RESUMO
Reactive oxygen species (ROS)-induced oxidative stress triggers the vicious cycle leading to the degeneration of dopaminergic neurons in the nigra pars compacta. ROS produced during the metabolism of dopamine is immediately neutralized by the endogenous antioxidant defense system (EADS) under physiological conditions. Aging decreases the vigilance of EADS and makes the dopaminergic neurons more vulnerable to oxidative stress. As a result, ROS left over by EADS oxidize the dopamine-derived catechols and produces a number of reactive dopamine quinones, which are precursors to endogenous neurotoxins. In addition, ROS causes lipid peroxidation, uncoupling of the electron transport chain, and DNA damage, which lead to mitochondrial dysfunction, lysosomal dysfunction, and synaptic dysfunction. The mutations in genes such as DNAJC6, SYNJ1, SH3GL2, LRRK2, PRKN, and VPS35 caused by ROS have been associated with synaptic dysfunction and the pathogenesis of Parkinson's disease (PD). The available drugs that are used against PD can only delay the progression of the disease, but they produce various side effects. Through their antioxidant activity, flavonoids can substantiate the EADS of dopaminergic neurons and disrupt the vicious cycle incepted by oxidative stress. In this review, we show how the oxidative metabolism of dopamine generates ROS and dopamine-quinones, which then exert unrestrained OS, causing mutations in several genes involved in the proper functioning of mitochondrion, synapse, and lysosome. Besides, we also present some examples of approved drugs used for the treatment of PD, therapies in the clinical trial phase, and an update on the flavonoids that have been tested to boost the EADS of dopaminergic neurons.
RESUMO
Diabetes mellitus is a syndrome and an endocrine disorder, primarily considered as a loss of glucose homeostasis because of the insulin action and/or secretion or both. Currently there are more than 150 million people in the world affected by diabetes mellitus with a higher share of Asian and European countries. The current study aimed to investigate the comparative altering properties of streptozotocin (STZ), based on up-turn and down-turn configuration of biochemical, toxicological and hematological parameters in comparison with normoglycemic male albino rats. This comparative study was conducted among normoglycemic and STZ based induced-type 2 diabetic male albino rats groups. The male albino rats were intra-peritoneally injected with STZ with the dose rate of 65 mg/kg body weight for one time to developed type 2 diabetic model. Biochemical (blood glucose, uric acid, urea and creatinine), toxicological (AST, ALT and ALP) and hematological parameters (red and white blood cells) and their functional indices were evaluated in type 2 diabetic induced group along with normoglycemic rats. The STZ based induced- type 2 diabetic rats showed statistically significance (p < 0.001) higher level in the blood glucose, alongwith the change in the levels of biochemical parameters including urea, uric acid, and creatinine. Toxicological parameters comprising AST, ALT and ALP were also shown significance (p < 0.001) as sufficient after experimental evaluation of biologically important parameter in STZ based induced-type 2 diabetic rats. Likewise, the red blood cells, white blood cells and their efficient components were exposed significantly insufficient after the injecting of STZ to induce the rats as type 2 diabetic. The results of the current study indicates the comparatively higher levels of variation among biochemical, toxicological and hematological parameters in STZ based Induced-type 2 diabetic model as compared to normoglycemic group.