Activation of calcium-sensing receptors is associated with apoptosis in a model of simulated cardiomyocytes ischemia/reperfusion

Objective： Calcium-sensing receptors （CaSRs） are G-protein coupled receptors which maintain systemic calcium homeostasis and participate in hormone secretion, activation of ion channels, cell apoptosis, proliferation, and differentiation. Previous studies have shown that CaSRs induce apoptosis in isolated adult rat heart and in normal neonatal rat cardiomyocytes by G-protein-PLC-IP3 signaling transduction. However, little knowledge is presently available concerning the role of CaSRs in the apoptosis induced by ischemia and reperfusion in neonatal cardiomyocytes. Methods： Primary neonatal rat ventricular cardiomyocytes were incubated in ischemiamimetic solution for 2 h, and then re-incubated in normal culture medium for 24 h to establish a model of simu- lated ischemia/reperfusion （I/R）. Cardiomyocyte apoptosis was detected by terminal deoxynucleotidyl transferase- mediated dUTP nick end labeling （TUNEL）. The expression of CaSRs mRNA was detected by real-time reverse transcription polymerase chain reaction （RT-PCR）. In addition, the expressions of caspase-3 and Bcl-2 were analyzed by western blot. Results： The simulated I/R enhanced the expression of CaSRs and cardiomyocyte apoptosis. GdCl3, a specific activator of CaSRs, further increased the expression of CaSRs and cardiomyocyte apoptosis, along with up-regulation of caspase-3 and down-regulation of Bcl-2. Conclusion： CaSRs are associated with UR injury and apoptosis in neonatal rat ventricular cardiomyocytes via suppressing Bcl-2 and promoting caspase-3 expression.

The genetic framework for development of nephrolithiasis

Over 1%-15% of the population worldwide is affected by nephrolithiasis,which remains the most common and costly disease that urologists manage today.Identification of atrisk individuals remains a theoretical and technological challenge.The search for monogenic causes of stone disease has been largely unfruitful and a technological challenge;however,several candidate genes have been implicated in the development of nephrolithiasis.In this review,we will review current data on the genetic inheritance of stone disease,as well as investigate the evolving role of genetic analysis and counseling in the management of nephrolithiasis.

Involvement of CaSR in Hyperglycemia-induced Macroangiopathy and Related Mechanism

In order to clarify the potential role of calcium sensing receptor（Ca SR）, a typical G protein coupled receptor（GPCR）, in hyperglacemia-induced macroangiopathy, experimental hyperglycemia models in vivo and in vitro were prepared. Firstly, SD rats were divided into control group（n=10） and diabetes group（n=10）, and diabetic model was induced via high-fat diet feeding and streptozotocin（STZ, 30 mg/kg） injection. Hydroxyproline level, determined via Choramnie T oxidation method, in vessel wall in diabetic rats was 30% more than that in control group. The gene transcription and expression levels were detected by real-time PCR and Western blotting, respectively. Both of collagen Ⅰ and Ⅲ mR NA levels in diabetic aorta were nearly twice those in normal aorta. The cleaved caspase-3 and-9 were elevated 1.5 and 2.5 times respectively in diabetic vascular cells. As compared with controls, m RNA and protein levels of CaS R in aorta were increased by 3 and 1.5 times in diabetes group. The expression levels of Bax as well as pro-apoptotic kinases（phospho-p38 and phosphor-JNK） were also increased 2, 0.5 and 0.5 times respectively in diabetic rats. To further validate the involvement of Ca SR in cell apoptosis and explore the potential mechanism, the endothelial cell line（human umbilical vascular endothelial cells, HUVECs） was stimulated with high concentration of glucose（33 mmol/L） to mimic hyperglycemia in vitro. Cell-based assays also showed that the Ca SR level and key apoptotic proteins（cleaved caspase-3 and-9, Bax, phospho-p38 and phosphor-JNK） were elevated in response to stimulation, and inhibition of Ca SR by using specific inhibitor（NPS-2143, 10 μmol/L） could protect cells against apoptosis. Our results demonstrated that Ca SR might take important part in the development of diabetic macroangiopathy through promoting cell apoptosis induced by hyperglycemia.

Progress in the Clinical Application of Cinacalcet in the Treatment of Secondary Hyperthyroidism

Secondary hyperthyroidism(SHPT)is a common complication of maintenance hemodialysis(MHD).In China the prevalence of chronic kidney disease(CKD)is 10.8%and there are about 0.2 million patients treated with maintenance hemodialysis.These number are still increasing.Cinacalcet is a new calcium sensing receptor agonist to treat SHPT and the first calcimimetics be approved by Food and Drug Administration(FDA)to treat human.It can activate the calcium sensing receptor in parathyroid to improving control of parathyroid hormone(PTH),serum calcium,phosphorus,and calcium phosphorus product.Then decrease vascular calcification and parathyroid gland volume and reduce the occurrence of fracture and calcific uremic arteriolopathy(CUA).A better understanding of the clinical evaluation for Cinacalcet will hopefully help us to reduce the incidence of SHPT.

Amino acid sensing in the gut and its mediation in gut-brain signal transduction

Animal gastrointestinal tract is not only a digestive organ, but also a nutrient sensing organ which detects luminal nutrient and thus can regulate food intake. There are many amino acid sensing receptors and transporters in the gut. Amino acids sensing by these receptors and transporters can stimulate the intestinal endocrine cells to release a variety of gut hormones. These hormones trigger a series of physiological effects via the nerve system. This review summarized the recent advance on the amino acid sensing receptors and transporters in the gastrointestinal tract, the gut hormones released from the intestinal endocrine cells and the hormones-induced signal transduction between the gut and brain. A better understanding of these processes may help to gain further insight into the specific role of amino acids in digestion and provide guidelines in developing strategy for the better use of amino acids in the diet.