[Expression of heme oxygenase-1 in neonatal rat cardiocytes induced by lipopolysaccharide]

To study the alterations of heme oxygenase-1 mRNA in neonatal rat cardiomyocytes (NRCMs) induced by lipopolysaccharide (LPS) and the role of heme oxygenase-1 (HO-1) in the LPS induced disorders of myocardium function, 10 (L, 6 h), 30 (M, 6 h), 50 micrograms/ml (H, 6 h) LPS and 10 micrograms/ml LPS + 10 mumol/ml Zn-protoporphyrin-IX (ZnPPIX; L + I, 6 h) and 10 mumol/ml ZnPPIX alone (I, 6 h) were added to the medium for a 6-hour culture of NRCMs, and 10 micrograms/ml LPS for 9 h (L, 9 h) and 18 h (L, 18 h) cultures. LDH release and MDA contents of the cells were measured. When NRCMs were collected, Trypan blue stain method was used to examine the mortality (the rate of Trypan blue uptake) of NRCMs. HO-1 mRNA expression was examined by Northern blot. The results showed that HO-1 mRNA expression of NRCMs increased gradually along with the increase of LPS concentration below the level of 30 micrograms/ml. When the final concentrations of LPS were 10 and 30 micrograms/ml, the HO-1 mRNA expression of NRCMs increased by 81.2% and 126.3% respectively compared with control. When the final concentration of LPS was 50 micrograms/ml, the HO-1 mRNA expression decreased to the level of 10 micrograms/ml group. When the final concentration was 10 micrograms/ml, the HO-1 mRNA expression increased gradually along with the culture time. After a 9- or 18-hour culture, the HO-1 mRNA expression of NRCMs increased by 93.6% and 105.8% respectively compared with control. Only when NRCMs had been cultured with 30, 50 micrograms/ml LPS and 10 micrograms/ml LPS + 10 mumol/ml ZnPPIX for 6 h and 10 micrograms/ml LPS for 18 h, the rate of Trypan blue stain uptake, MDA contents and LDH release significantly increased. With 10 micrograms/ml LPS alone and 10 mumol/ml ZnPPIX alone for 6 h, the above parameters were not significantly increased (P > 0.05). The results demonstrate that LPS induces HO-1 mRNA expression of NRCMs dose- and time-dependently to some extent. The inducible HO can protect NRCMs from injury and thus play an important role in pathogenesis of myocardium under LPS.