2. This review summarizes the research progress of PSGL-1 in renal fibrosis, lupus nephritis, obesity-related kidney disease and acute kidney injury.     

Activated Toll-like receptors participate in chronic renal tubulointerstitial injury induced by cyclosporine A

AIM: To study the role of innate immunity in the pathogenesis of renal tubulointerstitial injury.METHODS: The model of nephrotoxic nephropathy was induced by chronic cyclosporine A (CsA) administration (15 mg·kg^-1·d^-1 for 4 weeks) in Sprague-Dawley rats. The tubulointerstitial injury, characterized by inflammatory cell infiltration and striped fibrosis, was examined by the methods of immunohistochemistry and trichrome staining. The expression of Toll-like receptors (TLR), TLR ligand heat-shock protein 70 (HSP70)and intrarenal complement elements (C3, C4d and C9) was evaluated in rat kidneys by the methods of in situ hybridization and immunohistochemistry.RESULTS: Compared with the normal rats, the rats exposed to CsA showed impaired renal function, ED-1-positive cell infiltration and striped tubulointerstitial fibrosis (all P<0.01). Concomitantly, CsA treatment up-regulated the expression of TLR2 and TLR4 at mRNA and protein levels in renal tubular cells, accompanied by increased putative TLR ligand (HSP70) and the immunoreactivity of intrarenal complements. These up-regulated innate immunity components were located in the areas of severe tubulinterstitial injury.CONCLUSION: CsA-induced renal tubulointerstitial injury is closely associated with the activation of intrarenal innate immunity.     

PPARs and TLR-NF-κB signaling pathway

Peroxisome proliferator-activated receptors(PPARs) influence Toll-like receptors(TLRs)-nuclear receptor-κB(NF-κB) signaling pathway through diverse mechanisms to negatively regulate TLR-NF-κB signaling-mediated inflammation and immune responses under para-inflammation condition. However, in pathological states, the balance between inhibition and promotion of inflammation, which is regulated by PPARs and TLR-NF-κB signaling pathway, respectively, has been broken down, resulting in inflammatory cascade and eventually causing chronic non-infectious inflammatory diseases, such as atherosclerosis, ulcerative colitis and rheumatoid arthritis. This review mainly focuses on the interaction between PPARs and TLR-NF-κB signaling pathway either in para-inflammatory status or pathological state, which highlights the importance of PPARs in the process of inflammation and immune responses and provides new interfering targets for the treatment of the diseases like coronary atherosclerotic heart disease.     

Effect of pidotimod on renal function and inflammatory response in rat IgA nephropathy model

AIM:To explore the effect of pidotimod on the renal function in IgA nephropathy (IgAN) rat model, and to further study whether this effect is related to the inhibition of inflammatory response. METHODS:The SD rats (n=36) were randomly divided into control group, IgAN model group, IgAN with prednisone treatment group and IgAN with pidotimod treatment group, with 9 rats in each group. The IgAN model was induced by consecutive oral administration of bovine gamma globulin (BGG) for 8 weeks followed by injection of BGG through tail vein for 3 d. After the IgAN model was established, the drug was continuously used for 4 weeks. At the end of the treatment, the urine protein, serum creatinine and blood urea nitrogen were examined by an automated analyzer. IgA deposition in the renal tissues was observed by immunofluorescence staining. The mRNA expression levels of renal fibrosis markers transforming growth factor-β1 (TGF-β1) and fibronectin 1 in the renal tissues were detected by RT-qPCR. The mRNA and protein levels of pro-inflammatory cytokines interleukin-1β (IL-1β) and IL-6 in the renal tissues were determined by RT-qPCR and Western blot, respectively. RESULTS:No significant difference of the body weight was observed in different groups. Compared with control group, the content of urine protein, serum creatinine and blood urea nitrogen were significantly increased (P<0.01), whereas those were reversed by pidotimod treatment. The results of immunofluorescence staining showed that pidotimod inhibited IgA deposition in the IgAN rats. Pitomod treatment inhibited the mRNA expression levels of renal fibrosis markers TGF-β1 and fibronectin 1, and the mRNA and protein levels of pro-inflammatory cytokines IL-1β and IL-6 in the renal tissues of IgAN rats. CONCLUSION:Pidotimod alleviates IgAN progression in rats by inhibition of inflammatory response.     

Effect of alpha-lipoic acid on expression of miR-21/Smad7 and fibrosis in kidney of diabetic rats

AIM: To investigate the protective effect of alpha-lipoic acid (ALA) on the kidney of the rats with diabetes mellitus (DM), and to discuss the mechanism. METHODS: The DM rats were divided into normal control (NC) group, DM group and ALA group. After treated with ALA for 6 weeks, the rats were sacrificed to detect the relevant biochemical parameters, and the pathological changes of the kidney tissues were observed by HE staining and Masson staining. The protein levels of transforming growth factor-β1 (TGF-1), p-Smad2/3, Smad7, collagen I and collagen Ⅲ were determined by Western blot. In addition, the expression of microRNA-21 (miR-21) was detected by RT-qPCR. RESULTS: Compared with NC group, the kidney weight/body weight, blood glucose (BG), total cholesterol, triglyceride and 24-h urine protein were remarkably increased in DM group (P<0.05). The pathological observation of the kidney tissues showed fibrosis changes in DM group. The level of Smad7 was reduced in DM group, while the levels of TGF-β1, p-Smad2/3, collagen I, collagen Ⅲ and miR-21 in the kidney tissues were increased (P<0.05). After treatment with ALA for 6 weeks, all the relevant biochemical parameters were reduced except BG, and the renal fibrosis lesions were obviously alleviated. Compared with DM group, the levels of TGF-1, p-Smad2/3, collagen I, collagen Ⅲ and miR-21 in the kidney tissues were reduced in ALA group, while the level of Smad7 was increased (P<0.05).CONCLUSION: ALA may prevent the development of renal fibrosis in rats through restraining the expression of TGF-β1 and miR-21, increasing the levels of Smad7 protein, and reducing the deposition of extra cellular matrix.     

Expression of TGF-β1 and Smad2/3 in kidney of STZ-induced diabetic nephropathy rats

AIM: To study the role of TGF-β/Smad pathway in the development of renal fibrosis in diabetic nephropathy.METHODS: Rats were induced to diabetic nephropathy by using tail intravenous injection of STZ.The expression of TGF-β₁, Smad2/3 protein and mRNA in kidney were examined at 2, 4, 8 and 16 weeks after STZ induction.CTGF, collagen-Ⅲ, PAI-1 mRNA expression in kidney at 16 weeks of STZ-induced diabetic nephropathy and normal rats were studied by RT-PCR.RESULTS: Weak TGF-β₁, Smad2/3 protein were detected in normal renal tissues while strong TGF-β₁, Smad2/3 staining were observed in renal tissues of diabetic nephropathy (0.057±0.030/0.223±0.040;0.017±0.010/0.153±0.010, respectively, P<0.05).The TGF-β₁, Smad2/3 protein expression were constantly high with the development of diabetic nephropathy and fibrosis (0.153±0.010, 0.122±0.050, 0.141±0.070 and 0.216±0.030 for 2, 4, 8 and 16 weeks, respectively).The TGF-β₁, Smad2 mRNA expression also increased with the development of diabetic nephropathy (2.86, 3.25 fold compared to control, respectively).The expression of TGF-β₁, Smad2, CTGF, collagen-Ⅲ and PAI-1 mRNA were significantly higher in kidney of 16 week diabetic nephropathy rats than that in normal ones (3.92, 2.95, 1.57, 1.95 and 1.97 folds compare to control, respectively, P<0.05).CONCLUSION: The results indicate that TGF-β₁/ Smad2 pathway activity might play an important role in pathophysiological process of diabetic nephropathy.It may be involved in diabetic renal fibrosis through up-regulation of CTGF and PAI-1 to promote extracellular matrix deposition.     

Effect of urokinase and astragalus mongholicus on expression of Snail1 in rats with cyclosporin A induced nephropathy

AIM: To explore the effect of urokinase (u-PA) and astragalus mongholicus(AM) on expression of Snail1 in rats with cyclosporin A (CsA) induced nephropathy. METHODS: Male SD rats were treated with CsA (25 mg·kg-1·d-1) by gavage to induce chronic kidney disease. The rats were randomly divided into 5 groups: control group, CsA group, u-PA group, AM group and combination group. Renal interstitial fibrosis was graded according to Masson staining. The expression of Snail1 was examined by immunohistochemistry and Western blotting. The expression of E-cadherin and FSP1 was also determined by Western blotting. RESULTS: The levels of collagen deposition and the expression of Snail1 and FSP1 in CsA group and treatment groups were significantly increased as compared to control group (P<0.05), but the expression level in the treatment groups was lower than that in CsA group (P<0.05). E-cadherin was decreased in CsA group, while such effects were significantly abrogated in the treatment groups (P<0.05). The best therapeutic efficacy was observed in combination group. CONCLUSION: Snail1 plays an important role in processing renal fibrosis through mediating epithelial-mesenchymal transition. Urokinase and astragalus mongholicus attenuate renal fibrosis in rats with cyclosporin A induced nephropathy, the mechanism may be related to the inhibition of Snail1 expression and the subsequent prevention of tubular epithelial-mesenchymal transition．     

TL1A promotes development of intestinal fibrosis associated with chron?ic experimental colitis by regulating IL-17 and IFN-γ

AIM To explore how tumor recrosis factor ligand-related molecule 1A (TL1A) promotes the development of intestinal fibrosis associated with chronic experimental colitis by regulating interleukin-17 (IL-17) and interferon-γ (IFN-γ). METHODS Aexperimental colitis-associated wild-type (WT) and TL1A (L-Tg) transgenic intestinal fibrosis model was established by dextran sulfate sodium (DSS) induction.The severity of colitis was evaluated by detecting the disease activity index (DAI). HE staining was used to observe the histopathological changes and pathological score of the colitis.Myeloperoxidase (MPO) was measured in each group. The collagen deposition was detected by Masson’s trichrome staining and Sirius red staining. The lamina propria, spleen and mesenteric lymph nodes(MLN) mononuclear cells were isolated and counted, and the levels of IL-17 and IFN-γ weremeasured by ELISA, andthe percentages of CD4⁺IFN-γ⁺T cells and CD4⁺IL-17⁺T cells were analyzed by flow cytometry. RESULTS After drinking DSS water,the body weight of the mice in DSS/Tg group was decreased significantly as compared with WT group(P<0.05). The DAI score, histology score and MPO activity were significantly increased(P<0.05). Thelevels of IL-17 and IFN-γ, LPMC, spleen and MLN were significantly increased. The percentages of CD4⁺IFN-γ⁺T cells and CD4⁺IL-17⁺T cells were significantlyincreased.The thickness and collagen deposition of the colon were increased inTg group. CONCLUSION TL1A promotes the development of intestinal fibrosis associated with chronic experimental colitis by regulating IL-17 and IFN-γ.     

Chronic metabolic acidosis markedly induces proliferation of mesangial cells in rats

AIM: To study the effects of chronic metabolic acidosis on glomerulus, mesangial cells and the production of extracellular matrix. METHODS: Chronic metabolic acidosis was induced by addition of 0.28 mol/L NH4Cl to drinking water for 3, 7, or 14 days in male Wistar rats (n=10). Light microscope combined with computer software (Motic Images Advanced 3.2) was used to determine the effect of chronic acid loading on renal morphologic changes. The expressions of proliferation cell nuclear antigen (PCNA) and p27 in glomeruli were detected by Western blotting or immunohistochemistry. Fibronectin (FN) mRNA was detected by real-time PCR. The proliferation of mesangial cells in vitro was determined by ［3H］-TdR incorporation. The concentration of FN in cultured supernatant was detected by ELISA. RESULTS: On day 1, 3, 7 and 14, the arterial pH and plasma ［HCO3-］ in experimental rats were significantly decreased. There was a significantly increased in the kidney weight and the ratio of kidney to body weigh in experimental rats on day 3, 7 and 14. The glomerular area and cell numbers also increased significantly. Immunoblotting demonstrated decreased p27 expression and increased PCNA expression in isolated glomeruli, and the expression of PCNA increased in a time-dependent manner following the time of chronic metabolic acidosis. Immunohistochemistry showed increased positive PCNA expression mainly localized to mesangial cells. The expression of FN mRNA was significantly elevated in experimental rats on day 7 and 14. In vitro, acid loading induced mesangial cell proliferation and synthesis of FN. CONCLUSION: These results suggest that chronic metabolic acidosis induces mesangial cell proliferation, and its mechanism may be associated with the downregulation of cell cycle kinase inhibitor p27.     

Progress in monocytes/macrophages regulating cardiac fibrosis after myocardial infarction

Myocardial fibrosis is the main pathophysiology following myocardial infarction, which leads to cardiac remodeling and heart failure ultimately. The inflammatory response of monocyte/macrophage recruitment is essential to heart repair after myocardial infarction. However, macrophages in different periods after myocardial infarction are multifaceted, and participate in the process of myocardial fibrosis. This article mainly elucidates the relationship between monocytes/macrophages and cardiac fibrosis after myocardial infarction.     

Role of intestinal myofibroblasts in IBD-associated intestinal fibrosis

Intestinal fibrosis is the complications of inflammatory bowel disease (IBD), intestinal myofibroblast cells are the key to intestinal fibrosis. Intestinal myofibroblasts and its interaction with inflammatory cells play an important role in IBD-related intestinal fibrosis.