Effects of glutamine induced heat shock protein 70 overexpression on atrial fibrosis and connexin 43 remodeling in isoprenaline-treated rats / 中华心血管病杂志

<p><b>OBJECTIVE</b>To explore the effects of glutamine (Gln) induced heat shock protein 70(Hsp70) overexpression on atrial fibrosis and connexin 43 remodeling in isoprenaline(ISO)treated rats and related mechanisms.</p><p><b>METHODS</b>Forty male SD rats were randomly divided into five groups (n = 8 each group): control group, DMSO group, ISO 5 mg×kg(-1)×d(-1) group (Fibrosis group), ISO 5 mg×kg(-1)×d(-1) + Ala-Gln 0.75 mg×kg(-1)×d(-1) group (Intervention group) and ISO 5 mg×kg(-1)×d(-1) + QUE 100 mg× kg(-1)×d(-1) + Ala-Gln 0.75 mg×kg(-1)×d(-1) + DMSO group (QUE group).Rats were killed after 7 d. The AngII expression in myocardial tissue was detected by radioimmunoassay; myocardial fibrosis was observed by HE staining.Collagen volume fractions were quantified by Masson staining and as the indicators of atrial fibrosis. The expressions of Hsp70, p-JNK1/2/3, c-Jun and Cx43 were determined with immunohistochemical method.</p><p><b>RESULTS</b>AngII content was similar between the control group [(68.51 ± 10.76) pg/L] and DMSO [(71.47 ± 11.49) pg/L] group (P > 0.05), and significantly increased in fibrosis group [(211.25 ± 49.49) pg/L], intervention group [(185.32 ± 54.85) pg/L] and QUE [(189.90 ± 42.12) pg/L] group (P < 0.01 vs. control group). Atrial fibrosis was significantly higher in the fibrosis group [(29.485 ± 9.966)%] and QUE group [(25.060 ± 8.581)%] but not in the intervention group [(7.861 ± 1.867)%] compared to control group [(6.842 ± 1.674)%] and DMSO group [(7.108 ± 1.343)%]. The expression of Hsp70 was similar among the control group (0.160 ± 0.023), DMSO group (0.163 ± 0.022), fibrosis group (0.166 ± 0.028) and QUE (0.168 ± 0.027) group (P > 0.05) while significantly upregulated in the intervention group (0.215 ± 0.018) (P < 0.01 vs. control group). The expressions of p-JNK1/2/3 and c-Jun were similar between control group (0.151 ± 0.016;0.163 ± 0.022) and DMSO group (0.154 ± 0.021;0.164 ± 0.024)(P > 0.05), while significantly upregulated in fibrosis group (0.202 ± 0.025; 0.254 ± 0.044) and QUE group (0.196 ± 0.024; 0.251 ± 0.027) (P < 0.01 vs. control group) but not in intervention group (0.160 ± 0.025; 0.168 ± 0.024)were not changed obviously (P > 0.05 vs. control group). The content of Cx43 was similar between control group and DMSO group (0.231 ± 0.035 vs. 0.220 ± 0.032, P > 0.05), and was linearly distributed in intercalated disc of the cardiomyocytes, however, the content of Cx43 was significantly reduced (P < 0.01) and the Cx43 distribution was disordered in fibrosis group (0.163 ± 0.013) and QUE group (0.165 ± 0.024), while these changes were not found in intervention group.</p><p><b>CONCLUSION</b>Glutamine could reduce the atrial fibrosis and Cx43 remodeling in isoprenaline-treated rats by up-regulating Hsp70 and inhibiting JNK signaling pathway activation through down-regulating p-JNK1/2/3 and c-Jun expression.</p>

Effects of valsartan and U0126 on atrial fibrosis and connexin40 remodeling in rats / 中华心血管病杂志

<p><b>OBJECTIVE</b>To explore the effects of valsartan and MEK1/2 inhibitor U0126 on atrial fibrosis and connexin40 (Cx40) remodeling in rats treated with isoproterenol (ISO).</p><p><b>METHODS</b>32 male SD rats were randomly divided into control group (A), ISO (5 mg · kg(-1) · d(-1) for 7 days) + DMSO group (B), ISO + U0126 (0.5 mg · kg(-1) · d(-1) for 28 days) group (C, U0126 was dissolved in DMSO), ISO + valsartan (30 mg · kg(-1) · d(-1) for 28 days) + DMSO group (D). Rats were sacrificed after 28 days. The AngIIcontent in myocardial tissue was measured by radioimmunoassay, P-MEK1/2, P-ERK1/2 and Cx40 was detected by immunohistochemistry, atrial fibrosis was determined on HE and Masson stained heart sections.</p><p><b>RESULTS</b>The content of AngII was significantly higher in group B, C and D compared with group A [(368.243 ± 6.283) ng/L, (357.175 ± 5.944) ng/L, (359.908 ± 2.496) ng/L vs (250.380 ± 4.261) ng/L, P < 0.01]; the degree of atrial fibrosis was significantly lower in group C and D compared with group B [CVF(10.260 ± 0.525)%, (10.238 ± 0.524)% vs (78.710 ± 1.587)%, P < 0.01] while there was no atrial fibrosis in group A [CVF(9.025 ± 0.456)%]; the expression of P-MEK1/2 and P-ERK1/2 was significantly upregulated in group B compared with group A (P-MEK1/2: 0.311 ± 0.007 vs 0.203 ± 0.009, P < 0.01; P-ERK1/2: 0.259 ± 0.003 vs 0.173 ± 0.006, P < 0.01) and significantly lower in group C and D compared with group B (P-MEK1/2: 0.212 ± 0.004, 0.213 ± 0.005 vs 0.311 ± 0.007, P < 0.01, P-ERK1/2: 0.178 ± 0.004, 0.175 ± 0.007 vs 0.259 ± 0.003, P < 0.01). The content of Cx40 was obviously reduced and the distribution of Cx40 was disordered in group B compared with A (0.199 ± 0.007 vs 0.241 ± 0.004, P < 0.01) which could be partly reversed in group C and D (0.239 ± 0.037, 0.235 ± 0.006 vs 0.199 ± 0.007, P < 0.01). All parameters in group C and D were similar (P > 0.05).</p><p><b>CONCLUSION</b>The chronically elevated AngII content in myocardium may be related to atrial fibrosis and Cx40 remodeling in this model, valsartan and U0126 were equivalent on attenuating atrial fibrosis and Cx40 remodeling by inhibiting ERK pathways at different levels.</p>