Protective effects of fractions from Pseudostellaria heterophylla against cobalt chloride-induced hypoxic injury in H9c2 cell.

Except for as a well-known tonic Chinese herbal medicine for the treatment of splenic asthenia, anorexia, lassitude and weakness, the roots of Pseudostellaria heterophylla was also used in Chinese medicines for the treatment of palpitation.The study was designed to determine whether fractions from Pseudostellaria heterophylla could provide cardioprotection on hypoxic cardiomyocytes, what structural types of compounds were responsible for the observed effects, and which is the possible mechanism of action.The roots of Pseudostellaria heterophylla were extracted successively with 70% aqueous ethanol and water to give a 70% ethanol extract and a water extract. The latter was first precipitated by 80% ethanol and then protein-removed by the Sevag method to give a fraction enriched in polysaccarides (PHP). The former was separated by column chromatography into a fraction enriched in small-molecule sugars and amino acids (PHSSAC), saponins (PHS), cyclopeptides (PHCP), and sapogenins (PHSG). UV spectral or chemical methods were used to confirm the five fractions. The cardioprotective effects of the fractions were evaluated by measuring the viability and the leakage of lactate dehydrogenase (LDH) of the fraction-pretreated cardiomyocyte H9c2 after exposure to CoCl2-induced hypoxia. The mechanism of action was studied by investigating the nature of cell death inhibition (by Annexin V/PI flow cytometric analysis) and their effects on the levels of malonaldehyde (MDA), superoxide dismutase (SOD) and intracellular reactive oxygen species (ROS).Fractions PHS and PHP could attenuate CoCl2-induced hypoxic damage to an extent higher than or comparable to the effect of the positive control N-acetyl-l-cysteine (NAC). Pretreatment of the cells with 800 μg/mL of PHS or 10mg/mL of PHP markedly decreased the level of MDA, reduced intracellular ROS, increased the activity of SOD, and reduced leakage of LDH to the levels close to or better than that with 326 μg/mL of NAC. Reduction of apoptosis was also observed for both fractions.The overall results suggested that the traditional use of this plant for the treatment of palpitation may be attributed to the presence of cardioprotective agents in Pseudostellaria heterophylla. PHP and PHS were the two active fractions responsible for its cardioprotective effect. The mechanism might involve protections of the cell membrane from hypoxic damage and of the cells from oxidative injury via preventing increased oxidative stress. Protection of the cells via inhibition of cellular apoptosis may also be involved.