Carnosine protects neurons against oxidative stress and modulates the time profile of MAPK cascade signaling.

Carnosine is a known protector of neuronal cells against oxidative injury which prevents both apoptotic and necrotic cellular death. It was shown earlier that carnosine serves as an intracellular buffer of free radicals. Using the model of ligand-dependent oxidative stress in neurons, we have shown that homocysteine (HC) initiates long-term activation of extracellular signal regulated kinase, isoforms 1 and 2 (ERK 1/2) and Jun N-terminal kinase (JNK) which corresponds to exitotoxic effect resulting in cellular death.

Sodium pump alpha1 and alpha3 subunit isoforms mediate distinct responses to ouabain and are both essential for survival of human neuroblastoma.

Using SK-N-AS human neuroblastoma cells, which co-express the alpha1 and alpha3 isoforms of the sodium pump alpha subunit, we selectively silenced either the alpha1 or alpha3 subunit by means of transfection with small interfering RNA, and investigated cell survival and the cellular response to ouabain. We found that both of the alpha subunits are essential for cell survival, indicating that substitution of one subunit for the other is not sufficient. In the presence of both alpha subunits, ouabain causes sustained activation of extracellular signal-regulated kinases 1 and 2 (Erk1/2).

Different neuronal Na(+)/K(+)-ATPase isoforms are involved in diverse signaling pathways.

Inhibition of rat neuronal Na(+)/K(+)-ATPase alpha3 isoform at low (100 nM) ouabain concentration led to activation of MAP kinase cascade via PKC and PIP(3) kinase. In contrast to ouabain-sensitive alpha3 isoform of Na(+)/K(+)-ATPase, an ouabain-resistant alpha1 isoform (inhibition with 1 mM of ouabain) of Na(+)/K(+)-ATPase regulates MAP kinase via Src kinase dependent reactions. Using of Annexin V-FITC apoptotic test to determine the cells with early apoptotic features allows to conclude that alpha3 isoform stimulates and alpha1 suppresses apoptotic process in cerebellum neurons.