Hydrogen Sulfide Restored the Diurnal Variation in Cardiac Function of Aging Mice.

The present study was performed to investigate whether HS could restore the diurnal variation in cardiac function of aging mice and explore the potential mechanisms. We found that ejection fraction (EF) and fractional shortening (FS) in 3-month-old mice exhibited diurnal variations over a 24-hour period. However, the diurnal variations were disrupted in 18-month-old mice, and there was a decline in EF and FS. In addition, the plasma malondialdehyde (MDA) levels were increased, and HS concentrations and superoxide dismutase (SOD) activities were decreased in 18-month-old mice. Then, CSE KO mice were used to determine if there was a relationship between endogenous HS and diurnal variations in EF and FS. There was no difference in 12-hour averaged EF and FS between dark and light periods in CSE KO mice accompanying increased MDA levels and decreased SOD activities in plasma, indicating that deficiency of endogenous HS blunted diurnal variations of cardiac function. To determine whether oxidative stress disrupted the diurnal variations in cardiac function, D-galactose-induced subacute aging mice were employed. After 3-month D-gal treatment, both 12-hour averaged EF and FS in dark or light periods were decreased; meanwhile, there was no difference in 12-hour averaged EF and FS between dark and light periods. After 3-month NaHS treatment in the D-gal group, the plasma MDA levels were decreased and SOD activities were increased. The EF and FS were lower during the 12-hour light period than those during the 12-hour dark period which was fit to sine curves in the D-gal+NaHS group. Identical findings were also observed in 18-month-old mice. In conclusion, our studies revealed that the disrupted diurnal variation in cardiac function was associated with increased oxidative stress and decreased HS levels in aging mice. HS could restore the diurnal variation in cardiac function of aging mice by reducing oxidative stress.