Autophagy is necessary for neuronal homeostasis and its dysfunction has been implicated in Parkinson's disease (PD) as it can exacerbate endoplasmic reticulum (ER) stress and ER stress-induced apoptosis. Quercetin is a flavonoid known for its neuroprotective and antioxidant effects. The present study investigated the protective, autophagy-modulating effects of quercetin in the rotenone rat model of PD. Rotenone was intraperitoneally injected at dose of 2 ml/kg/day for 4 weeks. Simultaneous intraperitoneal injection of quercetin was given at a dose of 50 mg/kg/day also for 4 weeks. Neurobehavioral changes were studied. Oxidative/antioxidant status, C/EBP homologous protein (CHOP), Beclin-1, and dopamine levels were assessed. DNA fragmentation and histopathological changes were evaluated. This research work revealed that quercetin significantly attenuated rotenone-induced behavioral impairment, augmented autophagy, ameliorated ER stress- induced apoptosis with attenuated oxidative stress. From the current study, quercetin can act as an autophagy enhancer in PD rat model and modulates the microenvironment that leads to neuronal death.
Geraniol (GE), an important ingredient in several essential oils, displayed pleiotropic biological activities through targeting multiple signaling cascades. In the current study, we aimed to examine the protective effect of GE on d-galactose (d-gal) induced cognitive impairment and explore the underlying mechanisms. Forty male Wistar rats (8 weeks old) were randomly categorized into 4 groups; Group I (saline + vehicle [edible oil]), group II (saline + geraniol) (100 mg/kg/day orally), group III (d-galactose) (100 mg/kg/day subcutaneously injected), and group IV (d-galactose + geraniol). Behavioral impairments were evaluated. Brain levels of malondialdehyde (MDA) and reduced glutathione (GSH) as well as superoxide dismutase (SOD) and acetylcholinesterase (AchE) activities were estimated. The levels of inflammatory markers [tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, IL-6, and nuclear factor kappa beta (NF-kβ)], endoplasmic reticulum stress sensors [inositol requiring protein 1(IRE1) and protein kinase RNA–like endoplasmic reticulum kinase (PERK)], brain-derived neurotrophic factor (BDNF), and mitogen-activated protein kinases (MAPK) pathway were measured by ELISA. Also, hippocampal histopathological assessment and immunohistochemical analysis of glial fibrillary acidic protein (GFAP) and caspase-3 were performed. Glucose regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) mRNA expression and protein levels were assessed. GE effectively ameliorated aging-related memory impairment through increasing GSH, BDNF, Ach levels, and SOD activity. Additionally, GE treatment caused a decrease in the levels of MDA, inflammatory mediators, and ER stress sensors as well as the AchE activity together with concomitant down-regulation of GRP78 and CHOP mRNA expression. Moreover, GE improved neuronal architecture and rat's spatial memory; this is evidenced by the shortened escape latency and increased platform crossing number. Therefore, GE offers a unique pharmacological approach for aging-associated neurodegenerative disorders.
Graphical Abstract
Diabetic nephropathy (DN) is one of the most common microvascular diabetic complications. This study was designed to evaluate the possible protective effect and underlying mechanisms of HO-1 induction in streptozotocin (STZ)-induced early DN in rats. The diabetic rats were divided into three groups: STZ-diabetic, cobalt protoporphyrin (CoPP)-treated diabetic, and zinc protoporphyrin IX (ZnPP)-treated diabetic groups. Compared to the STZdiabetic group, CoPP-induced HO-1 upregulation improved the diabetic state and renal functional parameters, suppressed the renal proinflammatory marker, NF-κB, abrogated the elevated renal hydroxyprolin, and decreased the enhanced renal nicotinamide adenine dinucleotide phosphate oxidase activity with parallel reduction of urinary oxidative stress markers. On the contrary, treatment with ZnPP abrogated HO-1 levels, aggravated the diabetic condition with further increases in renal oxidative stress, fibrotic and inflammatory markers, and exacerbated renal dysfunction in diabetic animals. These findings suggest that the reduced diabetic renal injury upon HO-1 induction implicates the role of HO-1 induction as a potential treatment for DN.
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