Shenxian Shengmai Oral Liquid Modulates Ca²⁺/CaM-CaMKⅡ Pathway To Delay Sinus Node Fibrosis

Purpose:To explore whether Shenxian Shengmai Oral Liquid can reduce the fibrosis of sinus node tissue in mice with sick sinus syndrome by inhibiting calcium overload of sinus node cells,thereby improving sinus node function,and to explore whether its mechanism is related to Ca²⁺/Ca M-Ca MKII pathway related.Material and method:SPF grade C57BL/6 mice were randomly divided into 3 groups by random number table method:sham operation group（SHAM）,sick sinus syndrome model group（SSS）,Shenxian Shengmai oral liquid treatment group（SXSM）,each group 10 mice;micro-osmotic pumps were placed subcutaneously in each group of mice,and the SSS group and SXSM group were continuously pumped with Angiotensin II to induce chronic sinus node damage to simulate sick sinus syndrome,and the SHAM group was pumped Into normal saline;The mice in the SXSM group were given intragastric administration of Shenxian Shengmai oral liquid 15ml/kg/d on the next day of modeling,and the other two groups were intragastrically infused with corresponding doses of normal saline every day;mice in each group were treated separately before modeling（I.e.0d）,7d,14d,21d and 28d after modeling,regularly monitor the changes of heart rate;take samples after 28 days,use HE staining and MASSON staining to observe the histological changes and fibrosis degree of the sinoatrial node in mice;laser scanning Confocal microscope was used to detect the changes of Ca²⁺content in mouse sinoatrial node cells;Western-blot method was used to detect Ca²⁺/Ca M-Ca MKII pathway related proteins,matrix metalloproteinase 2（MMP-2）,fibrosis-related factor type I collagenα1 chain（COL1A1）,voltage-gated calcium channel L-type（Cav1.2,Cav1.3）and T-type（Cav3.1）protein expression;q RT-PCR method to detect the sinoatrial node tissue Ry R2,SERCA2a,Cav1.2,Cav1.3,Cav3.1 m RNA levels of each group of mice.Results:1.Heart rate:Shenxian Shengmai oral liquid significantly increased the heart rate of SSS mice（P<0.05）.2.Histological changes:Shenxian Shengmai Oral Liquid significantly improved the pathological changes and fibrosis of sinoatrial node tissue in SSS mice.3.Ca²⁺content change:Shenxian Shengmai Oral Liquid reduced the Ca²⁺concentration in the sinoatrial node area of SSS mice（P<0.05）.4.Western-blot detection:Shenxian Shengmai Oral Liquid significantly down-regulated the expression of Ca²⁺/Ca M-Ca MKII pathway related proteins and MMP-2,COL1A1,Ry R2,Cav1.2,Cav1.3,Cav3.1 protein,and up-regulated SERCA2a protein The expression of（P<0.05）.5.q RT-PCR detection:Shenxian Shengmai Oral Liquid down-regulated the levels of Ry R2,Cav1.2,Cav1.3,Cav3.1 m RNA,and up-regulated the level of SERCA2a m RNA（P<0.05）.Conclusion:1.Shenxian Shengmai Oral Liquid can significantly reduce the sinus node damage induced by angiotensin II and improve the function of the sinus node.2.Shenxian Shengmai Oral Liquid improves sinus node fibrosis in SSS mice and inhibits calcium overload of sinus node cells.3.The protective effect of Shenxian Shengmai oral liquid on sinoatrial node may be related to its ability to inhibit Ca²⁺/Ca M-Ca MKII signal pathway and reduce pathological calcium influx in sinoatrial node cells.