MicroRNA-33 protects against neointimal hyperplasia induced by arterial mechanical stretch in the grafted vein

Aims

Mechanical factors play significant roles in neointimal hyperplasia after vein grafting, but the mechanisms are not fully understood. Here, we investigated the roles of microRNA-33 (miR-33) in neointimal hyperplasia induced by arterial mechanical stretch after vein grafting.

Methods and results

Grafted veins were generated by the 'cuff' technique. Neointimal hyperplasia and cell proliferation was significantly increased, and miR-33 expression was decreased after 1-, 2-, and 4-week grafts. In contrast, the expression of bone morphogenetic protein 3 (BMP3), which is a putative target of miR-33, and the phosphorylation of smad2 and smad5, which are potential downstream targets of BMP3, were increased in the grafted veins. miR-33 mimics/inhibitor and dual luciferase reporter assay confirmed the interaction of miR-33 and BMP3. miR-33 mimics attenuated, while miR-33 inhibitor accelerated, proliferation of venous smooth muscle cells (SMCs). Moreover, recombinant BMP3 increased SMC proliferation and P-smad2 and P-smad5 levels, whereas BMP3-directed siRNAs had the opposite effect. Then, venous SMCs were exposed to a 10%-1.25 Hz cyclic stretch (arterial stretch) by using the FX4000 cyclic stretch loading system in vitro to mimic arterial mechanical conditions. The arterial stretch increased venous SMC proliferation and repressed miR-33 expression, but enhanced BMP3 expression and smad2 and smad5 phosphorylation. Furthermore, perivascular multi-point injection in vivo demonstrated that agomiR-33 not only attenuates BMP3 expression and smad2 and smad5 phosphorylation, but also slows neointimal formation and cell proliferation in grafted veins. These effects of agomiR-33 on grafted veins could be reversed by local injection of BMP3 lentivirus.

Conclusion

The miR-33-BMP3-smad signalling pathway protects against venous SMC proliferation in response to the arterial stretch. miR-33 is a target that attenuates neointimal hyperplasia in grafted vessels and may have potential clinical applications.

SIRT1 and FOXO Mediate Contractile Differentiation of Vascular Smooth Muscle Cells under Cyclic Stretch

BACKGROUND/AIMS

Physiological mechanical stretch in vivo helps to maintain the quiescent contractile differentiation of vascular smooth muscle cells (VSMCs), but the underlying mechanisms are still unclear. Here, we investigated the effects of SIRT1 in VSMC differentiation in response to mechanical cyclic stretch.

METHODS AND RESULTS

Rat VSMCs were subjected to 10%-1.25Hz-cyclic stretch in vitro using a FX-4000T system. The data indicated that the expression of contractile markers, including α-actin, calponin and SM22α, was significantly enhanced in VSMCs that were subjected to cyclic stretch compared to the static controls. The expression of SIRT1 and FOXO3a was increased by the stretch, but the expression of FOXO4 was decreased. Decreasing SIRT1 by siRNA transfection attenuated the stretch-induced expression of contractile VSMC markers and FOXO3a. Furthermore, increasing SIRT1 by either treatment with activator resveratrol or transfection with a plasmid to induce overexpression increased the expression of FOXO3a and contractile markers, and decreased the expression of FOXO4 in VSMCs. Similar trends were observed in VSMCs of SIRT1 (+/-) knockout mice. The overexpression of FOXO3a promoted the expression of contractile markers in VSMCs, while the overexpression of FOXO4 demonstrated the opposite effect.

CONCLUSION

Our results indicated that physiological cyclic stretch promotes the contractile differentiation of VSMCs via the SIRT1/FOXO pathways and thus contributes to maintaining vascular homeostasis.

Neuropeptide Y Stimulates Proliferation and Migration of Vascular Smooth Muscle Cells from Pregnancy Hypertensive Rats via Y1 and Y5 Receptors

The increased proliferation and migration of vascular smooth muscle cells (VSMCs) play important roles in pathophysiological remodeling of arteries during hypertension in pregnancy. However, the mechanisms involved in this process remain unclear. We hypothesized that Neuropeptide Y (NPY), which is a potent mitogenic peptide, participates in modulating proliferation and migration of VSMCs during hypertension in pregnancy. Using pregnant hypertensive rats, induced by intraperitoneal injection of L-nitro-arginine methylester (L-NAME), the plasma concentration of NPY was detected. Open angle, which reflects the non-uniform remodeling with high sensitivity, was used to detect the pathophysiological vascular remodeling in vivo. The results revealed that NPY concentration and artery open angle were both significantly increased in rats with hypertension in pregnant. The underlying mechanism of elevated NPY on vascular remodeling were further analyzed by using cultured VSMCs in vitro. In cultured VSMCs, NPY most effectively stimulated the migration and proliferation of VSMCs at 10^-6 mol/L, similar to the plasma concentration in L-NAME hypertension in pregnant rats. NPY up-regulated the expressions of both Y1 and Y5 receptors, increased the phosphorylations of STAT3 on Tyr705 and Ser727 residues, and induced the expression of c-Fos. The NPY-induced VSMCs proliferation was reduced by Y5 receptor antagonist, and fully blocked by combinations with other antagonist, such as Y2+Y5, Y1+Y5, and Y1+Y2+Y5. In contrast, the NPY-induced VSMC migration was blocked by either Y receptor antagonist or any combination of Y receptor antagonists. These results suggest that the elevated plasma concentration of NPY during hypertension in pregnancy may induce VSMC proliferation mainly via Y5 receptor, which subsequently modulate STAT3 and c-Fos signaling pathways to result in the vascular remodeling. These results also suggest that NPY mainly acts on VSMCs in vitro via Y1, Y5 receptors and in vascular tissues in vivo via Y5 receptor.

Nuclear envelope proteins Nesprin2 and LaminA regulate proliferation and apoptosis of vascular endothelial cells in response to shear stress

The dysfunction of vascular endothelial cells (ECs) influenced by flow shear stress is crucial for vascular remodeling. However, the roles of nuclear envelope (NE) proteins in shear stress-induced EC dysfunction are still unknown. Our results indicated that, compared with normal shear stress (NSS), low shear stress (LowSS) suppressed the expression of two types of NE proteins, Nesprin2 and LaminA, and increased the proliferation and apoptosis of ECs. Targeted small interfering RNA (siRNA) and gene overexpression plasmid transfection revealed that Nesprin2 and LaminA participate in the regulation of EC proliferation and apoptosis. A protein/DNA array was further used to detect the activation of transcription factors in ECs following transfection with target siRNAs and overexpression plasmids. The regulation of AP-2 and TFIID mediated by Nesprin2 and the activation of Stat-1, Stat-3, Stat-5 and Stat-6 by LaminA were verified under shear stress. Furthermore, using Ingenuity Pathway Analysis software and real-time RT-PCR, the effects of Nesprin2 or LaminA on the downstream target genes of AP-2, TFIID, and Stat-1, Stat-3, Stat-5 and Stat-6, respectively, were investigated under LowSS. Our study has revealed that NE proteins are novel mechano-sensitive molecules in ECs. LowSS suppresses the expression of Nesprin2 and LaminA, which may subsequently modulate the activation of important transcription factors and eventually lead to EC dysfunction.

Induction of thoracic aortic remodeling by endothelial-specific deletion of microRNA-21 in mice

MicroRNAs (miRs) are known to have an important role in modulating vascular biology. MiR21 was found to be involved in the pathogenesis of proliferative vascular disease. The role of miR21 in endothelial cells (ECs) has well studied in vitro, but the study in vivo remains to be elucidated. In this study, miR21 endothelial-specific knockout mice were generated by Cre/LoxP system. Compared with wild-type mice, the miR21 deletion in ECs resulted in structural and functional remodeling of aorta significantly, such as diastolic pressure dropping, maximal tension depression, endothelium-dependent relaxation impairment, an increase of opening angles and wall-thickness/inner diameter ratio, and compliance decrease, in the miR21 endothelial-specific knockout mice. Furthermore, the miR21 deletion in ECs induced down-regulation of collagen I, collagen III and elastin mRNA and proteins, as well as up-regulation of Smad7 and down-regulation of Smad2/5 in the aorta of miR21 endothelial-specific knockout mice. CTGF and downstream MMP/TIMP changes were also identified to mediate vascular remodeling. The results showed that miR21 is identified as a critical molecule to modulate vascular remodeling, which will help to understand the role of miR21 in vascular biology and the pathogenesis of vascular diseases.

Involvement of Rab28 in NF-κB nuclear transport in endothelial cells

Our previous proteomic analysis revealed the expression of Rab28 in arteries of rats. However, the function of Rab28 in mammalian cells, and its role in vessels are still unknown. Coarctation of abdominal aorta above left kidney artery in rat was used as hypertensive animal model. FX-4000 cyclic strain loading system was used to mimic the mechanical condition on vascular cells during hypertension in vitro. Immunofluorescence and co-immunoprecipitation (Co-IP) were used to identify distribution and interaction of Rab28 and nuclear factor kappa B (NF-κB). Rab28 expression was significantly increased in carotid arteries of hypertensive rats. High cyclic strain induced Rab28 expression of endothelial cells (ECs) through a paracrine control of vascular smooth muscles cells (VSMCs), which at least partly via angiotensin II (Ang II). Rab28 knockdown decreased proliferation of ECs, while increased apoptosis and migration. Immunofluorescence revealed that Ang II stimulated the co-translocation of Rab28 and NF-κB from cytoplasm into nucleus. Knockdown of Rab28 attenuated NF-κB activation. Co-IP of NF-κB p65 and Rab28 indicated their interaction. Our results revealed that Rab28, as a novel regulator of NF-κB nuclear transport, might participate in the disturbance of EC homeostasis.

Normal shear stress and vascular smooth muscle cells modulate migration of endothelial cells through histone deacetylase 6 activation and tubulin acetylation

Endothelial cells (ECs) line the innermost of the blood vessel wall and are constantly subjected to shear stress imposed by blood flow. ECs were also influenced by the neighboring vascular smooth muscle cells (VSMCs). The bidirectional communication between ECs and VSMCs modulates vascular homeostasis. In this study, the involvement of histone deacetylase 6 (HDAC6) in modulating migration of ECs co-cultured with VSMCs by the normal level of laminar shear stress (NSS) was investigated. ECs was either cultured alone or co-cultured with VSMCs under static conditions or subjected to NSS of 15 dyne/cm2 by using a parallel-plate co-culture flow chamber system. It was demonstrated that both NSS and VSMCs could increase EC migration. The migration level of ECs co-cultured with VSMCs under NSS was not higher than that under the static condition. The process of EC migration regulated by VSMCs and NSS was associated with the increased expression of HDAC6 and low level of acetylated tubulin. The increase in HDAC6 expression was accompanied by a time-dependent decrease in the acetylation of tubulin in ECs co-cultured with VSMCs. Inhibition of the HDAC6 by siRNA or tributyrin, an inhibitor of HDACs, induced a parallel alteration in the migration and the acetylated tubulin of ECs co-cultured with VSMCs. It was observed by immunofluorescence staining that the acetylated tubulin was distributed mostly around the cell nucleus in ECs co-cultured with VSMCs. The results suggest that the NSS may display a protective function on the vascular homeostasis by modulating EC migration to a normal level in a VSMC-dependent manner. This modulation process involves the down-regulation of acetylated tubulin which results from increased HDAC6 activity in ECs.

Cyclic strain modulates migration and proliferation of vascular smooth muscle cells via Rho-GDIalpha, Rac1, and p38 pathway

Cyclic strain is an important inducer of proliferation and migration of vascular smooth muscle cells (VSMCs) which are involved in vascular remodeling during hypertension. However, its mechanism remains to be elucidated. VSMCs of rat aorta were exposed to cyclic strains in vitro with defined parameters, the static, 5%-strain (physiological) and 15%-strain (pathological), at 1.25 Hz for 24 h respectively. Then the possible signaling molecules participated in strain-induced VSMC migration and proliferation were investigated. The results showed that 15%-strain significantly increased VSMC migration and proliferation in comparison with 5%-strain. Expression of Rho GDP dissociation inhibitor alpha (Rho-GDIalpha) was repressed by 15%-strain, but expressions of phospho-Rac1 and phospho-p38 were increased. Expressions of phospho-Akt and phospho-ERK1/2 were similar between the static, 5%-strain and 15%-strain groups. Rho-GDIalpha "knock-down" by target siRNA transfection increased migration and proliferation of VSMCs, and up-regulated phosphorylation of Rac1 and p38 in all groups. Rac1 "knock-down" repressed migration and proliferation of VSMCs, down-regulated phosphorylation of p38, but had no effect on Rho-GDIalpha expression. When siRNAs of Rho-GDIalpha and Rac1 were co-transfected to VSMCs, the expressions of Rho-GDIalpha and phospho-Rac1 were both decreased, and the effects of Rho-GDIalpha "knock-down" were blocked. Rho-GDIalpha "knock-down" promoted while Rac1 "knock-down" postponed the assembly of stress fibers and focal adhesions in static. The results demonstrate that the pathological cyclic strain might induce migration and proliferation of VSMCs via repressing expression of Rho-GDIalpha, which subsequently verified phosphorylations of Rac1 and p38.

Histone deacetylases modulate vascular smooth muscle cell migration induced by cyclic mechanical strain

The migration of vascular smooth muscle cells (VSMCs) is found to participate in vascular remodeling which is pivotal in the pathogenesis of vascular diseases, for instance atherosclerosis and restenosis. However, the underlying mechanisms of how mechanical strain influence VSMC migration remain to be elucidated. Histone deacetylases (HDACs) are involved in chromatin remodeling and modification of both histone and nonhistone transcription regulatory proteins, thus HDACs modulate genes important for complex biological processes. But whether HDACs take part in modulating migration of VSMCs induced by mechanical strain is poorly understood. Here, we showed that cyclic strain of 1 Hz at 10% elongation for 48 h significantly inhibited the migration of cultured VSMCs compared to the static one. The cyclic strain upregulated the levels of acetylased histone H3 and HDAC7 while downregulated the level of HDAC3/4 in VSMCs. Furthermore, the mechanically induced VSMC migration was diminished by treatment with tributyrin, a HDAC inhibitor. We also observed hyperacetylation of histone H3 and reduced expression of HDAC7 upon tributyrin treatment. These results provide convincing evidence that HDACs are involved in the migration of VSMCs induced by mechanical strain through chromatin remodeling. Thus, inhibition of HDAC may be beneficial in preventing the migration of VSMCs in treating proliferative vascular diseases.

Frequency-Dependent Phenotype Modulation of Vascular Smooth Muscle Cells under Cyclic Mechanical Strain

Phenotype transformation of vascular smooth muscle cells (VSMCs) is known to be modulated by mechanical strain. The present study was designed to investigate how different frequencies of mechanical strain affected VSMC phenotype. VSMCs were subjected to the strains of 10% elongation at 0, 0.5, 1 and 2 Hz for 24 h using a Flexercell strain unit. VSMC phenotype was assessed by cell morphology, measurement of two-dimensional cell area, Western blotting for protein and RT-PCR for mRNA expression of differentiation markers. Possible protein kinases involved were evaluated by Western blotting with their specific antibodies. The strains at certain frequencies could induce a contractile morphology in VSMC with almost perpendicular alignment to the strain direction. The strains also regulated protein and mRNA expression of several differentiation markers, as well as the activation of extracellular signal-regulated kinases (ERKs), p38 MAP kinase and protein kinase B (Akt) in a frequency-dependent manner. Furthermore, the inhibition of the p38 pathway could block the frequency-induced phenotype modulation of VSMCs, but not inhibition of ERK or Akt pathways. These results indicate that the frequency of cyclic strain can result in the differentiated phenotype of VSMCs, and it is mediated at least partly by the activation of the p38 pathway.

Coculture with endothelial cells enhances vascular smooth muscle cell adhesion and spreading via activation of β1-integrin and phosphatidylinositol 3-kinase/Akt

The interactions between endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) play significant roles in the homeostasis of the blood vessel during vascular remodeling. Cell adhesion and spreading are an essential process for VSMC migration, survival and proliferation in the events of vascular physiology and pathophysiology. However, effects of ECs on adhesion and spreading of VSMCs have not been characterized yet. Here, the interaction of ECs and VSMCs on adhesion and spreading of VSMCs were investigated by using a coculture system. The results showed that VSMCs cocultured with ECs exhibited a significant increase in the number of adherent and spreading cells, and much more mRNA (twofold, P<0.01) and protein (threefold, P<0.05) expression of beta(1)-integrin comparing to the control, i.e., VSMCs cultured alone. Furthermore, the enhanced functional activity of beta(1)-integrin expression was confirmed by FACS. A beta(1)-integrin blocking antibody (P5D2) could inhibit the EC-induced VSMC adhesion and spreading. It was demonstrated that in correspondence with enhanced cell adhesion, ECs also prompted focal adhesion complex assembly and stress fiber formation of VSMCs. The phosphatidylinositol 3-kinase (PI3K)/Akt pathway was more pronouncedly activated in response to VSMC attachment. Our results for the first time show that coculture with ECs enhances VSMC adhesion and spreading by up-regulating beta(1)-integrin expression and activating the PI3K/Akt pathway, suggesting that the interaction between ECs and VSMCs serves an important role in vascular homeostasis and remodeling.

[Changes in T-lymphocyte subsets of peripheral blood in patients with filarial chyluria]

OBJECTIVE

To study the changes in T-lymphocyte subsets CD4+:CD8+ of peripheral blood in 29 patients with present chyluria(PPC), 29 patients with chyluria history but without chyluria (PNPC) and 38 healthy controls.

METHODS

The determination of CD3+, CD4+ and CD8+ was conducted using test reagents kits.

RESULTS

The percentage of CD3+, CD4+ cell were signfcantly decreased in PPS group than in PNPC and healthy control group, the ratio of CD4+/CD8+ being under 1.0. The T-lymphocyte subsets (CD3+, CD4+, CD8+) and CD4+/CD8+ ratio of both PNPC and healthy control group were all within normal range.

CONCLUSION

The immune function of the patients with filarial chyluria was impaired in terms of the changes in T-lymphocyte subsets.