The Role Of Rab28and The Relative Mechanobiology Mechanism On Vascular Remodeling During Hypertension

Cyclic stretch play an important role in vascular remodeling, and abnormallyincreased cyclic stretch is an important inducer for pathogenesis of vascular diseaseduring hypertension. Vascular smooth muscle cells (VSMCs), which is the maincomposition of blood vessels, are exposed to circumferential strain in vivo. Hence, theresearches on functional change of VSMCs under different cyclic stretch willcontribute to better understanding the pathogenesis of vascular remodeling.Our previous serial studies showed that Rab28is a mechanically sensitive molecule,whose expression in the vessels and VSMCs were regulated by shear stress and cyclicstretch. Also, Rab28and the transcription factor NF-κB, FOXO4were co-localizationin ECs, which suggesting that Rab28might help the transport between nuclear andplasma of these molecules. However, the role of Rab28in the vascular remodelinginduced by high cyclic stretch is still unknown.Coarctation of abdominal aorta above kidney artery of rat was used as hypertensiveanimal model, and sham-operated animal as control. We detected the expression anddistribution of Rab28, FOXO4, FOXO1, phospho-FOXO1as well as the differentiation markers, i.e. α-actin, SM22α, calponin in thoracic aorta tissues in vivo. To investigatethe role of abnormally increased cyclic stretch in vascular remodeling duringhypertension, FX-4000cyclic stretch loading system was used to mimic differentmechanical conditions subjected to VSMCs in vitro.5%and15%cyclic stretch mimicphysiological conditions and hypertensive pathological cyclic stretch respectively, and0%as static control. The expression of Rab28, FOXO4, FOXO1, phospho-FOXO1were detected by western blot in VSMCs, and the differentiation and proliferation ofVSMCs were detected by VSMC markers expression and BrdU ELISA respectively. Byusing target siRNA transfection the effect of FOXO1on differentiation andproliferation of VSMCs was further detected.The results showed that:(1) The carotid artery systolic pressure of hypertensive ratwas significantly increased compared with the sham-operated control after abdominalaorta coarctation for2weeks and4weeks respectively.(2) In comparison with thesham control, the expressions of Rab28, FOXO4, FOXO1and phospho-FOXO1weresignificantly increased in thoracic aorta tissues of hypertensive rat, so did theexpressions of differentiation markers.(3) In vitro cell experiments revealed that15%cyclic stretch remarkably increased expressions of FOXO1and phospho-FOXO1inVSMCs compared with0%static group and5%cyclic stretch, while the proliferationwas promoted and differentiation was inhibited in VSMCs respectively. However, therewas no remarkable effect of different cyclic stretch on FOXO4expression in VSMCs.(4) Target siRNA transfection in static decreased the expressions of FOXO1andphospho-FOXO1, while the differentiation and proliferation of VSMCs weredown-regulated.(5) Immunofluorescence analysis revealed that Rab28mainly exists inthe cytoplasm when VSMCs were static cultured in DMED without serum for32hours.Whereas, Rab28mainly presents in the nucleus when VSMCs were refed with serum for8hours after starvation for24hours. This result suggested that the plasm-nucleartranslocation of Rab28in VSMCs induced by stimulation may be related to itsfunctions.The present results indicated that the abnormally increased cyclic stretch maymodulate the proliferation and differentiation of VSMCs via inducing the expression ofRab28, FOXO1and phospho-FOXO1during hypertension. Our finding suggested thatRab28and FOXO1may play significant roles in vascular remodeling induced byincreased cyclic stretch. Our study provides new mechanobiological evidences forrevealing the pathological mechanism of vascular diseases.