Presence of autoantibodies against β1-adrenoceptor aggravates the kidney injury in rats / 生理学报

Since the autoantibodies against the second extracellular loop of β(1)-adrenoceptor (β(1)-AABs) have been found in the sera of patients with idiopathic dilated cardiomyopathy (IDCM), the involvement of autoimmune mechanisms in the pathogenesis of many cardiovascular diseases has extensively been investigated. Our previous study found that urinary occult blood and protein excretion were frequently found in the rats with positive β(1)-AABs, but the mechanisms are unclear. Therefore, we infused the β(1)-AABs into the vein periodically in an attempt to investigate whether β(1)-AABs could induce morphological and functional changes in the kidneys of adult and aged rats and explore the possible mechanisms. The synthetic peptide according to the sequences of the second extracellular loop of β(1)-adrenoceptor (β(1)-AR-ECII) was used to immunize the adult rats to acquire enough β(1)-AABs for use. Neonatal rat ventricular myocytes (NRVMs) culture was used to observe the biological effects of β(1)-AABs on the beating rate. The purified β(1)-AABs were transfused into the vein of rats. The sera level of blood urea nitrogen (BUN), creatinine (CR), uric acid (UA), urinary specific gravity, protein excretion, occult blood and urinary glucose were detected at the different time points by biochemistry and urine analyzers. HE and Masson's trichrome staining were used to detect the changes in kidney structure of passively immunized rats. Enhanced green fluorescent protein (EGFP) and β(1)-AR-EGFP plasmids were transfected into the human embryonic kidney 293 (HEK293) cells in order to observe the changes in cell injury with the treatment of β(1)-AABs. It was found that the sera level of BUN, CR and UA increased gradually and the ratio of BUN to CR decreased progressively with the administration of β(1)-AABs. The increasing of proteinuria, urinary occult blood and urinary glucose was detected by urine analyzer in β(1)-AABs group. By HE and Masson's coloration, lots of mononuclear cell infiltration and collagen fibers deposition could be observed at the 24th week of immunization. After the treatment of β(1)-AABs, the caspase-3 activity increased significantly in the HEK293 cells transfected with β(1)-AR-EGFP plasmids, while no significant changes were observed for lactate dehydrogenase (LDH) activity. The results indicate that long-term presence of β(1)-AABs can induce the morphological and functional damage of the kidneys in adult and aged rats.

The up-regulation of hypoxia inducible factor-1α by hypoxic postconditioning reduces hypoxia/reoxygenation-induced injury in heart-derived H9c2 cells / 生理学报

The aim of the present study was to explore the effects of hypoxic postconditioning (PostC) on heart-derived H9c2 cells injury induced by hypoxia/reoxygenation (H/R) and the expression of hypoxia inducible factor-1α (HIF-1α), and to analyze the relationship between them. Cultured H9c2 cardiac muscle cells were subjected to 3-hour hypoxia and 2-hour reoxygenation to simulate ischemia and reperfusion, or underwent 3 cycles of 5-min reoxygenation and 5-min hypoxia preceding the long reoxygenation to simulate ischemic postconditioning. Cell viability, lactate dehydrogenase (LDH) activity, and caspase-3 activity were detected respectively to investigate the cell injury induced by H/R. The level of HIF-1α mRNA was measured by real-time PCR. Western blot was used to determine HIF-1α protein level. The results showed that postconditioning significantly increased H9c2 cell viability, reduced the activity of LDH and caspase-3. Simultaneously, postconditioning up-regulated the HIF-1α protein level. Moreover, after DMOG, an inhibitor of proline hydroxylase (PHD) which targeted to HIF-1α degradation, was used to stabilize HIF-1α protein level, the reduction of H9c2 cells injury was comparable to that by postconditioning. There was a significant linear positive relationship between HIF-1α protein level and cell viability (r = 0.743, P < 0.01). After HIF-1α gene was silenced by siRNA, the cardio-protective effects of postconditioning was significantly weakened. These data suggest that up-regulation of HIF-1α plays an important role in the cardio-protection of postconditioning.

The attenuation of myocardial susceptibility to ischemia/reperfusion injury by ischemic postconditioning in hypercholesteremia rats and the role of hypoxia inducible factor-1alpha / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To explore whether ischemic postconditioning can attenuate the myocardial injury induced by ischemia/reperfusion (I/R) in hypercholesteremic rats and whether hypoxia inducible factor-1alpha (HIF-1alpha) play a role in the protection.</p><p><b>METHODS</b>Adult male Wistar rats received a high fat diet for 8 weeks to prepare the hypercholesteremic models. Myocardial damage induced by ischemia/reperfusion was evaluated by infarct size, creatine kinase (CK) activity and myocardial apoptosis. HIF-1alpha mRNA level was detected by real time-RT-PCR and the protein level was detected by Western blot.</p><p><b>RESULTS</b>Myocardial infarct size, CK activity, and caspase-3 activity induced by I/R were markedly increased in hypercholesteremic rats compared with those in normal rats. Ischemic postconditioning attenuated the myocardial injury in both normal rats and hypercholesteremic rats, and increased HIF-1alpha protein level. There was a significant linear inverse relationship between HIF-1alpha protein level and infarct size (r = -0.802, P <0.01).</p><p><b>CONCLUSION</b>Hypercholesteremia enhanced the susceptibility of myocardia to ischemia/reperfusion injury. While ischemic postconditioning markedly attenuated the increase of myocardial susceptibility to I/R induced by hypercholesteremia. HIF-1alpha might be one of the mechanisms of protection by ischemic postconditioning.</p>

Detection of serum autoantibodies against AT₁A-receptor during the development of the four types of hypertensive rat models / 生理学报

Using two-kidney one-clip renal hypertensive (2K1C group), stress-induced hypertensive (neural group), DOCA-salt treated hypertensive (DOCA group) and spontaneously hypertensive rats (SHR group), to investigate the change in AT(1A)-receptor autoantibodies (AT(1A)-AAs) during the development of the four types of hypertension. The biological activities of AT(1A)-AAs were examined. It was shown that the frequency of occurrence and titres of AT(1A)-AAs increased significantly during the development of hypertension. In the four hypertensive groups studied, the occurrence of AT(1A)-AAs was most prominent in SHR, 2K1C and neural groups. The biological effects of AT(1A)-AAs were shown to increase the beating frequency of cultured neonatal myocardial and vascular contractile tension. It is suggested that autoimmune mechanisms are involved the pathogenesis of different types of hypertension and the AT(1A)-AAs may be one of the mechanisms leading to cardiac hypertrophy.

Comparative studies of vasodilating effects of angiotensin-(1-7) on the different vessels / 生理学报

The purpose of this study was to compare the vasodilating effects of angiotensin-(1-7) [Ang-(1-7)] on the different vessels and to clarify its mechanisms by using relaxing responses of preconstricted vascular rings. The results showed: (1) Ang-(1-7) dose-dependently induced vasorelaxation in all the vessels studied. However, there is apparent heterogeneity in the responsiveness of vessels from different origin. (2) The Ang-(1-7)-induced vasorelaxation was endothelium dependent and largely mediated by NO system. (3) The vasodilator action of Ang-(1-7) was not mediated by AT1 or AT2 receptor subtypes. It is suggested that the Ang-(1-7)-induced vasorelaxation is endothelium dependent by some other unclarified angiotensin receptor subtypes and is largely mediated by NO system.

The study of susceptibility to ischemia-reperfusion injury in heart of aged rat / 中华老年医学杂志

Objective To determine whether the susceptibility to ischemia-reperfusion injury in aged heart is higher than that in adult heart and,if so,to clarify the mechanisms underlying this change.Methods Wister rats(5-or 20-month-old)were randomly divided into 4 groups(6 animals in each group).The rats were subjected to 30 minutes of myocardial ischemia via ligating the left anterior descending coronary artery,followed by 3 hours of reperfusion(Young-MI/R group and Old-MI/R group);A silk suture around the left anterior descending coronary artery was not ligated in young and old rats(Young-sham group and Old-sham group).Myocardial apoptosis was detected by terminal deoxynueleotidyl transferase biotin-d UTP nick end labeling(TUNEL)staining and caspase-3 activity was detected by using a caspase-3 colorimetrie assay.Nitrotyrosine content,a footprint of in vivo ONOO~-formation,and total NO content were determined by ELISA and chemiluminescence method respectively.Results A significantly exacerbated cardiac reperfusion injury was found in Old-MI/R group as evidenced by increased TUNEL positive myocytes[(19.0?2.1)% vs.(14.6?1.7)%],and increased myocardial caspase-3 activity[(436?35)?mool/mg vs.(340?32)?mol/mg] compared with Young-MI/R group(P＜0.05).Aged hearts had a markedly increased basal NOx level compared with young adult hearts.Marked higher myocardial nitrotyrosine content was found in OId-MI/R group[(7.25?0.18)nmol/g]than that in Young-MI/R group[(4.68?0.15)nmol/g] (P＜0.05).Conclusions In aged hearts,high levels of NO might form highly toxie derivant, ONOO~-,and its subsequent nitrified protein.This may attribute to the increased susceptibility of the aged heart to isehemic-reperfusion injury.

Effect of losartan on produce of sera autoantibodies to angiotensin II-1 receptor in renovascular hypertension rats / 中国应用生理学杂志

<p><b>AIM AND METHODS</b>The effects of losartan (after operation 2 week to 10 week, 5 mg/kg d ig) on generation of AT1R-AA in sera were observed during development of hypertension in rats. The renovascular hypertension (RVH) model was established by two-kidney one-clip method, a synthetic peptide corresponding to amino acid sequence 165-191 of the second extracellular loop of the angiotensin II-1 receptor (AT1R) was used as antigen, SA-ELISA were used to examine sera AT1R autoantibody (AT1R-AA).</p><p><b>RESULTS</b>The frequencies and titres of AT1R-AA after operation one week rats were significantly increased (P < 0.05). The treatment with losartan not only inhibited structural and functional changes, but also the frequencies and titres of AT1R-AA was significantly lower (P < 0.05) than RVH group.</p><p><b>CONCLUSION</b>It is suggested that the losartan significantly inhibits generation of the AT1R-AA.</p>

Changes in autoantibody against cardiovascular AT1-receptor during development of renovascular hypertension in rats / 生理学报

The aim of this study was to observe the change in angiotensin II receptor subtype 1 (AT(1)) autoantibody during the development of renovascular hypertension (RVH). The Goldblatt renovascular hypertension model was established by the two-kidney one-clip method, and a synthetic peptide corresponding to amino acid sequence 165-191 of the second extracellular loop of the AT(1)-receptor was used as the antigen. Sera AT(1)-receptor autoantibody was detected by SA-ELISA. It was shown that two weeks after operation both the frequency of occurrence and the titre of autoantibodies to AT(1)-receptor were significantly increased as compared with the pre-treatment control. The increase in autoantibodies lasted several weeks and then decreased gradually to the pre-clipping level at 12 weeks. It is suggested that autoimmune mechanisms are involved in the pathogenesis of renovascular hypertension and the AT(1) autoantibodies may be one of the mechanisms leading to cardiac hypertrophy.