Neuroprotective and antioxidative effects of pioglitazone in brain tissue adjacent to the ischemic core are mediated by PI3K/Akt and Nrf2/ARE pathways

The present study elucidates the neuroprotective mechanisms of the PPARγ (peroxisome proliferator-activated receptor γ) agonist pioglitazone in survival of ischemic neurons following middle cerebral artery occlusion with reperfusion (MCAO). Intracerebroventricular infusion of pioglitazone over 5 days before and 24 or 48 h after MCAO alleviated neurological impairments, inhibited apoptosis 24 h, and activated the PI3K/Akt pathway along with increased phosphorylation of Akt (ser473) and GSK-3β (ser9) in the peri-infarct cortical areas 48 h after MCAO. In primary cortical neurons, pioglitazone suppressed the glutamate-induced release of lactate dehydrogenase by a PPARγ-dependent mechanism. This protective effect was reversed after co-treatment with PI3K and Akt inhibitors, LY294002 and SH-6, respectively. Pioglitazone enhanced the expression of the antioxidative transcription factor Nrf2 and its target gene protein, heme oxidase-1, in the peri-infarct area. Pioglitazone also increased activation of the antioxidant response element (ARE) in neuronal PC12 cells transfected with the pNQO1-rARE plasmid. We demonstrate in primary cortical neurons from Nrf2 knockout mice that the lack of Nrf2 completely abolished the neuroprotective effects of pioglitazone against oxidative and excitotoxic damage. Our results strongly suggest that the neuroprotective effects of PPARγ in peri-infarct brain tissues comprise the concomitant activation of the PI3K/Akt and Nrf2/ARE pathways. Key messages Pioglitazone inhibits apoptosis in ischemic brain tissue. Pioglitazone acting on PPARγ activates PI3K/Akt pathway in ischemic brain tissue. Pioglitazone activates via Nrf2 the antioxidant defense pathway in injured neurons. Pioglitazone activates the antioxidant response element in neuronal PC12 cells. Pioglitazone fails to protect primary neurons lacking Nrf2 against oxidative damage. Activation of PPARγ supports the survival of viable neurons in peri-infarct regions.

Protective Effects of Total Flavonoids from Lysimachia Christinae on Calcium Oxalate-Induced Oxidative Stress in a Renal Cell Line and Renal Tissue

Background: Flavonoids are compounds with 2-phenylchromone as the basic mother nucleus and are natural antioxidant components of Lysimachia christinae. We previously demonstrated that total flavonoids from L. christinae (TFL) reduce calcium and oxalic acid concentrations in urine and can reduce oxidative stress (OS) in renal tissue, thus, inhibiting calcium oxalate (CaOx) stone formation. The aim of this study was to investigate whether TFL reduced OS in renal tissue, thereby inhibiting CaOx stone formation through the nuclear factor-E2 related factor 2 (Nrf2)/antioxidant response element (ARE) pathway.Methods: The rat model of CaOx stone was established by providing rats with drinking water containing 0.5% glycol and 2% ammonium chloride. After 4 weeks of treatment with different doses of TFL (62.5, 125, and 250 mg/kg/d), body and kidney weights of the rats were measured. CaOx crystal formation was observed under the microscope and the renal tissue contents of superoxide dismutase (SOD) and malondialdehyde (MDA) were analyzed. HK-2 cells were divided into two groups: treatment with CaOx crystals or CaOx crystals + TFL. Other HK-2 cells were treated with small interfering RNA targeting nuclear factor-E2 related factor 2 (Nrf2) and divided into the same two groups. The activities of SOD and content of MDA were measured. The expression of Nrf2, heme oxygenase (HO-1), and NAD(P)H quinone oxidoreductase 1 (NQO-1) were detected using western blot.Results: In the in vitro study, TFL significantly increased nuclear Nrf2 and expression of the downstream antioxidant genes, HO-1 and NQO-1. Furthermore, TFL increased superoxide dismutase activity and decreased the malondialdehyde content, thereby alleviating OS in renal tubular epithelial cells. Moreover, silencing the expression of Nrf2 blocked the protective effect of TFL on CaOx-induced OS. In the in vivo study TFL protected the renal cell line and renal tissue against injury, reduced CaOx-induced OS in renal tissue, and reduced CaOx crystal formation.Conclusions: TFL reduces CaOx-induced OS in renal tissue by activating the nuclear Nrf2/antioxidant response element (ARE) pathway.