Angiotensin II stimulates phosphorylation of 4E-binding protein 1 and p70 S6 kinase in cultured vascular smooth muscle cells.

AIM: To examine the regulatory effects of angiotensin II (Ang II) on the phosphorylation of 4E-binding protein 1 (4E-BP1) and p70 S6 kinase in cultured vascular smooth muscle cells (VSMC), and the contribution of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB) signaling pathway in this process. METHODS: VSMC obtained from rat thoracic aortas were cultured. The phosphorylation of 4E-BP1 and p70 S6 kinase was detected by immunoblotting. RESULTS: Ang II significantly increased the phosphorylation of 4E-BP1 and p70 S6 kinase, with the peaks occurring at, respectively, 10 min and 30 min, after stimulation with Ang II. The stimulatory effect of Ang II on 4E-BP1 and p70 S6 kinase phosphorylation was abrogated by Ang II type 1 receptor (A(T1) receptor) antagonist losartan, and suppressed by PI3K inhibitor LY294002 in a concentration-dependent manner. CONCLUSION: Ang II treatment of VSMC induces the phosphorylation of 4E-BP1 and p70 S6 kinase via A(T1) receptor, and PI3K signaling pathway is involved in this process.

Persistence of MHC DR nonexpression on swine cells by introduction of a mutated MHC class II transactivator gene: a comparison with the effect induced by antisense RNA.

CIITA (class II transactivator) is a coactivator essential for transcription of MHC class II genes. In this study, a construct with a mutated CIITA gene with N-terminal domains depleted was constructed. This mutated CIITA (mCIITA) was able to repress DR and DQ expression in 45.0-60.0% of the mCIITA-transfected clones of swine endothelial cell line PIEC and in B cell line L23, as well as in human cell lines HeLa and Raji. Similarly, 30.0-46.7% of swine cell clones containing the human CIITA antisense RNA also failed to express DR molecules. However, the persistence of the DR repression on the cell lines is quite different. Transfection with mCIITA was persistent for at least 120 days, while with the CIITA antisense RNA, persistence existed for only 35-45 days. To explore the underlying mechanism, Raji cells were transfected with pUHD10-3-mCIITA, a mCIITA-containing, doxycycline-dependent plasmid. The intensity of DR repression is correlated quite well with the efficiencies of the mCIITA expression within the cells in a doxycycline dose-dependent manner. This implicates a competition between the mCIITA and its endogenous full-length counterpart. In addition, we were able to show that purified human CD4 T cells did not respond to the mCIITA-transfected PIECs in xenogeneic mixed lymphocyte endothelial reaction (MLER). The stimulating indices (SI) were only 1.0-1.5, compared with 15.2-18.2 for those transfected with empty vector or an initiation codon-depleted mCIITA that is dysfunctional for protein translation. The results we obtained, especially those for persistent suppression of class II genes, show promise for the possible development of mCIITA-transgenic swine for organ/tissue xenotransplantation.

[The relationship between insulin resistance and postprandial abnormal serum triglyceride metabolism in essential hypertension].

OBJECTIVE: To investigate the relationship between insulin resistance (IR) and postprandial abnormal metabolism of serum triglyceride-rich lipoprotein in essential hypertension (EH). METHODS: In 44 patients with EH and 22 normal subjects (NS). Total cholesterol, HDL cholesterol, LDL cholesterol, apoliprotein AI and apoliprotein B in fasting serum and serum triglyceride before and 2, 4, 6, 8 hours after a standardized fat loading were measured. Triglyceride peak response (TGPR) and the area under triglyceride curve (TG-AUC) over 8 hours were taken as the index of abnormal TG metabolism. Standardized 75 g oral glucose tolerance test was carried, the area under insulin curve (IS-AUC) over 3 hours and insulin sensitivity index were taken as the index of insulin sensitivity. RESULTS: TGPR and TG-AUC were higher in EH than those in NS (TGRP: 4.14 mmol/L +/- 3.0 mmol/L vs 2.06 mmol/L +/- 1.32 mmol/L, P < 0.01; TG-AUC: 20 mmol/L +/- 6 mmol/L vs 10 mmol/L +/- 4 mmol/L, P < 0.05). 65.9% of EH had postprandial abnormal serum triglyceride metabolism. IS-AUC was higher in EH than that in NS, and ISI was lower in EH than that in NS. The incidence of IR in EH was 61%. 44 EH were categorized into 2 groups according to insulin sensitivity: EH with IR (n = 27) and EH with normal insulin sensitivity (NIS, n = 17). TGPR and TG-AUC in EH with IR were significantly higher than those in EH with NIS (TGPR: 5.25 mmol/L +/- 3.03 mmol/L vs 3.16 mmol/L +/- 1.46 mmol/L, P < 0.05; TG-AUC: 25 +/- 13 mmol/L vs 13 +/- 7 mmol/L, P < 0.01). No significant difference was found between EH with NIS and NS (P > 0.05). TG-AUC and TRPG was positively related to IS-AUC and negatively related to ISI. CONCLUSION: Patients with EH had postprandial abnormal serum triglyceride metabolism, insulin resistance may aggravate postprandial triglyceride metabolism in EH.