A mouse model for spatial and temporal expression of HGF in the heart

Delayed recanalization after MCAO ameliorates ischemic stroke by inhibiting apoptosis via HGF/c-Met/STAT3/Bcl-2 pathway in rats

The activation of tyrosine kinase receptor c-Met by hepatocyte growth factor (HGF) showed an anti-apoptotic effect in numerous disease models. This study aimed to investigate the neuroprotective mechanism of the HGF/c-Met axis-mediated anti-apoptosis underlying the delayed recanalization in a rat model of middle cerebral artery occlusion (MCAO). Permanent MCAO model (pMCAO) was induced by intravascular filament insertion. Recanalization was induced by withdrawing the filament at 3 days after MCAO (rMCAO). HGF levels in the blood serum and brain tissue expressions of HGF, c-Met, phosphorylated-STAT3 (p-STAT3), STAT3, Bcl-2, Bax, cleaved caspase-3(CC3) were assessed using ELISA and western blot, respectively. To study the mechanism, HGF small interfering ribonucleic acid (siRNA) and c-Met inhibitor, su11274, were administered intracerebroventricularly (i.c.v.) or intranasally, respectively. The concentration of HGF in the serum was increased significantly after MCAO. Brain expression of HGF was increased after MCAO and peaked at 3 days after recanalization. HGF and c-Met were both co-localized with neurons. Compared to rats received permanent MCAO, delayed recanalization after MCAO decreased the infarction volume, inhibited neuronal apoptosis, and improved neurobehavioral function, increased expressions of p-STAT3 and its downstream Bcl-2. Mechanistic studies indicated that HGF siRNA and su11274 reversed the neuroprotection including anti-apoptotic effects provided by delayed recanalization. In conclusion, the delayed recanalization after MCAO increased the expression of HGF in the brain, and reduced the infarction and neuronal apoptosis after MCAO, partly via the activation of the HGF/c-Met/STAT3/Bcl-2 signaling pathway. The delayed recanalization may serve as a therapeutic alternative for a subset of ischemic stroke patients.

TGFβ1 and HGF regulate CTGF expression in human atrial fibroblasts and are involved in atrial remodelling in patients with rheumatic heart disease

OBJECTIVE

This study aimed to investigate the effects of transforming growth factor β1 (TGF β1) and hepatocyte growth factor (HGF) on the expression of connective tissue growth factor (CTGF) in human atrial fibroblasts, and to explore the relationship of these factors in atrial fibrosis and atrial anatomical remodelling (AAR) of patients with atrial fibrillation (AF).

METHODS

Fresh right auricular appendix tissue of 20 patients with rheumatic heart disease undergoing valve replacement surgery was collected during surgeries, 10 patients had sinus rhythm(SR), and 10 patients had chronic atrial fibrillation (CAF). Atrial fibroblasts were then cultured from the tissues with differential attachment technique and treated with either TGFβ1 (10 ng/mL) or HGF (100 ng/mL). CTGF mRNA levels were measured by RT-PCR, and CTGF protein content was determined using immunofluorescence and Western blotting assays.

RESULTS

CAF group had higher left atrial diameters (LADs) and higher CTGF mRNA expression in atrial fibroblasts compared with SR group. The CTGF protein content in CAF group was higher than that of SR group and positively correlated with LAD and AF duration. After CAF group was treated with TGFβ1, CTGF mRNA and protein expression were significantly down-regulated, whereas when treated with HGF, expression was up-regulated compared with SR group.

CONCLUSIONS

Increased CTGF expression was associated with enlarged LAD, atrial fibrosis and AAR in patients with AF. TGFβ1 and HGF regulate CTGF expression in human atrial fibroblasts with up-regulation of mRNA and down-regulation of protein, therefore, either promote or inhibit atrial fibrosis, which could be related to the incidence and persistence of AF.

Hepatocyte growth factor plays a particular role in progression of overall cardiac damage in experimental pulmonary hypertension

Background: HGF/MET pathway may have a role in pulmonary hypertension (PH). However, the link between the pathway and development of target organ damage in PH remains elusive. We aimed to demonstrate the relation between plasma HGF and HGF/MET tissue expressions in affected organs during PH progression. Methods: 12 weeks old male Wistar rats were injected with monocrotaline (MCT, 60 mg/kg, s.c.) to induce PH and sacrificed after 1, 2 and 4 weeks. Controls received saline. mRNA levels of HGF regulatory complex (Hgf, Met, Hgfa, Hai-1, Hai-2) were determined in right and left ventricles (RV, LV), lungs, pulmonary artery and liver by RT-qPCR. HGF protein levels in plasma were analysed by ELISA. Results: PH development was associated with a progressive elevation of HGF plasma levels that correlated with relative RV mass. Furthermore, Hgf mRNA expressions at week 4 were upregulated solely in the cardiac ventricles while being downregulated in a. pulmonalis, lungs and liver. Met and Hai-1/Hai-2 followed a similar pattern and were upregulated in cardiac ventricles, where Hgfa remained unchanged, but downregulated in lungs. Conclusion: We suggest that cardiac overexpression of Hgf might contribute to increased plasma HGF in MCT-induced PH. HGF could be exploited as a cardiospecific biomarker and HGF/MET pathway as a target in drug discovery for PH.

Cellular and molecular mechanisms of HGF/Met in the cardiovascular system

Met tyrosine kinase receptor, also known as c-Met, is the HGF (hepatocyte growth factor) receptor. The HGF/Met pathway has a prominent role in cardiovascular remodelling after tissue injury. The present review provides a synopsis of the cellular and molecular mechanisms underlying the effects of HGF/Met in the heart and blood vessels. In vivo, HGF/Met function is particularly important for the protection of the heart in response to both acute and chronic insults, including ischaemic injury and doxorubicin-induced cardiotoxicity. Accordingly, conditional deletion of Met in cardiomyocytes results in impaired organ defence against oxidative stress. After ischaemic injury, activation of Met provides strong anti-apoptotic stimuli for cardiomyocytes through PI3K (phosphoinositide 3-kinase)/Akt and MAPK (mitogen-activated protein kinase) cascades. Recently, we found that HGF/Met is also important for autophagy regulation in cardiomyocytes via the mTOR (mammalian target of rapamycin) pathway. HGF/Met induces proliferation and migration of endothelial cells through Rac1 (Ras-related C3 botulinum toxin substrate 1) activation. In fibroblasts, HGF/Met antagonizes the actions of TGFβ1 (transforming growth factor β1) and AngII (angiotensin II), thus preventing fibrosis. Moreover, HGF/Met influences the inflammatory response of macrophages and the immune response of dendritic cells, indicating its protective function against atherosclerotic and autoimmune diseases. The HGF/Met axis also plays an important role in regulating self-renewal and myocardial regeneration through the enhancement of cardiac progenitor cells. HGF/Met has beneficial effects against myocardial infarction and endothelial dysfunction: the cellular and molecular mechanisms underlying repair function in the heart and blood vessels are common and include pro-angiogenic, anti-inflammatory and anti-fibrotic actions. Thus administration of HGF or HGF mimetics may represent a promising therapeutic agent for the treatment of both coronary and peripheral artery disease.

HGF/Met Axis in Heart Function and Cardioprotection

Hepatocyte growth factor (HGF) and its tyrosine kinase receptor (Met) play important roles in myocardial function both in physiological and pathological situations. In the developing heart, HGF influences cardiomyocyte proliferation and differentiation. In the adult, HGF/Met signaling controls heart homeostasis and prevents oxidative stress in normal cardiomyocytes. Thus, the possible cardiotoxicity of current Met-targeted anti-cancer therapies has to be taken in consideration. In the injured heart, HGF plays important roles in cardioprotection by promoting: (1) prosurvival (anti-apoptotic and anti-autophagic) effects in cardiomyocytes, (2) angiogenesis, (3) inhibition of fibrosis, (4) anti-inflammatory and immunomodulatory signals, and (5) regeneration through activation of cardiac stem cells. Furthermore, we discuss the putative role of elevated HGF as prognostic marker of severity in patients with cardiac diseases. Finally, we examine the potential of HGF-based molecules as new therapeutic tools for the treatment of cardiac diseases.

Agonist antibodies activating the Met receptor protect cardiomyoblasts from cobalt chloride-induced apoptosis and autophagy

Met, the tyrosine kinase receptor for hepatocyte growth factor (HGF), mainly activates prosurvival pathways, including protection from apoptosis. In this work, we investigated the cardioprotective mechanisms of Met activation by agonist monoclonal antibodies (mAbs). Cobalt chloride (CoCl₂), a chemical mimetic of hypoxia, was used to induce cardiac damage in H9c2 cardiomyoblasts, which resulted in reduction of cell viability by (i) caspase-dependent apoptosis and (ii) – surprisingly – autophagy. Blocking either apoptosis with the caspase inhibitor benzyloxycarbonyl-VAD-fluoromethylketone or autophagosome formation with 3-methyladenine prevented loss of cell viability, which suggests that both processes contribute to cardiomyoblast injury. Concomitant treatment with Met-activating antibodies or HGF prevented apoptosis and autophagy. Pro-autophagic Redd1, Bnip3 and phospho-AMPK proteins, which are known to promote autophagy through inactivation of the mTOR pathway, were induced by CoCl₂. Mechanistically, Met agonist antibodies or HGF prevented the inhibition of mTOR and reduced the flux of autophagosome formation. Accordingly, their anti-autophagic function was completely blunted by Temsirolimus, a specific mTOR inhibitor. Targeted Met activation was successful also in the setting of low oxygen conditions, in which Met agonist antibodies or HGF demonstrated anti-apoptotic and anti-autophagic effects. Activation of the Met pathway is thus a promising novel therapeutic tool for ischaemic injury.