Expression of IL-1beta, IL-1 receptor type I and IL-1 receptor antagonist in human aortic smooth muscle cells: effects of all-trans-retinoic acid

All‑trans retinoic acid reduces endothelin‑1 expression and increases endothelial nitric oxide synthase phosphorylation in rabbits with atherosclerosis

All-trans retinoic acid (ATRA) is a natural derivative of vitamin A that ameliorates atherosclerosis (AS) by regulating inflammatory factors. However, studies concerning the role of retinoic acid in artery endothelial function are rare. Therefore, the present study investigated its role in regulating the production of endothelin‑1 (ET‑1) and nitric oxide (NO) in rabbits with AS. The rabbits were randomly divided into 3 groups: The control group was administered an ordinary diet, while the high fat group and the ATRA drug intervention group were administered a high fat diet. After 12 weeks, the blood lipid levels of rabbits, the morphological structure of the arterial wall, the arterial intimal permeability, the activity of blood endothelial nitric oxide synthase (eNOS) and the level of plasma NO were investigated. Western blot analysis was used to detect the levels of ET‑1, eNOS and eNOS phosphorylation at Ser‑1177 (p‑eNOS), and a radioimmunoassay was performed to detect the level of ET‑1 in the plasma. It was identified that plaque formation was alleviated in the ATRA group compared with the high fat group, as revealed by hematoxylin and eosin and oil red O staining, and a similar trend was reflected in the immunofluorescence results for endothelial permeability. Western blotting demonstrated significantly decreased ET‑1 expression levels in the arterial tissue of rabbits in the ATRA group compared with the high fat group, together with increased p‑eNOS level (P<0.05), however, no difference was observed in the expression of eNOS (P>0.05). The trends observed for ET‑1 and the activity of eNOS in plasma were similar to those for arterial tissue. Therefore, the present study demonstrated that ATRA may regulate the grade of AS by the reduction of ET‑1 secretion and increased NO formation via increased phosphorylation of eNOS. ATRA provides a potential novel method for the treatment of atherosclerosis.

Cloning and functional studies of a splice variant of CYP26B1 expressed in vascular cells

Background

All-trans retinoic acid (atRA) plays an essential role in the regulation of gene expression, cell growth and differentiation and is also important for normal cardiovascular development but may in turn be involved in cardiovascular diseases, i.e. atherosclerosis and restenosis. The cellular atRA levels are under strict control involving several cytochromes P450 isoforms (CYPs). CYP26 may be the most important regulator of atRA catabolism in vascular cells. The present study describes the molecular cloning, characterization and function of atRA-induced expression of a spliced variant of the CYP26B1 gene.

Methodology/Principal Findings

The coding region of the spliced CYP26B1 lacking exon 2 was amplified from cDNA synthesized from atRA-treated human aortic smooth muscle cells and sequenced. Both the spliced variant and full length CYP26B1 was found to be expressed in cultured human endothelial and smooth muscle cells, and in normal and atherosclerotic vessel. atRA induced both variants of CYP26B1 in cultured vascular cells. Furthermore, the levels of spliced mRNA transcript were 4.5 times higher in the atherosclerotic lesion compared to normal arteries and the expression in the lesions was increased 20-fold upon atRA treatment. The spliced CYP26B1 still has the capability to degrade atRA, but at an initial rate one-third that of the corresponding full length enzyme. Transfection of COS-1 and THP-1 cells with the CYP26B1 spliced variant indicated either an increase or a decrease in the catabolism of atRA, probably depending on the expression of other atRA catabolizing enzymes in the cells.

Conclusions/Significance

Vascular cells express the spliced variant of CYP26B1 lacking exon 2 and it is also increased in atherosclerotic lesions. The spliced variant displays a slower and reduced degradation of atRA as compared to the full-length enzyme. Further studies are needed, however, to clarify the substrate specificity and role of the CYP26B1 splice variant in health and disease.

The Fox and the Rabbits-Environmental Variables and Population Genetics (1) Replication Problems in Association Studies and the Untapped Power of GWAS (2) Vitamin A Deficiency, Herpes Simplex Reactivation and Other Causes of Alzheimer's Disease

Classical population genetics shows that varying permutations of genes and risk factors permit or disallow the effects of causative agents, depending on circumstance. For example, genes and environment determine whether a fox kills black or white rabbits on snow or black ash covered islands. Risk promoting effects are different on each island, but obscured by meta-analysis or GWAS data from both islands, unless partitioned by different contributory factors. In Alzheimer's disease, the foxes appear to be herpes, borrelia or chlamydial infection, hypercholesterolemia, hyperhomocysteinaemia, diabetes, cerebral hypoperfusion, oestrogen depletion, or vitamin A deficiency, all of which promote beta-amyloid deposition in animal models—without the aid of gene variants. All relate to risk factors and subsets of susceptibility genes, which condition their effects. All are less prevalent in convents, where nuns appear less susceptible to the ravages of ageing. Antagonism of the antimicrobial properties of beta-amyloid by Abeta autoantibodies in the ageing population, likely generated by antibodies raised to beta-amyloid/pathogen protein homologues, may play a role in this scenario. These agents are treatable by diet and drugs, vitamin supplementation, pathogen detection and elimination, and autoantibody removal, although again, the beneficial effects of individual treatments may be tempered by genes and environment.

Plasma levels of retinoids, carotenoids and tocopherols in patients with mild obstructive sleep apnoea

BACKGROUND AND OBJECTIVE

OSA is associated with increased incidence of cardiovascular diseases. Pathogenic mechanisms of vascular diseases include thickened vascular walls due to the increased number of smooth muscle cells (SMC). Retinoic acid (RA) suppresses the growth of SMC, and reduced retinoid levels are associated with vascular diseases. Oxidant signalling promotes SMC growth, thus antioxidant levels may also influence the development of cardiovascular diseases. The present study tested the hypothesis that plasmas from OSA patients contain altered levels of retinoids, carotenoids and tocopherols.

METHODS

Plasma samples were taken before and after sleep from patients with OSA (mostly mild) without known cardiovascular diseases and from control subjects. Levels of retinoids, carotenoids and tocopherols were measured using sensitive gas chromatograph-mass spectrometry and high pressure liquid chromatography methods and total antioxidant capacity was assessed fluorometrically.

RESULTS

Results showed that plasmas from patients with OSA had significantly lower retinyl palmitate and 9-cis RA compared with control subjects, while levels of retinol, all-trans RA and 13-cis RA were indifferent. All-transbeta-carotene and 9-cisbeta-carotene were also lower in OSA patients. Levels of all-trans RA and 13-cis RA in OSA patients were reduced after sleep compared with before sleep. OSA patients showed significantly higher delta-tocopherol compared with controls. Treatment of cultured human vascular SMC with post-sleep OSA patient plasmas promoted cell growth, but not in controls.

CONCLUSIONS

Mild OSA exhibits altered levels of specific retinoids, carotenoids and tocopherols, which may be markers and/or mediators for the increased susceptibility of patients to vascular diseases.

Upregulation of RGS4 and downregulation of CPI-17 mediate inhibition of colonic muscle contraction by interleukin-1beta

The pro-inflammatory cytokine IL-1beta contributes to the reduced contractile responses of gut smooth muscle observed in both animal colitis models and human inflammatory bowel diseases. However, the mechanisms are not well understood. The effects of IL-1beta on the signaling targets mediating acetylcholine (ACh)-induced initial and sustained contraction were examined using rabbit colonic circular muscle strips and cultured muscle cells. The contraction was assessed through cell length decrease, myosin light chain (MLC(20)) phosphorylation, and activation of PLC-beta and Rho kinase. Expression levels of the signaling targets were determined by Western blot analysis and real-time RT-PCR. Short interfering RNAs (siRNAs) for regulator of G protein signaling 4 (RGS4) were used to silence endogenous RGS4 in muscle strips or cultured muscle cells. IL-1beta treatment of muscle strips inhibited both initial and sustained contraction and MLC(20) phosphorylation in isolated muscle cells. IL-1beta treatment increased RGS4 expression but had no effect on muscarinic receptor binding or Galpha(q) expression. In contrast, IL-1beta decreased the expression and phosphorylation of CPI-17 but had no effect on RhoA expression or ACh-induced Rho kinase activity. Upregulation of RGS4 and downregulation of CPI-17 by IL-1beta in muscle strips were corroborated in cultured muscle cells. Knockdown of RGS4 by siRNA in both muscle strips and cultured muscle cells blocked the inhibitory effect of IL-1beta on initial contraction and PLC-beta activation, whereas overexpression of RGS4 inhibited PLC-beta activation. These data suggest that IL-1beta upregulates RGS4 expression, resulting in the inhibition of initial contraction and downregulation of CPI-17 expression during sustained contraction in colonic smooth muscle.