Evaluating the effect of ginsenoside Rg1 on CPF-induced brain injury in mice via PI3k/AKT pathway

Organophosphorus pesticides (OPs) have long been used extensively on agricultural land and can lead to significant improvements in crop yields. Due to occupational exposure, humans are exposed to pesticides through dermal contact, inhalation, and ingestion. The effects of OPs on the organism are currently studied for their effects on livers, kidneys, hearts, blood indicators, neurotoxicity, and teratogenic, carcinogenic, and mutagenic effects, while studies in the direction of brain tissue damage have not been reported in detail. Previous reports have confirmed that ginsenoside Rg1 is a prominent and representative tetracyclic triterpenoid derivative rich in ginseng and has good neuroprotective activity. Considering that, the aim of this study was to establish a mouse model of brain tissue injury by using the OP-type pesticide chlorpyrifos (CPF) and to explore the therapeutic effects and possible molecular mechanisms of Rg1. Mice in the experimental group were pre-protected with Rg1 by gavage for 1 week, and brain tissue damage was induced using CPF (5 mg/kg for 1 week) to assess the effect of Rg1 (80 and 160 mg/kg for 3 weeks) in alleviating brain damage. Morris water maze and histopathological analysis were performed to assess cognitive function and pathological changes in the mouse brain, respectively. Protein expression levels of Bax, Bcl-2, Caspase-3, Cl-Cas-3, Caspase-9, Cl-Cas-9, phosphoinositide 3-kinase (PI3K), phosphorylated-PI3K, protein kinase B (AKT), and phosphorylated-AKT were quantified by protein blotting analysis. Rg1 obviously restored CPF-induced oxidative stress damage in mouse brain tissue, increased the levels of antioxidant parameters (total superoxide dismutase, total antioxidative capacity, and glutathione) in the brain, and significantly reduced the overexpression of apoptosis-related proteins induced by CPF. At the same time, Rg1 also markedly attenuated the histopathological changes in the brain induced by CPF exposure. Mechanistically, Rg1 could effectively activate the phosphorylation of PI3K/AKT. Furthermore, molecular docking studies revealed a stronger binding capacity between Rg1 and PI3K. Rg1 attenuated neurobehavioural alterations and reduced lipid peroxidation in the mouse brain to a great extent. Apart from that, Rg1 administration improved brain histopathology in CPF-induced rats. All results suggest that ginsenoside Rg1 has potential antioxidant effects on CPF-induced oxidative brain injury, and it is evident that Rg1 could be used as a promising therapeutic strategy for the study of brain injury from OP poisoning.     

Hepatic uptake and metabolism of phosphatidylcholine associated with high density lipoproteins

Background

Phosphatidylcholine (PC) is the predominant phospholipid associated with high density lipoproteins (HDL). Although the hepatic uptake of cholesteryl esters from HDL is well characterized, much less is known about the fate of PC associated with HDL. Thus, we investigated the uptake and subsequent metabolism of HDL-PC in primary mouse hepatocytes.

Methods and results

The absence of scavenger receptor-BI resulted in a 30% decrease in cellular incorporation of [³H]PC whereas [³H]cholesteryl ether uptake was almost completely abolished. Although endocytosis is not involved in the uptake of cholesteryl esters from HDL, we demonstrate that HDL internalization accounts for 40% of HDL-PC uptake. Extracellular remodeling of HDL by secretory phospholipase A₂ significantly enhances HDL lipid uptake. HDL-PC taken up by hepatocytes is partially converted to triacylglycerols via PC-phospholipase C-mediated hydrolysis of PC and incorporation of diacylglycerol into triacylglcyerol. The formation of triacylglcerol is independent of scavenger receptor-BI and occurs in extralysosomal compartments.

Conclusions and general significance

These findings indicate that HDL-associated PC is incorporated into primary hepatocytes via a pathway that differs significantly from that of HDL-cholesteryl ester, and shows that HDL-PC is more than a framework molecule, as evidenced by its partial conversion to hepatic triacylglycerol.     

Differential participation of phospholipase A(2) isoforms during iron-induced retinal toxicity. Implications for age-related macular degeneration

Both elevated iron concentrations and the resulting oxidative stress condition are common signs in retinas of patients with age-related macular degeneration (AMD). The role of phospholipase A(2) (PLA(2)) during iron-induced retinal toxicity was investigated. To this end, isolated retinas were exposed to increasing Fe(2+) concentrations (25, 200 or 800μM) or to the vehicle, and lipid peroxidation levels, mitochondrial function, and the activities of cytosolic PLA(2) (cPLA(2)) and calcium-independent PLA(2) (iPLA(2)) were studied. Incubation with Fe(2+) led to a time- and concentration-dependent increase in retinal lipid peroxidation levels whereas retinal cell viability was only affected after 60min of oxidative injury. A differential release of arachidonic acid (AA) and palmitic acid (PAL) catalyzed by cPLA(2) and iPLA(2) activities, respectively, was also observed in microsomal and cytosolic fractions obtained from retinas incubated with iron. AA release diminished as the association of cyclooxigenase-2 increased in microsomes from retinas exposed to iron. Retinal lipid peroxidation and cell viability were also analyzed in the presence of cPLA(2) inhibitor, arachidonoyl trifluoromethyl ketone (ATK), and in the presence of iPLA(2) inhibitor, bromoenol lactone (BEL). ATK decreased lipid peroxidation levels and also ERK1/2 activation without affecting cell viability. BEL showed the opposite effect on lipid peroxidation. Our results demonstrate that iPLA(2) and cPLA(2) are differentially regulated and that they selectively participate in retinal signaling in an experimental model resembling AMD.