Resistin-like molecule alpha enhances the proliferation and migration of aortic vascular smooth muscle cells.

OBJECTIVE: The mitogenic and chemotactic effects of resistin-like molecule alpha (RELMα) are thought to contribute to vascular remodeling in pulmonary arterial hypertension. Here we evaluate the expression of RELMα in atherosclerotic plaque and investigate its effects on the proliferation and migration of vascular smooth muscle cells (VSMCs). METHODS: An atherosclerotic model was established by feeding 4-week-old C57BL/6J ApoE-/- mice (n = 9) with a high-fat diet. Wild-type 4-week-old C57BL/6J (n = 9) were fed the same diet and were used as controls. RELMα expression was evaluated by immunohistochemistry and quantified using real-time PCR (RT-PCR). A (3)H-thymidine incorporation assay and the Boyden chamber assay, respectively, were used to explore the effects of different concentrations of RELMα on the proliferation and migration of VSMCs. RESULTS: Immunohistochemistry identified positively stained granules in atherosclerotic plaques. These results were confirmed by detection of RELMα mRNA using RT-PCR. We also demonstrated that in vitro exposure to RELMα significantly promoted the proliferation and migration of VSMCs in a dose-related manner (p < 0.01). CONCLUSIONS: RELMα expressed in atherosclerotic plaque of ApoE-/- mice appears to enhance the proliferation and migration of aortic VSMCs in a dose-related manner.

[Prevention of atherosclerotic plaque development by modulating heme oxygenase-1-endogenous carbon monoxide system in rabbit model].

OBJECTIVE: To investigate the effect of heme oxygenase/carbon monoxide (HO-1/CO) system on lipid deposition at aortic intima and the mechanism involved in hyperlipidemic rabbits. METHODS: Totally 32 rabbits, were divided into four groups. One group as control. Three groups for the following treatments: 1.5% cholesterol ration (Ch group, n = 8); 1.5% cholesterol ration plus HO-1 inducer hemin (Hm group, n = 8); and instead of hemin, the HO-1 inhibitor, zinc protoporphyrin IX (Zn group, n = 8) was given by injection into the abdominal cavity. Experiments were lasted for 12 weeks. Rabbit aortas were then isolated as the samples for histopathologic and ultrastructural examination. The protein expressions of HO-1 and endothelin-1 (ET-1) were investigated by immunohistochemical staining and Western blot analysis. RESULTS: Comparing with the Ch group, rabbits of the Hm group showed a remarkably less extent of lipid deposition at the aortic intima [(17.9 ± 3.0)% vs (54.0 ± 4.2)%], and rabbits of the Zn group had a marked extent of lesion development [(61.1 ± 3.5)%]. Lipid deposition, endothelial damage and neo-intimal formation were less severe in rabbits of the Hm group than those in the Zn or Ch group, respectively. Comparing with the control group, rabbits of the Ch group showed a significant decrease of aortic NO production and cNOS activity. However, there were an enhancement of CO production and HO-1 activity (P < 0.01). Compared with Ch group, rabbits of the Hm group showed a remarkable elevation of aortic HO activity and CO production, whereas rabbits of the Zn group showed a marked decrease of both parameters. Compared with the Ch group, rabbits of the Hm group demonstrated a marked reduction of aorta ET-1 expression, whereas Zn group had a significantly higher ET-1 expression. CONCLUSIONS: Modulation of HO-1/CO system may improve vascular endothelial function and inhibit smooth muscle cell proliferation in hypercholesterolemic rabbits, likely through a compensatory mechanism and a reduction of ET-1 expression, eventually leading to an inhibition of atherosclerotic plaque development.

Effect of the haeme oxygenase-1/endogenous carbon monoxide system on atherosclerotic plaque formation in rabbits.

BACKGROUND: To investigate the effect of the haeme oxygenase-1/carbon monoxide (HO-1/CO) system on atherosclerotic plaque formation and its possible mechanism. METHODS: For 12 weeks, rabbits were given a 1.5% cholesterol diet (Ch group, n = 8) or a 1.5% cholesterol diet plus an HO-1 inducer, haemin (Hm group, n = 8), or an HO-1 inhibitor, zinc protoporphyrin IX (Znpp-IX, Zn group, n = 8) by intraperitoneal injection. RESULTS: Compared with the normal control group (C group, n = 8), serum levels of lipids and oxidised low-density lipoproteins (ox-LDL) increased significantly in all experimental groups (p < 0.01). However, no significant differences were observed among the three experimental groups (p > 0.01). Compared with the control group, aortic nitric oxide (NO) production and nitric oxide synthase (cNOS) activity decreased markedly, whereas carbon monoxide (CO) production and HO-1 activity increased markedly in the Ch group (p < 0.01). This was associated with an increase in the area of aortic plaque of 54.00 ± 4.16%. Compared with the Ch group, CO production and HO-1 activity increased markedly, while aortic HO activity and CO production decreased significantly in the Hm group. The area of aortic plaque was significantly reduced in the Hm group (17.88 ± 3.01%), whereas the area of aortic plaque was significantly increased in the Zn group (61.13 ± 3.50%). Compared with the Ch group, aortic endothlin-1 expression in the Hm group reduced significantly, while in the Zn group it was significantly higher than in the Ch group (p < 0.01). CONCLUSION: The HO-1/CO system plays an inhibitory role in atherosclerotic plaque formation. This role was not mediated by regulating serum lipids and ox-LDL, but was related to the reciprocal relationship between the HO-1/CO and NOS/NO systems in atherosclerosis and the down-regulated expression of endothlin-1 (ET-1), which inhibits the proliferation of vascular smooth muscle cells.

High serum resistin level may be an indicator of the severity of coronary disease in acute coronary syndrome.

OBJECTIVE: To investigate the correlation between serum resistin level, cardiovascular risk factors and severity of coronary disease in acute coronary syndrome (ACS). METHODS: After evaluated by clinical history, electrocardiography, exercise tolerance tests, laboratory tests, and coronary angiography, 220 consecutive patients with suspected chest pain were divided into normal control group, stable angina pectoris (SAP) group, and ACS group, respectively. Baseline clinical characteristics, including height, weight, waist circumference, hip circumference, white blood cell count, high-sensitive C-reactive protein (hsCRP), total cholesterol, triglyceride, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol, were compared among three groups. ELISA was used to detect serum resistin levels. Pearson's correlation coefficient analysis was used to assess association between resistin and other traditional cardiovascular risk factors. Multinomial logistic regression analyses were used to define the relationship between serum resistin level and SAP or ACS. RESULTS: Serum resistin level in ACS group (1.18+/-0.48 microg/L) was significantly higher than that in normal control and SAP groups (0.49+/-0.40 and 0.66+/-0.40 microg/L; P<0.01). Only in ACS group, increased serum resistin level was significantly correlated with hsCRP (r=0.262, P=0.004) and white blood cell count (r=0.347, P=0.001). Furthermore, serum resistin levels showed a stepwise increase with the number increase of > 50% stenosed coronary vessels. Multinomial logistic regression test demonstrated that serum resistin was a strong risk factor for ACS (OR=29.132, 95 % CI: 10.939-77.581, P<0.001). CONCLUSION: These findings suggested the potential role of resistin in atherosclerosis and especially its involvement in ACS.

[Apoptosis of hypertrophic cardiomyocytes stimulated by hypoxia-reoxygenation is partially mediated by apoptosis-inducing factor].

Cardiomyocyte apoptosis leads to the functional incapacitation of myocardial plasmodium and plays an important role in the pathogenesis of heart failure transformed from compensable cardiac hypertrophy. Mitochondria are the main source of apoptosis-inducing molecule of various cells, and the role of caspartate-specific cysteinyl proteinase (caspase)-dependent mechanism has generally been accepted in the cardiomyocyte apoptosis. However, the significance of caspase-independent apoptosis-inducing factor (AIF) mechanism is not yet understood. The purpose of this study was to evaluate hypoxia-reperfusion-induced alterations of AIF mRNA and protein expressions in hypertrophic cardiomyocytes. Cardiomyocyte hypertrophy was produced by angiotensin II (0.1 mumol/L). The cells were cultured under the condition of hypoxia (95% N2 and 5% CO2; the O2 partial pressure was lower than 5 mmHg) for 8 h or 12 h (named as H8h and H12h groups, respectively), and then exposed to normal culture environment (named as H8h/R and H12h/R groups, respectively). Apoptosis was detected with Hoechst 33258 staining. The AIF mRNA and protein expressions were detected by RT-PCR and Western blot and quantified by gel scanning. The results were as follows: (1) The level of AIF mRNA expression was 0.29+/-0.08 (optical density, relative value) in the control group (hypertrophic cardiomyocytes cultured in normal environment). Compared with that in the control group, the levels of AIF mRNA expression were significantly higher in the groups of H8h and H12h (0.52+/-0.04 and 0.85+/-0.10), indicating that this effect was time-dependent. A further increase of AIF mRNA expression was observed in the groups of H8h/R (1.09+/-0.12) and H12h/R (1.41+/-0.23). (2) The level of AIF protein expression was 0.29+/-0.04 in the control group. Compared with that in the control group, the levels of AIF protein expression were significantly higher in the groups of H8h and H12h (2.07+/-0.15 and 3.12+/-0.19). The AIF protein expression was increased further in the groups of H8h/R (4.57+/-0.25) and H12h/R (5.71+/-0.27). The nuclear translocation of AIF protein was obvious only in the groups of H8h/R and H12h/R. (3) The expressions of AIF mRNA and protein were almost completely inhibited by AIF siRNA transfection. The siRNA transfection also reduced the apoptosis of hypertrophic cardiomyocytes in the groups of H8h/R and H12h/R but not in the groups of H8h and H12h. The apoptosis rate was significantly reduced by both AIF siRNA transfection and Ac-DEVD-cmk, an inhibitor of caspase-3. This reduction induced by two factors was more evident than that by one factor. (4) AIF nuclear translocation induced by hypoxia-reperfusion was not affected by inhibition of the activity of caspase-3. These data suggest that AIF plays a pivotal role in the apoptosis of hypertrophic cardiomyocytes induced by hypoxia-reperfusion.

[Heme oxygenase-1 and carbon monoxide are key mediators for vascular smooth muscle cells proliferation induced by insulin-like growth factor-I].

OBJECTIVE: To determine the role and related mechanisms of heme oxygenase-1/carbon monoxide (HO-1/CO) on VSMCs proliferation induced by insulin-like growth factor-I (IGF-I). METHODS: VSMCs isolated from rabbit aorta were cultured in vitro and proliferation was induced by IGF-I. Hemin (a substrate and inducer of HO-1) or zinc protoporphyrin-IX (Znpp-IX, an inhibitor of HO-1) was added to stimulate or inhibit the expression of HO-1. The mRNA and protein expressions of HO-1 were detected by RT-PCR and Western blot analysis. CO released into the culture media was quantitated by measuring carbon monoxide hemoglobin (COHb), VSMCs proliferation and cell cycle were determined by (3)H-TdR incorporation assay and flow cytometry, respectively. RESULTS: The HO-1 mRNA and protein expressions in VSMCs and the amount of COHb in the culture media were significantly increased and the IGF-I-induced (3)H-TdR incorporations of VSMCs significantly reduced by hemin in a dose-dependent manner (P < 0.01). Furthermore, VSMCs in the G(0)/G(1) phase were increased and in the S and G(2)/M phase decreased by hemin (P < 0.01). Opposite results were observed in VSMCs treated with Znpp-IX. CONCLUSIONS: Endogenous HO-1 and CO are important mediators for inhibiting IGF-I induced VSMCs proliferation by reducing VSMCs DNA synthesis and decelerating cell cycle progression.

[Relationship between apoptosis and alteration of the energetic metabolism pathways of hypertrophic cardiomyocytes induced by hypoxia-reoxygenation].

The apoptosis of cardiomyocytes plays a pivotal role in the pathogenesis of cardiac failure transformed from cardiac hypertrophy, so that suppression of cardiomyocytes apoptosis is an effective pharmacotherapeutic target to prevent cardiac failure. This study focused on the relationship between apoptosis and alteration of the energetic metabolism pathways of hypertrophic cardiomyocytes induced by hypoxia-reoxygenation. Cardiomyocyte hypertrophy was induced by angiotensin II (0.1 mumol/L ) and norepinephrine (1 mumol/L), and the cells were cultured under the condition of hypoxia ( 95% N2 and 5% CO2, the O2 partial pressure was regulated at least lower than 5 mmHg ) for 8 h, then were recovered to normal culture environment. Apoptosis was detected with TUNEL. The activity of pyruvate dehydrogenase (PDH) and carnitine palmitoyltransferase 1 (CPT-1), the rate of glycose oxidation and glycolysis, and fatty acid metabolism were detected by liquid scintillation counting. The results are as follows: (1) The activity of active PDH (PDHa) was slightly higher in hypertrophic cardiomyocytes than that in normal cardiomyocytes, but the activity of CPT-1 was significantly lower in hypertrophic cardiomyoctes than that in normal cardiomyocytes.Compared with the hypertrophic cardiomyocytes cultured with normal oxygen concentration, the activities of PDHa and CPT-1 were decreased significantly after hypoxia for 8 h, and the activity of PDHa were decreased further after reoxygenation for 4 h, but the activity of CPT-1 recovered quickly after reoxygenation. (2) The rate of glucose oxidation in hypertrophic cardiomyocytes increased slightly when cultured under normal O2 partial pressure than that in normal cardiac cells. The rate of glucose oxidation reduced (16 +/- 0.9)% and (48 +/- 1.1)% in normal and hypertrophic cardiomyocytes, respectively, after hypoxia. It reduced further in hypertrophic cardiac cells at 4 h of reoxygenation, then recovered gradually. In normal cardiocytes, it recovered quickly after reoxygenation. (3) The rate of glycolysis of hypertrophic cardiocytes increased slightly than that of the normal cardiocytes when cultured in the general O(2) environment. Compared with the normal cardiomyocytes, the rate of glycolysis of hypertrophic cardiac cells was the same during hypoxia-reoxygenation culture, i.e., the rate of glycolysis decreased slightly after hypoxia for 8 h, but increased rapidly and significantly after reoxygenation. (4) The rate of fatty acid oxidation was slightly lower in hypertrophic cardiocytes than that in normal cardiomyocytes. After hypoxia for 8 h, the rate of fatty acid oxidation decreased significantly in normal and hypertrophic cardiomyocytes, there was no difference between normal and hypertrophic cardiomyocytes. But the alterations of fatty acid oxidation after reoxygenation were different between normal and hypertrophic cardiac cells, namely, the fatty acid oxidation of normal cardiomyocytes were activated slowly and slightly, while the rate of fatty acid oxidation of hypertrophic cardiomyocytes increased markedly at the early stage of reoxygenation, and increased further at 8 h of reoxygenation. (5) The rate of apoptosis in hypertrophic cardiocytes increased obviously after hypoxia for 8 h, and increased further and markedly at the early stage of reoxygenation, then gradually decreased to normal level. (6) Dicholoroacetate could inhibit apoptosis of hypertrophic cardiocytes through increasing glucose oxidation and inhibiting the activation of glycolysis and fatty acid oxidation of hypertrophic cardiomyocytes induced by hypoxia-reoxygenation. These data demonstrate that apoptosis in hypertrophic cardiomyocytes after hypoxia-reoxygenation is mainly due to the inhibition of glucose oxidation and the activation of glucolysis and fatty acid oxidation. Furthermore, increasing glucose oxidation may be a new pharmacotherapeutic target to inhibit apoptosis of hypertrophic cardiac cells.

[Change and correlation of heme oxygenase/carbon monoxide and nitric oxide synthase/nitrogen monoxide system in atherosclerotic progress of rabbits].

OBJECTIVE: To investigate the change and correlation of carbon monoxide/heme oxygenase and nitrogen monoxide/nitric oxide synthase system in atherosclerosis and the influence of the two systems on atherosclerotic progress. METHODS: The rabbits received 1% cholesterol diet (chol group, n = 8), or 1% cholesterol diet plus L-arginine (L-arg group, n = 8) or L-NAME (L-NAME group, n = 8) by drinking water, or 1% cholesterol diet plus heme-L-lysinate (Heme group, n = 8) or ZnPP-IX (ZnPP group, n = 8) by injection in abdominal cavity for 10 weeks. RESULTS: Compared with those in control group, aortic NO production and expression of NOS decreased markedly; while CO production (P < 0.01) and HO-1 activity increased obviously in chol group. The aortic plaques area was (40.2 +/- 8.9)% in chol group. Compared with those in chol group, aortic areas [(26.6 +/- 9.2)%] reduced distinctly in heme group, aortic CO production and NOS activity increased obviously (P < 0.01) in L-arg group. However, compared with those in control group, HO-1 expression and CO production decreased markedly (P < 0.01) in heme group, while they were not different from those in chol group. Compared with those in chol group, aortic cNOS activity and NO production increased obviously and aortic plaques area [(28.1 +/- 7.7)%] greatly reduced (P < 0.01) in L-arg group. However, HO-1 expression and CO production of L-arg group decreased distinctly compared with those of control group, but they were similar to those of chol group. The aortic c-myc and c-fos expressions in both heme group and L-arg group reduced markedly compared with those in chol group, while they were similar to those in ZnPP and L-NAME group. CONCLUSION: The reciprocal relationship between heme oxygenase/carbon monoxide and nitric oxide synthase/nitrogen monoxide system in atherosclerosis may play the inhibitory role against atherosclerotic lesion.

Intracardiac basic fibroblast growth factor and transforming growth factor-beta 1 mRNA and their proteins expression level in patients with pressure or volume-overload right or left ventricular hypertrophy.

OBJECTIVES: The aim of the study was to investigate the pathogenic role of intracardiac basic fibroblast growth factor (bFGF) and transforming growth factor beta-1 (TGF beta-1) mRNA and their protein expression level in patients with ventricular volume or pressure-overload. BACKGROUND: Myocardial hypertrophy is responsiveness of cardiomyocytes and interstitial cells to ventricular stress produced by ventricular preload or/and afterload and a series of growth factors. However, the molecular mechanism by which the changes of bFGF and TGF beta-1 mRNA and their protein expression level in patients with volume or pressure-overload lead to distinct forms of cardiac hypertrophy is unclear. METHODS: 32 patients were divided into two groups: 16 patients with cardiac volume overload leading to left ventricular hypertrophy (VG) and 16 patients with pressure overload leading to right ventricular hypertrophy (PG), respectively, as compared with 5 unexpected deaths of noncardiac disease (CG), which is determinated by echocardiography and/or pathologic examination following operation; intracardiac bFGF and TGF beta-1 mRNA and their protein expression level were determined by immunohistochemistry and in situ hybridization as well as image analysis; cardiomyocytes and fibril collagen of type I and III were examined by haemotoxylin and eosin (HE) staining or sirius-red staining. RESULTS: Cardiocyte transverse diameter and fibril collagen of extracellular matrix, intracardiac bFGF and TGF beta-1 mRNA and their protein expression level in patients with volume or pressure-overload were significantly increased in both VG and PG, as compared with CG. CONCLUSION: This is the first paper to suggest that intracardiac bFGF and TGF beta-1 play a pivotal role in patients with pressure or volume-overload leading to right or left ventricular hypertrophy, composed of cardiomyocyte hypertrophy and extracellular matrix proliferation.

Apolipoprotein E gene polymorphisms and risk for coronary artery disease in Chinese Xinjiang Uygur and Han population.

OBJECTIVE: To examine the relationship between apolipoprotein E (Apo E) gene polymorphism and risk of coronary artery disease (CAD), analyzing association of polymorphism with classical risk factors. METHODS: A total of 124 patients (including 84 Han population and 40 Uygur population) with angiographically verified CAD or myocardial infarction were prospectively evaluated. Data referring to hypertension, diabetes, and tobacco consumption were recorded. The levels of total cholesterol (TC), high density lipoprotein (HDL) cholesterol, Apo A1 and B, and triglycerides (TG) were determined. DNA was obtained from 124 patients and 70 controls. In order to determine Apo E genotypes, DNA was PCR amplified and digested with HhaI. The genetic polymorphism of Apo E is due to three common alleles, epsilon (epsilon) 2, epsilon3, epsilon4, at a single autosomal gene locus. These alleles determine the six phenotypes E2/2, E3/3, E4/4, E4/2, E4/3, and E3/2. RESULTS: In Uygur population, the frequency of the epsilon2, epsilon3, and epsilon4 was 0.155, 0.648, and 0.197 respectively. In Han population, the frequency of the epsilon2, epsilon3, and epsilon4 was 0.081, 0.772, and 0.146 respectively. In the patient group, the frequency of the epsilon2, epsilon3, and epsilon4 was 0.060, 0.758, and 0.182 respectively. In the control group, the frequency of the epsilon2, epsilon3, and epsilon4 was 0.193, 0.671, and 0.136 respectively. epsilon2 frequency of Uygur' patients and controls was 0.050 and 0.290 respectively. Serum low density lipoprotein (LDL) cholesterol, TC, and TG values tended to decrease from the Apo E-4 phenotypes to Apo E-2 phenotypes. When deletion polymorphism of epsilon2 was compared with the common risk factors for CAD, its risk ratio (RR) is 4.38. CONCLUSIONS: These studies confirm and find that Apo E phenotype distribution in Uygur population differs significantly from that in Han population in Xinjiang. CAD patients have significantly lower epsilon2 allele and slightly higher epsilon3 or epsilon4 allele frequency than controls, especially in Uygur population. It shows protective effects of epsilon2 on CAD.

[Effects of dry red wine on experimental atherosclerosis in rabbits].

OBJECTIVE: To study the effects of dry red wine in the different stages of experimental atherosclerosis (AS) at the cell, molecular and gene regulation levels in order to provide scientific basis for using dry red wine in the prevention of atherosclerosis. METHODS: Blood vessel wall pathological changes, activity of NF-kB and the expressions of monocyte chemotactic protein-1 (MCP-1) and protein kinase C (PKC alpha) were observed in dietary induced atherosclerosis rabbit model by morphology study, electrophoretic mobility shift assay (EMSA), and in situ hybridyzation, and the effects of dry red wine intervention were examined. RESULTS: Dry red wine significantly suppressed the proliferation of atherosclerosis intima and NF-kappaB activation (4w: 18.5 +/- 0.6 vs 13.7 +/- 0.3; 8w: 26 +/- 0.9 vs 17.8 +/- 0.5; 12w: 39.9 +/- 1.2 vs 27.8 +/- 0.8), and down-regulated the expressions of MCP-1 and PKC alpha. CONCLUSIONS: The results confirmed that dry red wine could protect AS tissues and prolong its development by suppressing NF-kappaB activation, down-regulating the expressions of MCP-1 and PKC alpha, which may take part in pathogenesis of AS.

[The roles of nuclear Ca2+/CaM dependent kinases and calcineurin on the development of myocardial hypertrophy in rat].

AIM: To evaluate whether protein phosphorylation and dephosphorylation in nuclei play roles in the development of myocardial hypertrophy, distribution of protein kinases and phosphatases in cell fractions were determined. METHODS: The model of hypertensive rat was established by abdominal aortic constriction. Velocity and isopyknic gradient centrifugation was employed to fractionate rat myocardium to membrane, cytosol and nuclei. Enzymatic methods were employed to determine kinases and phosphatases. RESULTS: Compare with control group, the activity of CaMK increased by 101.1% (P < 0.01) and 40.16% (P < 0.01) respectively in nuclear and membranous fractions, changed without significance in cytosolic fraction; the activity of calcineurin in nuclei increased by 43.57%, (P < 0.05), lightly changed without significance in membranous and cytosolic fractions. CONCLUSION: Nuclear translocation of CaMK and calcineurin, might play important roles on overload-induced cardiac hypertrophy.

[Effects of insulin on the distribution of actins in vascular smooth muscle cells in the process of proliferation via mitogen-activated protein kinase in vitro].

Proliferation of vascular smooth muscle cells (VSMCs) is often accompanied by changes in intracellular actin distribution. The changes are controlled by the signal transduction pathways of protein kinase C/mitogenic activated protein kinase (PKC-MAPK), but the mechanism is unclear. In order to study the effect of insulin on the intracellular signal transduction (PKC-MAPK) probably involved in the modulation of proliferation and redistribution of actins in the VSMCs, the DNA synthesis, MAPK activities and its gene expression, and the redistribution of intracellular actins were investigated in the isolated VSMCs of SHR pretreated with PKC inhibitor and/or insulin, respectively. We found that insulin treatment resulted in proliferation of the VSMCs and an increase in [(3)H] TdR incorporation. Meanwhile, the activities and expression of MAPK increased significantly compared to the control group. These effects of insulin were blocked by PKC inhibitor. In addition, insulin caused a redistribution of the intracellular actins in VSMCs, which was also inhibited by PKC inhibitor. It is, therefore, suggested that these effects of insulin on VSMCs proliferation and distribution of the intracellular actins may be mediated by the MAPK signal transduction pathway.

[Investigation of nuclear Ca2+ regulation in the isolated cardiac nuclei].

To investigate the regulation of Ca2+ in the isolated cardiac nuclei from rats which may illuminated the mechanism of nuclear calcium transport system. Elocity and isopyknic gradient centrifugation were employed to fractionate rat cardiac nuclei. Then fluo-4 confocal microscopy techniques was used to verify the changes of nuclear Ca2+. There are calcium-dependent Ca2+ uptake in the cardiac nuclear obtained from normal rats. The accumulation Ca2+ of cardiac nuclei in vitro from the incubating medium were not consistent with free [Ca2+] in incubating medium. The nuclear envelope was initially loaded with Ca2+ (1 mmol/L ATP and approximately 100 nmol/L Ca2+), Adequate Ca2+ loading was next confirmed by imaging the nuclear envelope and nucleoplasm. Exposure of Ca2+ -loaded nuclei to IP3, ryanodine or ryanodine + thapsigargin, respectively, resulted in a rapid and transient elevation of nucleoplasmic Ca2+ free concentration, this effects were abolished by pretreatment of cardiac nuclei with Ca2+ -ATPase inhibitor thapsigargin. Thapsigargin and IP3 receptor antagonist heparin induced nucleoplasmic Ca2+ free concentration decrease. Fluorescence experiments indicated that both ryanodine receptors and Ca2+ -ATPase were distributed in the outer layer of nuclear envelope, and inositol 1,4,5-trisphosphate receptors mainly dispersively localized at inner layer of nuclear envelope. The present study demonstrates that nuclear calcium were regulated by free Ca2+, IP3 and ryanodine. The results suggested calcium transport system might be present in the myocardial nuclei, the myocardial nuclei might served as one of calcium pools in myocardial cell.