Absence of K-Ras Reduces Proliferation and Migration But Increases Extracellular Matrix Synthesis in Fibroblasts

Patchouli alcohol against renal fibrosis of spontaneously hypertensive rats via Ras/Raf-1/ERK1/2 signalling pathway

OBJECTIVES

The present study was designed to obverse the protection of patchouli alcohol (PA) ameliorates hypertensive nephropathy in spontaneously hypertensive rats (SHR) and reveals potential mechanism.

METHODS

Briefly, the adult spontaneously hypertensive rats (SHR) or Wistar-Kyoto (WKY) rats (half male and half female) were intragastric gavaged or not with PA (80, 40 and 20 mg/kg) for 8 weeks. Body weight, blood pressure (BP), renal weight, renal function and renal morphology were measured. Further, western blotting and immunohistochemical analysis were used to study the underlying mechanism.

KEY FINDINGS

Compared with the WKY group, plasmatic levels of renin, angiotensin II (Ang-II), transforming growth factor beta 1(TGF-β1), plasminogen activator inhibitor-1(PAI-1), creatinine (Cr), blood urea nitrogen (BUN), renal index, mRNA levels of ERK1/2 and α-SMA were significantly increased in SHR. Histology results showed that renal tubular injury and tubulointerstitial fibrosis occurred in SHR. After administration, SBP of captopril group decreased at each week after administration, especially at 3, 5, 6 7 and 8 weeks (P < 0.05 or P < 0.01). There is no significant effect was assessed in the olive oil group. Decreased plasma Cr, Renin, Ang-II, TGF-β1, PAI-1, SCFAs and Renin, TGF-β1, PAI-1 in renal tissues were observed significantly in captopril (P <0.05 or P < 0.01). Plasma BUN, Ang-II, TGF-β1 and PAI-1 in renal tissues decreased in the olive oil group significantly (P <0.05 or P < 0.01). PA (80, 40 and 20 mg/kg) lowered BP and plasmatic levels of Renin, Ang-II, TGF-β1 and PAI-1. Treatment with PA (40, 20 mg/kg) decreased levels of Cr, BUN and suppressed of activation of pro-fibrosis cytokines including TGF-β1 in kidney. There is no ameliorative change in the olive oil group and the captopril group (P > 0.05) while PA treatment alleviated renal tubular injury and produced dramatic collagen fibre area reductions in mesangial membrane, basement membrane, and renal interstitium obviously (P < 0.05 or P < 0.01). Treatment of SHR with PA-inhibited MFB activation and downregulated mRNA of α-SMA. Treatment with PA suppressed excessive production of the extracellular matrix (ECM) via decreasing Col I, III and FN, downregulating mRNA of tissue inhibitor of TIMP-1 along with upregulating mRNA of MMP-9. The expression of Col III and MMP-9 mRNA-reduced in the captopril group (P < 0.05). In addition, the expression of ERK1/2 and pERK1/2 also reduced in the captopril group significantly (P < 0.05 or P < 0.01). Treatment with PA (20 mg/kg) downregulated proteins expression of Raf-1, ERK1/2 and pERK1/2 and mRNA expression of Ras, Raf-1 and ERK1/2.

CONCLUSIONS

Overall, PA restored normal BP, alleviated renal dysfunction and renal fibrosis, possibly by suppressing Ang II and TGF-β1-mediated Ras/Raf-1/ERK1/2 signalling pathway.

CCN2/CTGF promotes liver fibrosis through crosstalk with the Slit2/Robo signaling

Liver fibrosis is the common outcome of many chronic liver diseases, resulting from altered cell-cell and cell-matrix interactions that promote hepatic stellate cell (HSC) activation and excessive matrix production. This study aimed to investigate functions of cellular communication network factor 2 (CCN2)/Connective tissue growth factor (CTGF), an extracellular signaling modulator of the CYR61/CTGF/Nov (CCN) family, in liver fibrosis. Tamoxifen-inducible conditional knockouts in mice and hepatocyte-specific deletion of this gene in rats were generated using the Cre-lox system. These animals were subjected to peri-central hepatocyte damage caused by carbon tetrachloride. Potential crosstalk of this molecule with a new profibrotic pathway mediated by the Slit2 ligand and Roundabout (Robo) receptors was also examined. We found that Ccn2/Ctgf was highly upregulated in periportal hepatocytes during carbon tetrachloride-induced hepatocyte damage, liver fibrosis and cirrhosis in mice and rats. Overexpression of this molecule was observed in human hepatocellular carcinoma (HCC) that were surrounded with fibrotic cords. Deletion of the Ccn2/Ctgf gene significantly reduced expression of fibrosis-related genes including Slit2, a smooth muscle actin (SMA) and Collagen type I during carbon tetrachloride-induced liver fibrosis in mice and rats. In addition, Ccn2/Ctgf and its truncated mutant carrying the first three domains were able to interact with the 7th -9th epidermal growth factor (EGF) repeats and the C-terminal cysteine knot (CT) motif of Slit2 protein in cultured HSC and fibrotic murine livers. Ectopic expression of Ccn2/Ctgf protein upregulated Slit2, promoted HSC activation, and potentiated fibrotic responses following chronic intoxication by carbon tetrachloride. Moreover, Ccn2/Ctgf and Slit2 synergistically enhanced activation of phosphatidylinositol 3-kinase (PI3K) and AKT in primary HSC, whereas soluble Robo1-Fc chimera protein could inhibit these activities. These observations demonstrate conserved cross-species functions of Ccn2/Ctgf protein in rodent livers. This protein can be induced in hepatocytes and contribute to liver fibrosis. Its novel connection with the Slit2/Robo signaling may have therapeutic implications against fibrosis in chronic liver disease.

Dissecting the Involvement of Ras GTPases in Kidney Fibrosis

Many different regulatory mechanisms of renal fibrosis are known to date, and those related to transforming growth factor-β1 (TGF-β1)-induced signaling have been studied in greater depth. However, in recent years, other signaling pathways have been identified, which contribute to the regulation of these pathological processes. Several studies by our team and others have revealed the involvement of small Ras GTPases in the regulation of the cellular processes that occur in renal fibrosis, such as the activation and proliferation of myofibroblasts or the accumulation of extracellular matrix (ECM) proteins. Intracellular signaling mediated by TGF-β1 and Ras GTPases are closely related, and this interaction also occurs during the development of renal fibrosis. In this review, we update the available in vitro and in vivo knowledge on the role of Ras and its main effectors, such as Erk and Akt, in the cellular mechanisms that occur during the regulation of kidney fibrosis (ECM synthesis, accumulation and activation of myofibroblasts, apoptosis and survival of tubular epithelial cells), as well as the therapeutic strategies for targeting the Ras pathway to intervene on the development of renal fibrosis.

Sos1 Modulates Extracellular Matrix Synthesis, Proliferation, and Migration in Fibroblasts

Non-reversible fibrosis is common in various diseases such as chronic renal failure, liver cirrhosis, chronic pancreatitis, pulmonary fibrosis, rheumatoid arthritis and atherosclerosis. Transforming growth factor beta 1 (TGF-β1) is involved in virtually all types of fibrosis. We previously described the involvement of Ras GTPase isoforms in the regulation of TGF-β1-induced fibrosis. The guanine nucleotide exchange factor Son of Sevenless (Sos) is the main Ras activator, but the role of the ubiquitously expressed Sos1 in the development of fibrosis has not been studied. For this purpose, we isolated and cultured Sos1 knock-out (KO) mouse embryonic fibroblasts, the main extracellular matrix proteins (ECM)-producing cells, and we analyzed ECM synthesis, cell proliferation and migration in the absence of Sos1, as well as the role of the main Sos1-Ras effectors, Erk1/2 and Akt, in these processes. The absence of Sos1 increases collagen I expression (through the PI3K-Akt signaling pathway), total collagen proteins, and slightly increases fibronectin expression; Sos1 regulates fibroblast proliferation through both PI3K-Akt and Raf-Erk pathways, and Sos1-PI3K-Akt signaling regulates fibroblast migration. These study shows that Sos1 regulates ECM synthesis and migration (through Ras-PI3K-Akt) and proliferation (through Ras-PI3K-Akt and Ras-Raf-Erk) in fibroblasts, and describe for the first time the role of the Sos1-Ras signaling axis in the regulation of cellular processes involved in the development of fibrosis.

Pregnancy-Induced High Plasma Levels of Soluble Endoglin in Mice Lead to Preeclampsia Symptoms and Placental Abnormalities

Preeclampsia is a pregnancy-specific disease of high prevalence characterized by the onset of hypertension, among other maternal or fetal signs. Its etiopathogenesis remains elusive, but it is widely accepted that abnormal placentation results in the release of soluble factors that cause the clinical manifestations of the disease. An increased level of soluble endoglin (sEng) in plasma has been proposed to be an early diagnostic and prognostic biomarker of this disease. A pathogenic function of sEng involving hypertension has also been reported in several animal models with high levels of plasma sEng not directly dependent on pregnancy. The aim of this work was to study the functional effect of high plasma levels of sEng in the pathophysiology of preeclampsia in a model of pregnant mice, in which the levels of sEng in the maternal blood during pregnancy replicate the conditions of human preeclampsia. Our results show that wild type pregnant mice carrying human sEng-expressing transgenic fetuses (fWT(hsEng⁺)) present high plasma levels of sEng with a timing profile similar to that of human preeclampsia. High plasma levels of human sEng (hsEng) are associated with hypertension, proteinuria, fetal growth restriction, and the release of soluble factors to maternal plasma. In addition, fWT(hsEng⁺) mice also present placental alterations comparable to those caused by the poor remodeling of the spiral arteries characteristic of preeclampsia. In vitro and ex vivo experiments, performed in a human trophoblast cell line and human placental explants, show that sEng interferes with trophoblast invasion and the associated pseudovasculogenesis, a process by which cytotrophoblasts switch from an epithelial to an endothelial phenotype, both events being related to remodeling of the spiral arteries. Our findings provide a novel and useful animal model for future research in preeclampsia and reveal a much more relevant role of sEng in preeclampsia than initially proposed.

Sitagliptin Inhibits Extracellular Matrix Accumulation and Proliferation in Lung Fibroblasts

BACKGROUND Fibroblasts activation-induced fibrosis can cause idiopathic pulmonary fibrosis (IPF). Excessive activation of fibroblasts contributes to poor healing or severe visceral fibrosis and even organ dysfunction. Sitagliptin acts as a dipeptidyl peptidase 4 inhibitor to reduce glucose level in type 2 diabetes, but its role in fibrosis of lung fibroblasts is elusive. We investigated the mechanism of sitagliptin in TGF-ß-activated lung fibroblasts and evaluated the efficacy of sitagliptin in extracellular matrix accumulation and fibroblasts proliferation. MATERIAL AND METHODS By in vitro lung fibroblasts culture, we assessed the expression of lung fibroblasts biomarker (alpha-SMA) and extracellular matrix (Col-1, Col-3, fibronectin) following TGF-ß stimulation and treatment with sitagliptin. Mechanistically, the phosphorylation level of Smad-3 protein in cells was analyzed using Western blotting, and the apoptosis level was assessed by Western blotting and flow cytometry. The degree of proliferation was determined using immunofluorescence and scratch-healing assay. RESULTS We found that treatment with sitagliptin attenuates fibroblasts activation following TGF-ß stimulation. Furthermore, the extracellular matrix was decreased by sitagliptin treatment by suppressing the phosphorylation level of Smad-3 protein. We found that sitagliptin does not affect apoptosis in fibroblasts, but it does affect the degree of proliferation of lung fibroblasts, thus ameliorating fibrosis after TGF-ß stimulation. CONCLUSIONS Sitagliptin inhibits fibrosis in TGF-ß-induced lung fibroblasts activation, which restrains extracellular matrix formation and cell proliferation in fibroblasts. Therefore, sitagliptin appears to have promise as a treatment of fibroproliferative disease caused by activation and proliferation of fibroblasts.

Effect of STOX1 on recurrent spontaneous abortion by regulating trophoblast cell proliferation and migration via the PI3K/AKT signaling pathway

STOX1 is a transcription factor that is implicated in the high prevalence of human gestational diseases. It has been studied in various types of gestational diseases using different molecular and cellular biological technologies. However, the effect and detailed mechanism of storkhead box 1 (STOX1) in recurrent spontaneous abortion (RSA) remain unknown. This study aimed to explore the effect and detailed mechanism of STOX1 in human trophoblast cells. The result showed that downregulation of STOX1 by short hairpin RNA (shRNA) led to a decrease in proliferation and migration in HTR-8/SVneo cells, while it induced the apoptosis of HTR-8/SVneo cells. Moreover, the result showed that trophoblast cells expressed lower levels of pAKT and p85 subunits after treatment with STOX1 shRNA when compared with control. However, overexpression of STOX1 obviously increased the pAKT and p85 protein expressions. Transfection of pcDNA-AKT plasmid increased cell proliferation and migration in HTR-8/SVneo cells while suppressed the apoptosis of HTR-8/SVneo cells. Furthermore, inhibition of the PI3K/Akt pathway by a specific inhibitor promoted cell apoptosis and aggravatedly suppressed cell proliferation and migration of HTR-8/SVneo cells. On the other hand, upregulation of the PI3K/Akt pathway could increase the relative expression level of Bcl-2 and decrease the relative expression levels of Bax and Bim, while inhibition of the PI3K/Akt pathway led to adverse results. Our results demonstrated that inhibition of STOX1 could suppress trophoblast cell proliferation and migration, while promote apoptosis through inhibiting the PI3K/Akt signaling pathway. These findings might provide a new fundamental mechanism for regulating RSA and could be used to prevent and treat RSA in clinic.

Both knock-down and overexpression of Rap2a small GTPase in macrophages result in impairment of NF-κB activity and inflammatory gene expression

Small Ras GTPases are key molecules that regulate a variety of cellular responses in different cell types. Rap1 plays important functions in the regulation of macrophage biology during inflammation triggered by toll-like receptors (TLRs). However, despite sharing a relatively high degree of similarity with Rap1, no studies concerning Rap2 in macrophages and innate immunity have been reported yet. In this work, we show that either way alterations in the levels of Rap2a hampers proper macrophages response to TLR stimulation. Rap2a is activated by LPS in macrophages, and although putative activator TLR-inducible Ras guanine exchange factor RasGEF1b was sufficient to induce, it was not fully required for Rap2a activation. Silencing of Rap2a impaired LPS-induced production of IL-6 cytokine and KC/Cxcl1 chemokine, and also NF-κB activity as measured by reporter gene studies. Surprisingly, overexpression of Rap2a did also lead to marked inhibition of NF-κB activation induced by LPS, Pam3CSK4 and downstream TLR signaling molecules. We also found that Rap2a can inhibit the LPS-induced phosphorylation of the NF-κB subunit p65 at serine 536. Collectively, our data suggest that expression levels of Rap2a in macrophages might be tightly regulated to avoid unbalanced immune response. Our results implicate Rap2a in TLR-mediated responses by contributing to balanced NF-κB activity status in macrophages.

Slit2-Robo2 signaling modulates the fibrogenic activity and migration of hepatic stellate cells

BACKGROUND & AIM

Slit/Robo signaling was originally identified as a repulsive guidance cue in regulating axon branching and neuronal migration. Hepatic stellate cells (HSCs) are the key fibrogenic cells in the liver, which are migratory when activated, and express neural crest markers. The aim of the present study was to investigate the functional significance of Slit/Robo signaling in liver fibrogenesis and in HSCs.

KEY FINDINGS

By transcriptomic analysis it was found that axon guidance signaling pathways were significantly upregulated in both diethylnitrosamine (DEN) and thioacetamide (TAA)-induced experimental liver fibrosis. The up-regulation of the ligand Slit2 and membrane receptor Robo2 genes within this pathway was further validated in TAA-induced fibrotic livers. By immunofluorescence staining, Robo2 was localized in fibrotic septa of fibrotic liver and on the surface of HSCs. By Western blot analysis, recombinant Slit2 (rSlit2) was found to promote fibrogenic protein expression in JS1 cells, an immortalized mouse HSC line, while activating PI3K/Akt signaling pathway. This effect was abrogated by LY294002, a PI3K/Akt pathway inhibitor. In addition, rSlit2 stimulation markedly inhibited JS1 cells migration in transwell migration assays, which was abrogated by small interfering RNA (siRNA) knockdown of Robo2 in the cells.

SIGNIFICANCE

The present study provides evidence that Slit2/Robo2 signaling mediates the pathogenesis of hepatic fibrogenesis and regulates HSCs biology, thus providing potential markers for HSCs, and therapeutic and diagnostic target toward liver fibrosis.

Long-term treatment with chaethomellic acid A reduces glomerulosclerosis and arteriolosclerosis in a rat model of chronic kidney disease

The high prevalence of end-stage renal disease emphasizes the failure to provide therapies to effectively prevent and/or reverse renal fibrosis. Therefore, the aim of this study was to evaluate the effect of long-term treatment with chaethomellic acid A (CAA), which selectively blocks Ha-Ras farnesylation, on renal mass reduction-induced renal fibrosis. Male Wistar rats were sham-operated (SO) or subjected to 5/6 renal mass reduction (RMR). One week after surgery, rats were placed in four experimental groups: SO:SO rats without treatment (n=13); SO+CAA: SO rats treated with CAA (n=13); RMR:RMR rats without treatment (n=14); and RMR+CAA:RMR rats treated with CAA (n=13). CAA was intraperitoneally administered in a dose of 0.23μg/kg three times a week for six months. Renal fibrosis was evaluated by two-dimensional ultrasonography and histopathological analysis. The kidneys of the RMR animals treated with CAA showed a significantly decrease in the medullary echogenicity (p<0.05) compared with the RMR rats that received no treatment. Glomerulosclerosis and arteriolosclerosis scores were significantly lower (p<0.001) in the RMR+CAA group when compared with the RMR group. There were no significant differences in interstitial fibrosis, interstitial inflammation and tubular dilatation scores between the RMR+CAA and RMR groups. These data suggest that CAA can be a potential future drug to attenuate the progression of chronic kidney disease.

Inhibition of Pin1 alleviates myocardial fibrosis and dysfunction in STZ-induced diabetic mice

Therapeutic management of diabetic myocardial fibrosis remains an unsolved clinical problem. Pin1, a peptidyl-prolyl isomerase, impacts diverse cellular processes and plays a pivotal role in regulating cardiac pathophysiology. Here we investigate the potential mechanism of action of Pin1 and its role in diabetes-induced myocardial fibrosis and dysfunction in mice. Cardiac Pin1, transforming growth factor β1 (TGF-β1), α-smooth muscle actin (α-SMA) and extracellular matrix deposits (collagen I and III) are found to be increased in diabetic mice, which are effectively prevented by Pin1 inhibition by juglone. Pin1 inhibition alleviates cardiac fibrosis and dysfunction. In vitro, high glucose increases Pin1 expression with an accompanying increase in phospho-Akt (Ser 473), p-Smad2, p-Smad3, TGF-β1, and α-SMA in cardiac fibroblasts (CFs). These increases are effectively prevented by the inhibition of Pin1 by juglone. Furthermore, Pin1 inhibition inhibits HG-induced CF proliferation and migration. Our results indicate that Pin1 inhibition attenuates cardiac extracellular matrix deposition by regulating the phosphorylation of Akt, TGF-β1/Smads, MMP activities, and α-SMA expression in diabetic mice.