Saponins of Panax japonicus Confer Neuroprotection against Brain Aging through Mitochondrial Related Oxidative Stress and Autophagy in Rats.

BACKGROUND: Oxidative stress and mitochondrial dysfunction play a vital role in the pathogenesis of brain aging. Saponins from Panax japonicus (SPJ) have attracted much attention for their potential to attenuate age-related oxidative stress as the main ingredient in rhizomes of Panax japonicus. OBJECTIVE: This study aimed to investigate the neuroprotective effects of SPJ on natural aging rats as well as the underlying mechanisms regarding oxidative stress and mitochondrial pathway. METHODS: Sprague-Dawley rats were divided into control groups (3-, 9-, 15- and 24-month old groups) and SPJ-treated groups. For SPJ-treated groups, SPJ were orally administrated to 18-month old rats at doses of 10 mg/kg, 30 mg/kg and 60 mg/kg once daily. Control groups were given the same volume of saline. After the treatment with SPJ or saline for six months, the cortex and hippocampus were rapidly harvested and deposited at -80°C after the rats were decapitated under anesthesia. The neuroprotective effects of SPJ were estimated by histopathological observation, TUNEL detection, biochemical determination and western blotting. RESULTS: SPJ improved pathomorphological changes in neuronal cells and decreased apoptosis in the cortex and hippocampus of aging rats, increased the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), Na+/K+-ATPase, Ca2+-ATPase and Ca2+/Mg2+-ATPase whereas, decreased malondialdehyde (MDA) contents in the cortex of aging rats. Furthermore, the SPJ increased silent mating type information regulation 2 homolog-1 (SIRT1) protein expression, decreased acetylated level of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) in the cortex and hippocampus of aging rats, and reversed the aging-induced decline of Forkhead box O3 (Foxo3a), Superoxide Dismutase 2 (SOD2), microtubule-associated protein light chain 3 (LC3II) and Beclin1 levels in the cortex and hippocampus. CONCLUSION: Our data showed that SPJ conferred neuroprotection partly through the regulation of oxidative stress and mitochondria-related pathways in aging rats.

Saponins from Panax japonicus attenuate age-related neuroinflammation via regulation of the mitogen-activated protein kinase and nuclear factor kappa B signaling pathways.

Neuroinflammation is recognized as an important pathogenic factor for aging and related cognitive disorders. Mitogen-activated protein kinase and nuclear factor kappa B signaling pathways may mediate neuroinflammation. Saponins from Panax japonicus are the most abundant and bioactive members in rhizomes of Panax japonicus, and show anti-inflammatory activity. However, it is not known whether saponin from Panax japonicus has an anti-inflammatory effect in the aging brain, and likewise its underlying mechanisms. Sprague-Dawley rats were divided into control groups (3-, 9-, 15-, and 24-month-old groups) and saponins from Panax japonicus-treated groups. Saponins from Panax japonicus-treated groups were orally administrated saponins from Panax japonicus at three doses of 10, 30, and 60 mg/kg once daily for 6 months until the rats were 24 months old. Immunohistochemical staining and western blot assay results demonstrated that many microglia were activated in 24-month-old rats compared with 3- and 9-month-old rats. Expression of interleukin-1ß, tumor necrosis factor-α, cyclooxygenase-2, and inducible nitric oxide synthase increased. Each dose of saponins from Panax japonicus visibly suppressed microglial activation in the aging rat brain, and inhibited expression levels of the above factors. Each dose of saponins from Panax japonicus markedly diminished levels of nuclear factor kappa B, IκBα, extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38. These results confirm that saponins from Panax japonicus can mitigate neuroinflammation in the aging rat brain by inhibition of the mitogen-activated protein kinase and nuclear factor kappa B signaling pathways.

Chikusetsusaponin V attenuates lipopolysaccharide-induced liver injury in mice.

Chikusetsusaponin V (CsV), a saponin from Panax japonicus, has been reported to inhibit inflammatory responses in lipopolysaccharide (LPS)-induced macrophage cells. However, whether CsV could alleviate LPS-induced liver injury in vivo and the potential mechanisms involved remain unclear. In the present study, we investigated the anti-inflammatory effects of CsV on LPS-induced acute liver injury in mice and further explored the potential mechanisms involved. Our results showed that CsV significantly attenuated elevation of alanine transaminase (ALT) and aspartate aminotransferase (AST) levels and improved liver histopathological changes in LPS-induced mice. In addition, CsV decreased serum tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß) levels and inhibited mRNA expressions of inducible nitric oxide synthase (iNOS), TNF-α and IL-1ß in LPS challenged mice. Furthermore, CsV inhibited nuclear factor kappa B (NF-κB) activation by downregulating phosphorylated NF-κB, IκB-α, ERK, c-Jun N-terminal kinase (JNK) and p38 levels in the liver tissue, which ultimately decreased nucleus NF-κB protein level. In conclusion, our data suggested that CsV could be a promising drug for preventing LPS challenged liver injury since it attenuated LPS-induced inflammatory responses, partly via inhibiting NF-κB and MAPK signaling pathways.

[Effects of the Saponins from Panax japonicus on Intestinal Epithelial Tight Junction Proteins in Aging Rats].

Objective: To investigate the moderating effects of total saponins of Panax japonicus on intestinal epithelial tight junction proteins in aging rats,and to explore the potential mechanism. Methods: SD rats were divided into adult group( 6 months),old model group( 24 months),and different doses( 10,30 and 60 mg / kg) of total saponins of Panax japonicus treatment groups. Levels of tight junction proteins( Occludin and ZO-1),anti-oxidative pathway proteins( Nrf2、HO-1 and NQO-1),mitochondrial biogenesis related proteins( Sirt1 and PGC-1α) and p-AMPK in the ileum were determined by immunohistochemistry staining. Results: Compared with adult group,the expressions of Occludin,ZO-1,Nrf2,HO-1,NQO-1,Sirt1 and PGC-1α of aging rats were obviously decreased( P < 0. 01),and p-AMPK was inhibited in the ileum of aging rats. Compared with aging model rats,total saponins of Panax japonicus increased the expressions of Occludin,ZO-1,Nrf2,HO-1,NQO-1,Sirt1 and PGC-1α( P < 0. 05 or P < 0. 01),and activated p-AMPK in the ileum of aging rats. Conclusion: The decreased level of intestinal tight junction proteins in the ileum of aging rats may be related to oxidative stress. Total saponins of Panax japonicus can up-regulate the level of intestinal tight junction proteins to improve the intestinal mucosal barrier dysfunction in the ileum of aging rat via reducing the levels of oxidative stress.

Chikusetsu saponin V attenuates MPP+-induced neurotoxicity in SH-SY5Y cells via regulation of Sirt1/Mn-SOD and GRP78/caspase-12 pathways.

Studies have shown that saponins from Panax japonicus (SPJ) possess neuroprotective effects. However, whether Chikusetsu saponin V (CsV), the most abundant member of SPJ, can exert neuroprotective effects against 1-methyl-4-phenylpyridinium ion (MPP+)-induced cytotoxicity is not known. In this study, we aimed to investigate the neuroprotective effects of CsV on MPP+-induced cytotoxicity in human neuroblastoma SH-SY5Y cells and explore its possible mechanisms. Our results show that CsV attenuates MPP+-induced cytotoxicity, inhibits ROS accumulation, and increases mitochondrial membrane potential dose-dependently. We also found that levels of Sirt1 protein and Mn-SOD mRNA significantly decreased in MPP+-treated group but were restored with CsV treatment in a dose-dependent manner. Furthermore, GRP78 protein and Caspase-12 mRNA levels were elevated by MPP+ exposure but reversed by CsV treatment. CsV inhibited the MPP+-induced downregulation of Bcl-2 and up-regulation of Bax in a dose-dependent manner and, thus, increased the ratio of Bcl-2/Bax. Overall, these results suggest that Sirt1/Mn-SOD and GRP78/Caspase-12 pathways might be involved in the CsV-mediated neuroprotective effects.

[Protective Effect of Total Flavonoids of Epimedium on D-galactose-induced Senescence in H9c2 Cells].

OBJECTIVE: To investigate the protective effect of Total Flavonids of Epimedium (TFE) on D-galactose-induced H9c2 cells senescence and to explore the underlying mechanisms. METHODS: D-galactosed (50 mmol/L) were used to induce the aging of H9c2 cells. Different concentrations of TFE (5,25 and 50 µg/mL) were added into the medium before the use of D-galactosed. Cells senescence was identified by ß-galactosidase and the changes in cell morphology were observed. The activity of superoxide dismutase(SOD) and the content of malondial dehyde (MDA) were measured. Reactive oxygen species( ROS) was observed by DCFH-DA detection and the apoptosis was tested by Hochest. RESULTS: In the D-gal group,the number of ß-galactosidase-positive cells, the content of MDA and the fluorescence intensity of ROS were markedly increased. In the meanwhile,the chromatin was condensated and the apoptotic bodies were seen by using Hochest. Compared with the D-gal group, TFE apparently decreased the quantity of ß-galactosidase-positive cells, the content of MDA, and the florescence intensity of ROS, increased the activity of SOD, and enhanced the condition of chromatin. CONCLUSION: TFE can confront D-galactose-induced senescence in H9c2 cells by increasing the ability of antioxidant and reducing the number of apoptosis.

Activation of epidermal growth factor receptor mediates reperfusion arrhythmias in anaesthetized rats.

AIMS: Epidermal growth factor receptor (EGFR) plays a critical role in the development and function of the heart. Previous studies have demonstrated that EGFR is involved in regulating electrical excitability of the heart. The present study was designed to investigate whether EGFR activation would mediate cardiac arrhythmias induced by reperfusion in anaesthetized rats. METHODS AND RESULTS: Reperfusion arrhythmias were induced by 10 min ligation of the left anterior descending coronary artery, followed by a 30 min reperfusion in anaesthetized rats. The incidence and severity of cardiac arrhythmias were significantly reduced by pre-treatment with the EGFR kinase inhibitor AG556. The phosphorylation level of myocardial EGFR was increased during ischaemia and at early reperfusion. Intramyocardial transfection of EGFR siRNA reduced EGFR mRNA and protein, and decreased the incidence of ventricular fibrillation induced by reperfusion. Interestingly, tyrosine phosphorylation levels of cardiac Na(+) channels (I(Na)) and L-type Ca(2+) channels (I(Ca,L)) were significantly increased at time points corresponding to the alteration of EGFR phosphorylation levels during reperfusion. AG556 pre-treatment countered the increased tyrosine phosphorylation level of Na(+) and L-type Ca(2+) channels induced by reperfusion. Patch-clamp studies proved that AG556 could inhibit I(Na) and I(Ca,L) in rat ventricular myocytes. No significant alteration was observed in tyrosine phosphorylation levels of cardiac Kv4.2 and Kir2.1 channels during reperfusion. CONCLUSION: These results demonstrate for the first time that EGFR plays an important role in the genesis of arrhythmias induced by reperfusion, which is likely mediated at least in part by enhancing tyrosine phosphorylation of cardiac Na(+) and L-type Ca(2+) channels.