Hydrogen gas protects against serum and glucose deprivation­induced myocardial injury in H9c2 cells through activation of the NF­E2­related factor 2/heme oxygenase 1 signaling pathway.

Ischemia or hypoxia­induced myocardial injury is closely associated with oxidative stress. Scavenging free radicals and/or enhancing endogenous antioxidative defense systems may be beneficial for the impediment of myocardial ischemic injury. Hydrogen (H2) gas, as a water­ and lipid­soluble small molecule, is not only able to selectively eliminate hydroxyl (·OH) free radicals, but also to enhance endogenous antioxidative defense systems in rat lungs and arabidopsis plants. However, thus far, it has remained elusive whether H2 gas protects cardiomyocytes through enhancement of endogenous antioxidative defense systems. In the present study, the cardioprotective effect of H2 gas against ischemic or hypoxic injury was investigated, along with the underlying molecular mechanisms. H9c2 cardiomyoblasts (H9c2 cells) were treated in vitro with a chemical hypoxia inducer, cobalt chloride (CoCl2), to imitate hypoxia, or by serum and glucose deprivation (SGD) to imitate ischemia. Cell viability and intracellular ·OH free radicals were assessed. The role of an endogenous antioxidative defense system, the NF­E2­related factor 2 (Nrf2)/heme oxygenase 1 (HO­1) signaling pathway, was evaluated. The findings revealed that treatment with CoCl2 or SGD markedly reduced cell viability in H9c2 cells. H2 gas­rich medium protected against cell injury induced by SGD, but not that induced by CoCl2. When the cells were exposed to SGD, levels of intracellular ·OH free radicals were markedly increased; this was mitigated by H2 gas­rich medium. Exposure of the cells to SGD also resulted in significant increases in HO­1 expression and nuclear Nrf2 levels, and the HO­1 inhibitor ZnPP IX and the Nrf2 inhibitor brusatol aggravated SGD­induced cellular injury. H2 gas­rich medium enhanced SGD­induced upregulation of HO­1 and Nrf2, and the HO­1 or Nrf2 inhibition partially suppressed H2 gas­induced cardioprotection. Furthermore, following genetic silencing of Nrf2 by RNA interference, the effects of H2 gas on the induction of HO­1 and cardioprotection were markedly reduced. In conclusion, H2 gas protected cardiomyocytes from ischemia­induced myocardial injury through elimination of ·OH free radicals and also through activation of the Nrf2/HO­1 signaling pathway.

Improvement in cardiac function after bone marrow cell thearpy is associated with an increase in myocardial inflammation.

The mechanisms for the beneficial impact of bone marrow cell (BMC) therapy after myocardial infarction (MI) are ill defined. We hypothesized that the implanted cells improve function by attenuating post-MI inflammation and repair. In mice, 3 x 10(5) fresh BMCs were implanted immediately after coronary ligation. Cardiac function was evaluated over time. Inflammatory cytokines and cells were measured, and their impacts on the (myo)fibroblastic repair response, angiogenesis, and scar formation were determined. All differences below had P values of <0.05. BMC implantation reduced the decline in fractional shortening and ventricular dilation. Invasive hemodynamics confirmed a difference in systolic function at day 7 and diastolic function at day 28 favoring the BMC group. Interestingly, BMC implantation caused a 1.6-fold increase in the number of macrophages infiltrating the infarct but did not affect neutrophils. This increase was associated with a 1.9-fold higher myocardial TNF-alpha level. The heightened inflammatory response was associated with a 1.4-fold induction of transforming growth factor-beta and a 1.3-fold induction of basic fibroblast growth factor. These changes resulted in a 1.6-fold increase in alpha-smooth muscle actin and a 1.9-fold increase in total discoidin domain receptor 2-expressing cells in the BMC group. These two markers are expressed by cardiac (myo)fibroblasts. Capillary density in the border zone increased 2.0-fold. Consistent with a more robust repair-mediated scar "contracture," the final scar size was 0.7-fold smaller in the BMC group. In conclusion, after MI, BMC therapy induced a more robust inflammatory response that improved the "priming" of the (myo)fibroblast repair phase. Enhancing this response may further improve the beneficial impact of cellular therapy.