Salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline; Sal) is structurally similar to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, which is supposed to have a role in the development of Parkinson-like syndrome in both human and non-human subjects. In the human brain, the amount of (R)-enantiomer of Sal is much higher than (S )-enantiomer, suggesting that a putative enzyme may participate in the synthesis of (R)-salsolinol, called (R)-salsolinol synthase. In this study, the (R)-salsolinol synthase activity in the condensation of dopamine and acetaldehyde was investigated in the crude extracts from the brains of Sprague Dawley rats. Identification of the enzymatic reaction products and enzyme activity detection were achieved by HPLC-electrochemical detection. The discovery of this enzyme activity in rat's brain indicates the natural existence of (R)-salsolinol synthase in the brains of humans and rats, and it is distributed in most brain regions of rat with higher activity in soluble proteins extracted from striatum and substantia nigra.

Recent studies have evaluated the role of direct radiation exposure in neurodegenerative disorders; however, association among indirect effects of radiation and neurodegenerative diseases remains rarely discussed. The objective of this study was to estimate the relative risk of neurodegeneration due to direct and indirect effects of radiation. (60)Co gamma ray was used as source of direct radiation whereas irradiated cell conditioned medium (ICCM) was used to mimic the indirect effect of radiation. To determine the potency of ICCM to inhibit neuronal cells survival colony forming assay was performed. The role of ICCM to induce apoptosis in neuronal SH-SY5Y cells was estimated by TUNEL assay and Annexin V/PI assay. Level of oxidative stress and the concentration of inflammatory cytokines after exposing to direct radiation and ICCM were evaluated by ELISA method. Expression of key apoptotic protein following direct and indirect radiation exposure was investigated by western blot technique. Experimental data manifest that ICCM account loss of cell survival and increase apoptotic induction in neuronal SH-SY5Y cells that was dependent on time and dose. Moreover, ICCM stimulate significant release of inflammatory cytokines i.e., tumor necrosis factor TNF-alpha (P < 0.01), Interleukin-1 (IL-1, P < 0.001), and Interleukin-6 (IL-6, P < 0.001) in neuronal SH-SY5Y cells and elevate the level of oxidative stress (MDA, P < 0.01). Up-regulation of key apoptotic protein expression i.e., Bax, Bid, cytochrome C, caspase-8 and caspase-3 confirms the toxicity of ICCM to neuronal cells. This study provides the evidence that indirect effect of radiation can be as much damaging to neuronal cells as direct radiation exposure can be. Hence, more focused research on estimation risks of indirect effect of radiation to CNS at molecular level may help to reduce the uncertainty about cure and cause of several neurodegenerative disorders.

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