Modified low density lipoproteins decrease the activity and expression of lysosomal acid lipase in human endothelial and smooth muscle cells.

Lysosomal acid lipase (LAL), the only lysosomal enzyme involved in the hydrolysis of LDL-cholesteryl esters, is a key regulator of cellular cholesterol and fatty acid homeostasis and its deficiency contributes to the pathophysiology of various diseases. In this study, we questioned whether oxidized or glycated LDL, a common occurrence in atherosclerosis and diabetes, affect the activity and expression of LAL in vascular endothelial cells (EC) and smooth muscle cells (SMC). LAL activity and expression were assayed in cultured human EC and SMC exposed to oxidized LDL (oxLDL), (±)9-hydroxyoctadecadienoic acid-cholesteryl ester (HODE), glycated LDL (gLDL), or native LDL (nLDL) as control, in the presence or absence of LXR or PPAR-gamma agonists. We found that LAL activity and expression were significantly down regulated by oxLDL and HODE in EC, and by gLDL in SMC. The LXR agonist T0901317 reversed the decreased LAL expression in modified LDL- or HODE-exposed EC (P < 0.001) and in gLDL-exposed SMC, whereas PPAR-gamma agonist rosiglitazone induced a low effect only in EC. In conclusion, modified LDL down regulates LAL expression in human EC and SMC by a process involving the LXR signaling pathway. This is the first demonstration that modified LDL modulate LAL expression, in a cell specific manner.

Identification of gene variants in NOS3, ET-1 and RAS that confer risk and protection against microangiopathy in type 2 diabetic obese subjects.

The study aim was to investigate NOS3 VNTR, NOS3 G894T, EDN1 C8002T, ACE I/D, AGT M235T and AGTR1 A1166C in nonobese and obese T2DM patients, and their interaction with the incidence of microangiopathy. T2DM subjects (n=250; 166 nonobese, and 84 obese) were genotyped for the gene variants by PCR/RFLP. The interaction of these polymorphisms with obesity and their contribution to microangiopathy were analyzed by multivariate regression analysis. A higher frequency of NOS3 4a allele was found in obese (P=0.027) vs. nonobese subjects. ACE D (P=0.009) and AGT 235T (P=0.026) alleles were associated with the reduced risk of diabetic nephropathy in nonobese and obese patients, respectively. In obese subjects, NOS3 4a (P=0.011) had a converse effect to NOS3 894T (P=0.043), and EDN1 8002T (P=0.035) on the prevalence of combined microangiopathy (neuropathy/retinopathy/nephropathy) vs. microangiopathy-negative subjects. The study indicates association of RAS variants with obesity and nephropathy, and an opposite effect of NOS3 VNTR and NOS3 G894T on the occurrence of combined microangiopathy.

Inhibition of JAK/STAT signaling pathway prevents high-glucose-induced increase in endothelin-1 synthesis in human endothelial cells.

Emerging evidence demonstrates the involvement of endothelin-1 (ET-1) in the pathophysiology of cardiovascular disorders associated with diabetes mellitus. The molecular mechanisms accountable for the increased production of ET-1 are not completely defined. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway is an essential pathogenic mechanism leading to endothelial cell dysfunction. Our aim has been to investigate the role of JAK/STAT in the regulation of ET-1 synthesis in human endothelial cells (EAhy926 cells line). EAhy926 cells were exposed to normal (5 mM) or high (25 mM) glucose concentrations in the presence/absence of various JAK/STAT inhibitors. Using real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and gene reporter assay, we found that JAK/STAT inhibitors (STAT1 decoy oligodeoxynucleotides, AG490, S3I201, WP1066) significantly diminished the high-glucose-dependent up-regulation of ET-1 mRNA, peptide synthesis, and promoter activity. In silico analysis of the human ET-1 promoter revealed the presence of typical STAT1-gamma-activated sequence (STAT1-GAS) elements. Transient overexpression of STAT1 indicated an up-regulation of ET-1 promoter activity. Chromatin immunoprecipitation demonstrated the physical interaction of STAT1 proteins with the predicted GAS sites. Regulation of ET-1 synthesis by the JAK/STAT pathway thus represents a novel mechanism by which high glucose induces endothelial cell dysfunction in diabetes. Since the JAK/STAT system is an important regulator of the response of endothelial cells to injury, the modulation of this system and the subsequent decrease in ET-1 level may represent a key pharmacological target in diabetes-associated cardiovascular disorders.

Relationship of eNOS gene variants to diseases that have in common an endothelial cell dysfunction.

The endothelial cell (EC) dysfunction is a common characteristic of various pathologies that include atherosclerosis, hypertension, and Fabry's disease. Aware of the role of eNO and ACE in EC dysfunction, we questioned whether polymorphism of eNOS and/or ACE gene may be a common denominator in these pathologies. Patients with CHD (108), HT (109), Fabry's disease (37) and healthy subjects (control, 141) were genotyped for the eNOSG894T by RFLP-PCR technique and for eNOS4b/a, and ACEI/D polymorphisms by PCR amplification. The results of these studies were statistically evaluated. Compared to controls, the frequency of the eNOSG894T (T allele) was higher in CHD (P=0.03) and Fabry (P=0.01), while the eNOS4b/a (a allele) in CHD (P=0.01) and HT patients (P=0.01). The proportion of the ACEI/D was similar in all subjects. In CHD patients at "low risk" of atherogenic factors, the frequency of the T and a alleles of eNOS gene was high (P=0.03 and 0.02, respectively). Carriers of the T allele of eNOSG894T were over-represented (P=0.04) in Fabry subgroup with renal failure. Compared to women, the eNOS894T alleles were more frequent (P=0.03) in men with CHD and HT, whereas ACE I/D in men (P=0.03) with HT. These findings suggest: (i) the frequency of eNOSG894T and/or eNOS4b/a is significantly associated with coronary dysfunction; (ii) eNOS4b/a confers a relatively high risk of hypertension in subjects with atherogenic risk factors; (iii) the frequency of eNOSG894T is high in Fabry hemizygotes with renal complications. Therefore, eNOS gene polymorphism represent a frequent risk factor for vascular abnormalities in CHD, HT and Fabry's disease, afflictions which have in common, the endothelial dysfunction.