Polyphenolic Extract of Euphorbia supina Attenuates Manganese-Induced Neurotoxicity by Enhancing Antioxidant Activity through Regulation of ER Stress and ER Stress-Mediated Apoptosis

Abstract

Manganese (Mn) is an important trace element present in human body, which acts as an enzyme co-factor or activator in various metabolic reactions. While essential in trace amounts, excess levels of Mn in human brain can produce neurotoxicity, including idiopathic Parkinson’s disease (PD)-like extrapyramidal manganism symptoms. This study aimed to investigate the protective role of polyphenolic extract of Euphorbia supina (PPEES) on Mn-induced neurotoxicity and the underlying mechanism in human neuroblastoma SKNMC cells and Sprague-Dawley (SD) male rat brain. PPEES possessed significant amount of total phenolic and flavonoid contents. PPEES also showed significant antioxidant activity in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and reducing power capacity (RPC) assays. Our results showed that Mn treatment significantly reduced cell viability and increased lactate dehydrogenase (LDH) level, which was attenuated by PPEES pretreatment at 100 and 200 µg/mL. Additionally, PPEES pretreatment markedly attenuated Mn-induced antioxidant status alteration by resolving the ROS, MDA and GSH levels and SOD and CAT activities. PPEES pretreatment also significantly attenuated Mn-induced mitochondrial membrane potential (ΔΨm) and apoptosis. Meanwhile, PPEES pretreatment significantly reversed the Mn-induced alteration in the GRP78, GADD34, XBP-1, CHOP, Bcl-2, Bax and caspase-3 activities. Furthermore, administration of PPEES (100 and 200 mg/kg) to Mn exposed rats showed improvement of histopathological alteration in comparison to Mn-treated rats. Moreover, administration of PPEES to Mn exposed rats showed significant reduction of 8-OHdG and Bax immunoreactivity. The results suggest that PPEES treatment reduces Mn-induced oxidative stress and neuronal cell loss in SKNMC cells and in the rat brain. Therefore, PPEES may be considered as potential treat-ment in Mn-intoxicated patients.

Transthyretin Exerts Pro-Apoptotic Effects in Human Retinal Microvascular Endothelial Cells Through a GRP78-Dependent Pathway in Diabetic Retinopathy

“…Unresolved ER stress activates proapoptotic and proinflammatory genes, such as those encoding CHOP, which contributes to retinal inflammation and vascular dysfunction in ischemic retinopathy and DR [36]. In endothelial cells, activation of the UPR plays a critical role in regulating cell proliferation, apoptosis and angiogenesis [37], and in this pathway, CHOP is a well-characterized marker for the cell transition from ER stress to apoptosis [38,39]. Recent research has provided the first investigation of a role for ER stress in the dysfunction of angiogenic progenitors in diabetes, and the GRP78-mediated pathway is the key step [40].…”

Effect of trehalose on manganese‐induced mitochondrial dysfunction and neuronal cell damage in mice

“…The decrease of mitochondrial membrane potential (ΔΨm) was evaluated by JC‐1 assay kit (Beyotime) . Briefly, the cells were prepared from striatal tissue and incubated with 0.5 mL JC‐1 dye working liquid at 37℃ for 25 minutes.…”

“…Total intracellular ROS levels were measured using the oxidation‐sensitive fluorescent dye dichlorofluorescein‐diacetate (DCFH‐DA), as described previously . Briefly, single‐cell suspension was prepared from striatal tissue; cells (1 × 10 6 ) were suspended in PBS and incubated with 10 μM DCFH‐DA at 37℃ for 30 minutes.…”

“…The decrease of mitochondrial membrane potential (ΔΨm) was evaluated by JC-1 assay kit (Beyotime). 23 Briefly, the cells were prepared from striatal tissue and incubated with 0.5 mL JC-1 dye working liquid at 37℃ for 25 minutes. Cells were washed and resuspended in 0.5 mL dye buffer, and the results were detected using a flow cytometer (BD FACS Canto II).…”

“…Total intracellular ROS levels were measured using the oxidation-sensitive fluorescent dye dichlorofluoresceindiacetate (DCFH-DA), as described previously. 23 Briefly, single-cell suspension was prepared from striatal tissue; cells (1 × 10 6 ) were suspended in PBS and incubated with 10 μM DCFH-DA at 37℃ for 30 minutes. The increase in fluorescence, which is due to the hydrolysis of DCFH-DA to DCF by non-specific cellular esterase and its subsequent oxidation by peroxides, was measured at 488 nm (excitation) and 525 nm (emission) on a flow cytometer (BD FACS Canto II).…”