The role of Src homology 2 containing protein tyrosine phosphatase 2 in vascular smooth muscle cell migration and proliferation

Formyl peptide receptor 1 signaling strength orchestrates the switch from pro-inflammatory to pro-resolving responses: The way to exert its anti-angiogenic and tumor suppressor functions

The well-paced trigger of inflammation resolution following an inflammatory response is crucial for tissue homeostasis and cancer. In gastrointestinal tumors the Formyl peptide receptor 1 (FPR1) stimulates an inflammation resolution response able to restrain cancer angiogenesis and growth. A preceding inflammatory signal is necessary for the induction of the pro-resolving response. However, if FPR1-induced inflammation resolution and tumor suppressor function require an early pro-inflammatory trigger and how this is achieved remains unknown. A ROS-dependent signaling is activated in response to FPR1 activation. In colorectal carcinoma (CRC) cells, we carefully analyzed this signal showing that FPR1 activation by the fMLF peptide induces biphasic ROS production: a first wave, early, mitochondrial (mROS), followed by a second, late, NADPH oxidase (NOX1)-dependent. mROS cause SHP2 phosphatase inactivation restraining its ability to dephosphorylate and inactivate SRC. SRC, in turn, allows the activation of RAS and Rac1 GTPases. RAS activates MAPK signaling, while Rac1 supports NOX1 activation, that causes the second wave of ROS, reinforcing this signaling cycle. Importantly, for the first time, we demonstrate that mROS production precedes and is necessary for pro-inflammatory mediators' release, while NOX1-dependent ROS are only required for pro-resolving mediators' synthesis. Pharmacological and genetic approaches and functional assays show that this signaling cascade is essential for the pro-resolving and anti-angiogenic properties of FPR1 in CRC. In conclusion, we show that FPR1 elicits pro-resolving effects in CRC activating two waves of ROS production characterized by different strength and kinetics, that parallel and are necessary for pro-inflammatory or pro-resolving mediators' production.

Inhibition of Shp2 ameliorates monocrotaline-induced pulmonary arterial hypertension in rats

Background

Src homology 2 containing protein tyrosine phosphatase (PTP) 2 (Shp2) is a typical tyrosine phosphatase interacting with receptor tyrosine kinase to regulate multiple signaling pathways in diverse pathological processes. Here, we will investigate the effect of Shp2 inhibition on pulmonary arterial hypertension (PAH) in a rat model and its potential cellular and molecular mechanisms underlying.

Methods

Monocrotaline (MCT)-induced PAH rat model was used in this study. Phps-1, a highly selective inhibitor for Shp2, was administered from 21 days to 35 days after MCT single-injection. Microcatheter method was applied to detected hemodynamic parameters. Histological methods were used to determine PVR changes in PAH rats. Moreover, cultured pulmonary artery smooth muscle cells (PASMCs) treated by platelet-derived growth factor (PDGF) with or without Phps-1 was used to investigate the potential cellular and molecular mechanisms underlying in vitro.

Results

Inhibition of Shp2 significantly attenuated MCT-induced increases of mean pulmonary arterial pressure (mPAP), right ventricular systolic pressure (RVSP) and right ventricular hypertrophy (RVH) in rats. Shp2 inhibition effectively decreased thickening of pulmonary artery media and cardiomyocyte hypertrophy as well as perivascular and myocardial fibrosis in MCT-treated rats. Moreover, Shp2 inhibition ameliorated muscularization of pulmonary arterioles in MCT-induced PAH rats. Shp2 inhibition significantly reduced platelet-derived growth factor (PDGF)-triggered proliferation and migration of human pulmonary artery smooth muscle cells (PASMCs), which might be attributed to the inactivations of Akt and Stat3 pathways.

Conclusions

Shp2 contributes to the development of PAH in rats, which might be a potential target for the treatment of PAH.

SHP2 inhibitor PHPS1 protects against atherosclerosis by inhibiting smooth muscle cell proliferation

BACKGROUND

Smooth muscle cells play an important role in the development of atherosclerosis. SHP2 is known to regulate the proliferation and migration of smooth muscle cells. The purpose of this study was to determine whether the SHP2 inhibitor PHPS1 has a pro-atherosclerotic or an atheroprotective effect in vivo and in vitro.

METHODS

After exposure to a high-cholesterol diet for 4 weeks, LDL receptor-deficient (Ldlr-/-) mice were exposed to the SHP2 inhibitor PHPS1 or vehicle. Body weight, serum glucose and lipid levels were determined. The size and composition of atherosclerotic plaques were measured by en face analysis, Movat staining and immunohistochemistry. The phosphorylation of SHP2 and related signaling molecules was analyzed by Western blot. Mechanistic analyses were performed in oxLDL-stimulated cultured vascular smooth muscle cells (VSMCs) with or without 10 mM PHPS1 pretreatment. Protein phosphorylation levels were detected by Western blot, and VSMC proliferation was assessed by BrdU staining.

RESULTS

PHPS1 decreased the number of atherosclerotic plaques without significantly affecting body weight, serum glucose levels or lipid metabolism. Plaque composition analysis showed a significant decrease in the number of VSMCs in atherosclerotic lesions of Ldlr-/- mice treated with PHPS1. Stimulation with oxLDL induced a dose-dependent increase in the number of VSMCs and in SHP2 and ERK phosphorylation levels, and these effects were blocked by PHPS1.

CONCLUSION

The SHP2 inhibitor PHPS1 exerts a protective effect against atherosclerosis by reducing VSMC proliferation via SHP2/ERK pathway activation.

The interaction of IGF-1/IGF-1R and hydrogen sulfide on the proliferation of mouse primary vascular smooth muscle cells

Hydrogen sulfide (H₂S) is mostly produced by cystathionine-gamma-lyase (CSE) in vascular system and it inhibits the proliferation of vascular smooth muscle cells (SMCs). Insulin-like growth factor-1 (IGF-1), via its receptor (IGF-1R), exerts multiple physiological and pathophysiological effects on the vasculature, including stimulating SMC proliferation and migration, and inhibiting SMC apoptosis. Since H₂S and IGF-1/IGF-1R have opposite effects on SMC proliferation, it becomes imperative to better understand the interaction of these two signaling mechanisms on SMC proliferation. SMCs isolated from small mesenteric arteries of CSE knockout (KO) and wild-type (WT) mice were used in the present study. The effects of IGF-1 and H₂S on SMC proliferation were evaluated with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and bromodeoxyuridine (BrdU) assays. Protein expression was determined by western blot, and H₂S-induced protein S-sulfhydration was assessed with a modified biotin switch assay. We found that IGF-1 dose-dependently increased the proliferation of both WT-SMCs and KO-SMCs, and this effect was more significant in KO-SMCs. Supplement of sodium hydrosulfide (NaHS) inhibited IGF-1-induced cell proliferation, while this effect was abolished by blocking IGF-1/IGF-1R signaling with picropodophyllin (PPP) or knocking out of the expression of IGF-1R. H₂S significantly down-regulates the expression of IGF-1R, stimulates IGF-1R S-sulfhydration, and attenuates the binding of IGF-1 with IGF-1R. This study provides novel insight on the involvement of IGF-1/IGF-1R in H₂S-inhibited SMC proliferation and suggests H₂S-based innovative treatment strategies for proliferative cardiovascular diseases such as atherosclerosis.

Gene expression profiles and signaling mechanisms in α2B-adrenoceptor-evoked proliferation of vascular smooth muscle cells

BACKGROUND

α2-adrenoceptors are important regulators of vascular tone and blood pressure. Regulation of cell proliferation is a less well investigated consequence of α2-adrenoceptor activation. We have previously shown that α2B-adrenoceptor activation stimulates proliferation of vascular smooth muscle cells (VSMCs). This may be important for blood vessel development and plasticity and for the pathology and therapeutics of cardiovascular disorders. The underlying cellular mechanisms have remained mostly unknown. This study explored pathways of regulation of gene expression and intracellular signaling related to α2B-adrenoceptor-evoked VSMC proliferation.

RESULTS

The cellular mechanisms and signaling pathways of α2B-adrenoceptor-evoked proliferation of VSMCs are complex and include redundancy. Functional enrichment analysis and pathway analysis identified differentially expressed genes associated with α2B-adrenoceptor-regulated VSMC proliferation. They included the upregulated genes Egr1, F3, Ptgs2 and Serpine1 and the downregulated genes Cx3cl1, Cav1, Rhoa, Nppb and Prrx1. The most highly upregulated gene, Lypd8, represents a novel finding in the VSMC context. Inhibitor library screening and kinase activity profiling were applied to identify kinases in the involved signaling pathways. Putative upstream kinases identified by two different screens included PKC, Raf-1, Src, the MAP kinases p38 and JNK and the receptor tyrosine kinases EGFR and HGF/HGFR. As a novel finding, the Src family kinase Lyn was also identified as a putative upstream kinase.

CONCLUSIONS

α2B-adrenoceptors may mediate their pro-proliferative effects in VSMCs by promoting the activity of bFGF and PDGF and the growth factor receptors EGFR, HGFR and VEGFR-1/2. The Src family kinase Lyn was also identified as a putative upstream kinase. Lyn is known to be expressed in VSMCs and has been identified as an important regulator of GPCR trafficking and GPCR effects on cell proliferation. Identified Ser/Thr kinases included several PKC isoforms and the β-adrenoceptor kinases 1 and 2. Cross-talk between the signaling mechanisms involved in α2B-adrenoceptor-evoked VSMC proliferation thus appears to involve PKC activation, subsequent changes in gene expression, transactivation of EGFR, and modulation of kinase activities and growth factor-mediated signaling. While many of the identified individual signals were relatively small in terms of effect size, many of them were validated by combining pathway analysis and our integrated screening approach.

Expression and prognosis value of SHP2 in patients with pancreatic ductal adenocarcinoma

SHP2 is an src homology (SH) 2 domain-containing protein tyrosine phosphatase (PTP). SHP2 implicitly contributes to tumorigenesis, but the role of SHP2 in pancreatic ductal adenocarcinoma is still unknown. The purpose of this study was to evaluate the prognostic significance and associated expression of SHP2 in pancreatic ductal adenocarcinoma (PDAC) patients. We used immunohistochemistry to assess the protein expression levels of SHP2 in 79 PDAC specimens. The correlations between SHP2 expression and various clinicopathological features were evaluated by Pearson's chi-square (χ (2)) test, Fisher's exact test, and Spearman's rank. Univariate and multivariate Cox regression analyses were used to identify correlations between the immunohistochemical data for SHP2 expression and the clinicopathologic characteristics in PDAC. Kaplan-Meier survival analysis was used to demonstrate the relation between overall survival and the expression of SHP2. Immunohistochemistry revealed significantly higher rates of high SHP2 expression in PDAC tissues (55.7 %) versus adjacent non-cancer tissues (10.1 %) (P < 0.05). Expression of SHP2 was only significantly correlated with histological differentiation (P = 0.033) and vital status (P = 0.025). Patients with high SHP2 expression had shorter overall survival times compared to those with low SHP2 expression (P = 0.000). Multivariate Cox regression analysis revealed that SHP2 overexpression was an independent prognostic factor in PDAC (P = 0.012). Our study demonstrated for the first time that higher expression of SHP2 might be involved in the progression of pancreatic ductal adenocarcinoma, suggesting that SHP2 may be a potential prognostic marker and target for therapy.

The tyrosine phosphatase SHP2 regulates Sertoli cell junction complexes

The blood-testis barrier (BTB) is a large junctional complex composed of tight junctions, adherens junctions, and gap junctions between adjacent Sertoli cells in the seminiferous tubules of the testis. Maintenance of the BTB as well as the controlled disruption and reformation of the barrier is essential for spermatogenesis and male fertility. Tyrosine phosphorylation of BTB proteins is known to regulate the integrity of adherens and tight junctions found at the BTB. SHP2 is a nonreceptor protein tyrosine phosphatase (PTP) and a key regulator of growth factor-mediated tyrosine kinase signaling pathways. We found that SHP2 is localized to Sertoli-Sertoli cell junctions in rat testis. The overexpression of a constitutive active SHP2 mutant, SHP2 Q79R, up-regulated the BTB disruptor ERK1/2 via Src kinase in primary rat Sertoli cells in culture. Furthermore, focal adhesion kinase (FAK), which also supports BTB integrity, was found to interact with SHP2 and constitutive activation of SHP2 decreased FAK tyrosine phosphorylation. Expression of the SHP2 Q79R mutant in primary cultured Sertoli cells also resulted in the loss of tight junction and adherens junction integrity that corresponded with the disruption of the actin cytoskeleton and mislocalization of adherens junction and tight junction proteins N-cadherin, β-catenin, and ZO-1 away from the plasma membrane. These results suggest that SHP2 is a key regulator of BTB integrity and Sertoli cell support of spermatogenesis and fertility.