The mechanism of delayed rectifier potassium channel regulated by cyclooxygenase -2 in gastric cancer cells / 中华消化杂志

ABSTRACT

Objective To investigate the currents impact on delayed rectifier potassium (HERG)regulated by cyclooxygenase (COX)-2 in gastric cancer cells and its mechnism. Methods ① The HERG mRNA, protein and current in gastric cancer cells transfected with or without COX-2 antisense vector were measured by RT-PCR, Western blot and patch-clamp, respectively. ② cAMP concentration in gastric cancer cells transfected with or without COX-2 antisense vector was measured by ELISA. ③ The mutant HERG, which was absence of cAMP-binding domain, was constructed by PCR and transfected into gastric cancer cells. ④ The impact of COX-2 inhibitor and proglandin (PG) E2 on HERG current in gastric cancer cells transfected with or without mutant HERG was investigated by patch clamp. ⑤ The effects of agonist and antagonist of cAMP and inhibitor of protein kinase (PK) A on HERG current in gastric cancer cells transfected with or without HERG mutant were observed by patch clamp. Results ① The expression of HERG mRNA and protein in gastric cancer cells transfected with COX-2 antisense vector were not altered, but the amplitude of HERG current was diminished (P<0.05). ② The cAMP concentration in gastric cancer cells transfected with COX-2 antisense vector was lower than that in parental gastric cancer cells (P<0.05). ③ COX-2 inhibitor and PGE2 had influence on the HERG currents in gastric cancer cells. COX-2 inhibitor reduced and PGE2 enhanced the amplitude of HERG current in gastric cancer cells. However, neither COX-2 inhibitor nor PGE2 showed any negative or positive effects on currents of mutant HERG. ④ cAMP agonist enhanced the amplitude of HERG current and cAMP antagonist reduced the amplitude in gastric cancer cells. Neither agonist nor antagonist had effect on currents of mutant HERG. ⑤ PKA inhibitor did not influence the HERG current of parental gastric cancer cells and gastric cancer cells transfected with mutant. Conclusions COX-2 regulates HERG current through its catalytic product of PGE2, which binds with its receptor on the gastric cancer cells and alters cAMP level in gastric cancer cells, cAMP interacts with HERG protein by binding with cAMP-binding domain of HERG protein and exerts impact on HERG current. PKA does not participate in this process.