ABSTRACT
In order to clarify the potential role of calcium sensing receptor (CaSR), 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 mRNA 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, mRNA and protein levels of CaSR 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 CaSR 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 CaSR 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 CaSR by using specific inhibitor (NPS-2143, 10 μmol/L) could protect cells against apoptosis. Our results demonstrated that CaSR might take important part in the development of diabetic macroangiopathy through promoting cell apoptosis induced by hyperglycemia.
Subject(s)
Animals , Humans , Rats , Diabetic Angiopathies , Human Umbilical Vein Endothelial Cells , Hyperglycemia , Receptors, Calcium-Sensing , PhysiologyABSTRACT
In order to clarify the potential role of calcium sensing receptor (CaSR), 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 mRNA 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, mRNA and protein levels of CaSR 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 CaSR 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 CaSR 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 CaSR by using specific inhibitor (NPS-2143, 10 μmol/L) could protect cells against apoptosis. Our results demonstrated that CaSR might take important part in the development of diabetic macroangiopathy through promoting cell apoptosis induced by hyperglycemia.
ABSTRACT
The goal of this study was to determine the effects of the L-type calcium channel blockers verapamil and diltiazem on the currents of voltage-gated potassium channel [fKvl.4deltaN], an N-terminal-deleted mutant of the ferret Kvl.4 potassium channel. Measurements were made using a two electrode voltage clamp technique with channels expressed stably in Xenopus oocytes. The fKvl.4deltaN currents displayed slow inactivation, with a half-inactivation potential of-38.38 mV and slow recovery from inactivation [T = 1.90 seconds at -90 mV]. The fKv 1.4deltaN currents exhibited state-dependent blockade by both drugs, and the inhibition was frequency-, voltage-, and concentration-dependent, consistent with open channel block. Verapamil and diltiazem blocked fKvl.4deltaN currents with 50% inhibitory concentration [IC[50] values of 260.71 +/- 18.50 micromol/L and 241.04 +/- 23.06 micromol/L, respectively. Verapamil accelerated the C-type inactivation rate and slowed recovery of the fKv 1.4delta N channel, while shifting the steady activation curve to the right. Blockade of fKvl.4deltaN currents by diltiazem was similar to that of verapamil, but diltiazem accelerated the decay rate of inactivation of fKv 1.4 deltaN currents without modifying the kinetics of current activation. The present results suggest that verapamil and diltiazem accelerate the C-type inactivation and slow the recovery of the fKv 1.4 deltaN channel in the open state
ABSTRACT
<p><b>BACKGROUND</b>Bradykinin (BK) acts mainly on two receptor subtypes: B(1) and B(2), and activation of B(2) receptor mediates the most well-known cardioprotective effects of angiotensin converting enzyme inhibitors (ACEi), however, the role that B(1) receptor plays in ACEi has not been fully defined. We examined the role of B(1) receptor in the inhibitory effect of ACE inhibitor captopril on rat cardiomyocyte hypertrophy and cardiac fibroblast proliferation induced by angiotensin II (Ang II) and explored its possible mechanism.</p><p><b>METHODS</b>Neonatal cardiomyocytes and cardiac fibroblasts (CFs) were randomly treated with Ang II, captopril, B(2) receptor antagonist (HOE-140) and B(1) receptor antagonist (des-Arg(10), Leu(9)-kallidin) alone or in combination. Flow cytometry was used to evaluate cell cycle, size and protein content. Nitric oxide (NO) and intracellular cyclic guanosine monophosphate (cGMP) level were measured by colorimetry and radioimmunoassay.</p><p><b>RESULTS</b>After the CFs and cardiomyocytes were incubated with 0.1 micromol/L Ang II for 48 hours, the percentage of CFs in the S stage, cardiomyocytes size and protein content significantly increased (both P < 0.01 vs control), and these increases were inhibited by 10 micromol/L captopril. However, NO and cGMP levels were significantly higher than that with Ang II alone (both P < 0.01). 1 micromol/L HOE-140 or 0.1 micromol/L des-Arg(10), Leu(9)-kallidin attenuated the effects of captopril, which was blunted further by blockade of both B(1) and B(2) receptors.</p><p><b>CONCLUSIONS</b>Acting via B(2) receptor, BK contributes to the antihypertrophic and antiproliferative effects of captopril on cardiomyocytes and CFs. In the absence of B(2) receptor, B(1) receptor may act a compensatory mechanism for the B(2) receptor and contribute to the inhibition of cardiomyocyte hypertrophy and CFs proliferation by captopril. NO and cGMP play an important role in the effect of B(1) receptor.</p>