ABSTRACT
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.