Inhibition of ATP-induced calcium influx in HT4 cells by glucocorticoids:involvement of protein kinase A  

作　　者：Jian-zhongHAN WenLIN Yi-zhangCHEN 

机构地区：[1]NeuroscienceResearchInstitute.andDepartmentofNeurobiology [2]DepartmentofPharmacology,CollegeofPharmacy,SecondMilitaryMedicalUniversity,Shanghai200433,China

出　　处：《Acta Pharmacologica Sinica》2005年第2期199-204,共6页中国药理学报（英文版）

基　　金：Project supported by the National Basic Research Program of China(№ G1999054003);the National Natural Science Foundation of China(№ 39330100 and 39840019)

摘　　要：Aim:In our previous observations,adenosine triphosphate(ATP)was found to evoke immediate elevations in intracellular free calcium concentration([Ca^(2+)]_i) in HT4 neuroblastoma cells of mice.We tried to see if a brief pretreatment of glucocorticoids could inhibit the Ca^(2+)response and reveal the underlying signal- ing mechanism.Methods:Measurement of[Ca^(2+)]_i was carried out using the dual-wavelength fluorescence method with Fura-2 as the indicator.Results:Pre- incubation of HT4 cells for 5 min with corticosterone(B)or bovine serum albu- min conjugated corticosterone(B-BSA)inhibited the peak[Ca^(2+)]_i increments in a concentration-dependent manner.Cortisol and dexamethasone had a similar action, while deoxycorticosterone and cholesterol were ineffective.Both extracellular Ca^(2+)influx and intemal Ca^(2+)release contributed to ATP-induced[Ca^(2+)]_i elevation. The brief treatment with only B attenuated Ca^(2+)influx.Furthermore,the[Ca^(2+)]_i elevation induced by the P2X receptor agonist adenosine 5'-(β,γ-methylene)triph- osphate(β,γ-meATP)was also suppressed.The rapid inhibitory effect of B can be reproduced by forskolin 1 mmol/L and blocked by H89 20 mmol/L.Neither nuclear glucocorticoid receptor antagonist mifepristone nor protein kinase C in- hibitors influenced the rapid action of B.Conclusion:Our results suggest that glucocorticoids modulate P2X receptor-medicated Ca^(2+)influx through a mem- brane-initiated,non-genomic and PKA-dependent pathway in HT4 cells.Aim:In our previous observations,adenosine triphosphate(ATP)was found to evoke immediate elevations in intracellular free calcium concentration([Ca^(2+)]_i) in HT4 neuroblastoma cells of mice.We tried to see if a brief pretreatment of glucocorticoids could inhibit the Ca^(2+)response and reveal the underlying signal- ing mechanism.Methods:Measurement of[Ca^(2+)]_i was carried out using the dual-wavelength fluorescence method with Fura-2 as the indicator.Results:Pre- incubation of HT4 cells for 5 min with corticosterone(B)or bovine serum albu- min conjugated corticosterone(B-BSA)inhibited the peak[Ca^(2+)]_i increments in a concentration-dependent manner.Cortisol and dexamethasone had a similar action, while deoxycorticosterone and cholesterol were ineffective.Both extracellular Ca^(2+)influx and intemal Ca^(2+)release contributed to ATP-induced[Ca^(2+)]_i elevation. The brief treatment with only B attenuated Ca^(2+)influx.Furthermore,the[Ca^(2+)]_i elevation induced by the P2X receptor agonist adenosine 5'-(β,γ-methylene)triph- osphate(β,γ-meATP)was also suppressed.The rapid inhibitory effect of B can be reproduced by forskolin 1 mmol/L and blocked by H89 20 mmol/L.Neither nuclear glucocorticoid receptor antagonist mifepristone nor protein kinase C in- hibitors influenced the rapid action of B.Conclusion:Our results suggest that glucocorticoids modulate P2X receptor-medicated Ca^(2+)influx through a mem- brane-initiated,non-genomic and PKA-dependent pathway in HT4 cells.

关 键 词：CALCIUM GLUCOCORTICOIDS adenosine triphosphate protein kinase C protein kinase A 

分 类 号：R977.1[医药卫生—药品]