Role of activin receptor-like kinase 1 in vascular development and cerebrovascular diseases

Activin receptor-like kinase 1(ALK1)is a transmembrane serine/threonine receptor kinase of the transforming growth factor beta(TGFβ)receptor superfamily.ALK1 is specifically expressed in vascular endothelial cells,and its dynamic changes are closely related to the proliferation of endothelial cells,the recruitment of pericytes to blood vessels,and functional differentiation during embryonic vascular development.The pathophysiology of many cerebrovascular diseases is today understood as a disorder of endothelial cell function and an imbalance in the proportion of vascular cells.Indeed,mutations in ALK1 and its co-receptor endoglin are major genetic risk factors for vascular arteriovenous malformation.Many studies have shown that ALK1 is closely related to the development of cerebral aneurysms,arteriovenous malformations,and cerebral atherosclerosis.In this review,we describe the various roles of ALK1 in the regulation of angiogenesis and in the maintenance of cerebral vascular homeostasis,and we discuss its relationship to functional dysregulation in cerebrovascular diseases.This review should provide new perspectives for basic research on cerebrovascular diseases and offer more effective targets and strategies for clinical diagnosis,treatment,and prevention.

Role of RhoA in platelet-derived growth factor-BB-induced migration of rat hepatic stellate cells

Background Although the migration of hepatic stellate cells （HSCs） is essential for hepatic fibrotic response, the detailed mechanisms involved are poorly understood. The aim of this study was to examine the role of Rho GTPases （especially RhoA） in platelet-derived growth factor （PDGF）-BB-induced migration of HSCs. Methods The migration of primary rat HSCs was evaluated using transwell Boyden chamber, while cytoskeletal changes were visualized by immunofluorescence staining of intracellular actins and vinculin. Quantitative real-time PCR and Western blotting analysis were used to detect the expression of Rho GTPases （RhoA, Racl and Cdc42） within HSCs and their activation was determined by glutathione S-transferase pull-down assay. Finally, the effects of RhoA on PDGF-BB-induced cell migration and cytoskeletal remodeling were analyzed using HSC-T6 cells stably transfected with constitutively active （CA, Q63L） or dominant negative （DN, T19N） RhoA mutants. Data were analyzed using SPSS 16.0 software. Student＇s t test was used to analyze differences between two groups and one-way analysis of variance （ANOVA） was used among multiple groups. Results Rapid cytoskeletal remodeling led to a significant increase in the motility of primary rat HSCs after haptotactic （direct） and chemotactic （indirect） stimulation by PDGF-BB： PDGF-BB caused a dramatic elevation in the levels of both total and active RhoA protein. However, the levels of mRNA for Rho GTPases, including RhoA, Racl and Cdc42, were unaffected. Furthermore, PDGF-BB induced increased formation of stress fibers and focal adhesions in HSC-T6 cells transfected with CA-RhoA, but not in HSC-T6 transfected with DN-RhoA. Surprisingly, both CA- and DN-RhoA-transfected HSC-T6 cells showed decreased migratory potential in the absence or presence of PDGF-BB compared with controls. Conclusions PDGF-BB induced cytoskeletal remodeling in rat HSCs and promoted their migration via regulation of intracellular RhoA. RhoA may be one of the determinants in PDGF-BB-induced HSC miaration.

Inhibitory effects of rapamycin on the different stages of hepatic fibrosis

AIM: To investigate and compare the inhibitory effects of rapamycin in the different stages of liver fibrosis.

Mechanisms responsible for the inhibitory effects of epothilone B on scar formation after spinal cord injury

Scar formation after spinal cord injury is regarded as an obstacle to axonal regeneration and functional recovery.Epothilone B provides moderate microtubule stabilization and is mainly used for anti-tumor therapy.It also reduces scar tissue formation and promotes axonal regeneration after spinal cord injury.The aim of the present study was to investigate the effect and mechanism of the microtubule-stabilizing reagent epothilone B in decreasing fibrotic scarring through its action on pericytes after spinal cord injury.A rat model of spinal cord injury was established via dorsal complete transection at the T10 vertebra.The rats received an intraperitoneal injection of epothilone B（0.75 mg/kg） at 1 and 15 days post-injury in the epothilone B group or normal saline in the vehicle group.Neuron-glial antigen 2,platelet-derived growth factor receptor β,and fibronectin protein expression were dramatically lower in the epothilone B group than in the vehicle group,but β-tubulin protein expression was greater.Glial fibrillary acidic protein at the injury site was not affected by epothilone B treatment.The Basso,Beattie,and Bresnahan locomotor scores were significantly higher in the epothilone B group than in the vehicle group.The results of this study demonstrated that epothilone B reduced the number of pericytes,inhibited extracellular matrix formation,and suppressed scar formation after spinal cord injury.

Silencing ofα-complex protein-2 reverses alcohol-and cytokine-induced fibrogenesis in hepatic stellate cells

Background and aim:a-complex protein-2(aCP2)encoded by the poly(rC)binding protein 2(PCBP2)gene is responsible for the accumulation of type I collagen in fibrotic livers.In this study,we silenced the PCBP2 gene using a small interfering RNA(siRNA)to reverse alcohol-and cytokine-induced profibrogenic effects on hepatic stellate cells(HSCs).Methods:Primary rat HSCs and the HSC-T6 cell line were used as fibrogenic models to mimic the initiation and perpetuation stages of fibrogenesis,respectively.We previously found that a PCBP2 siRNA,which efficiently silences expression of aCP2,reduces the stability of type I collagen mRNA.We investigated the effects of the PCBP2 siRNA on cell proliferation and migration.Expression of type I collagen in HSCs was analyzed by quantitative real-time PCR and western blotting.In addition,we evaluated the effects of the PCBP2 siRNA on apoptosis and the cell cycle.Results:PCBP2 siRNA reversed multiple alcohol-and cytokine-induced profibrogenic effects on primary rat HSCs and HSC-T6 cells.The PCBP2 siRNA also reversed alcohol-and cytokine-induced accumulation of type I collagen as well as cell proliferation and migration.Moreover,the combination of LY2109761,a transforming growth factor-b1 inhibitor,and the PCBP2 siRNA exerted a synergistic inhibitive effect on the accumulation of type I collagen in HSCs.Conclusions:Silencing of PCBP2 using siRNA could be a potential therapeutic strategy for alcoholic liver fibrosis.

Aggravated pulmonary injury after subarachnoid hemorrhage in PDGF-B^ret/ret mice

Background:Recent advances in surgical and neuroprotective strategies could effectively manage the pathophysiological progression of subarachnoid hemorrhage(SAH).However,pulmonary dysfunction frequently occurs in SAH patients with an increased risk of unsatisfactory outcomes.Based on the similar microvascular structures in the blood-air barrier and blood-brain barrier and possible brain-lung crosstalks,we believe that pericytes may be involved in both neurological and pulmonary dysfunction after SAH.Methods:In our experiments,platelet-derived growth factor B(PDGF-B)retention motif knockout(PDGF-Bret/ret)mice and adeno-associated virus PDGF-B were employed to show the involvement of pericyte deficiency and PDGF-B expression.Neurological score,SAH grade,hematoxylin-eosin staining,and PaO2/FiO2 ratio analysis were performed to evaluate the neurological deficits and pulmonary functions in endovascular perforation SAH models at 24 h after surgery,as well as western blotting and immunofluorescence staining for underlying molecular expressions.Results:We found that neonatal PDGF-Bret/ret mice exhibited pulmonary atelectasis 12 h after birth.Further investigation showed a decrease in PaO2/FiO2 and lung-specific surfactant proteins in adult PDGF-Bret/ret mice.These dysfunctions were much worse than those in wild-type mice at 24 h after SAH.PDGF-B overexpression alleviated pulmonary dysfunction after SAH.Conclusions:These results suggested pulmonary dysfunction after SAH and the pivotal role of PDGF-B signaling for the pathophysiological process and future therapeutic targets of pulmonary injury treatment after SAH.Further studies are needed for pathophysiological investigations and translational studies on pulmonary injuries after SAH.