Withania somnifera reverses Alzheimer's disease pathology by enhancing low-density lipoprotein receptor-related protein in liver.

A 30-d course of oral administration of a semipurified extract of the root of Withania somnifera consisting predominantly of withanolides and withanosides reversed behavioral deficits, plaque pathology, accumulation of ß-amyloid peptides (Aß) and oligomers in the brains of middle-aged and old APP/PS1 Alzheimer's disease transgenic mice. It was similarly effective in reversing behavioral deficits and plaque load in APPSwInd mice (line J20). The temporal sequence involved an increase in plasma Aß and a decrease in brain Aß monomer after 7 d, indicating increased transport of Aß from the brain to the periphery. Enhanced expression of low-density lipoprotein receptor-related protein (LRP) in brain microvessels and the Aß-degrading protease neprilysin (NEP) occurred 14-21 d after a substantial decrease in brain Aß levels. However, significant increase in liver LRP and NEP occurred much earlier, at 7 d, and were accompanied by a rise in plasma sLRP, a peripheral sink for brain Aß. In WT mice, the extract induced liver, but not brain, LRP and NEP and decreased plasma and brain Aß, indicating that increase in liver LRP and sLRP occurring independent of Aß concentration could result in clearance of Aß. Selective down-regulation of liver LRP, but not NEP, abrogated the therapeutic effects of the extract. The remarkable therapeutic effect of W. somnifera mediated through up-regulation of liver LRP indicates that targeting the periphery offers a unique mechanism for Aß clearance and reverses the behavioral deficits and pathology seen in Alzheimer's disease models.

Redox modification of Akt mediated by the dopaminergic neurotoxin MPTP, in mouse midbrain, leads to down-regulation of pAkt.

Impairment of Akt phosphorylation, a critical survival signal, has been implicated in the degeneration of dopaminergic neurons in Parkinson's disease. However, the mechanism underlying pAkt loss is unclear. In the current study, we demonstrate pAkt loss in ventral midbrain of mice treated with dopaminergic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), when compared to ventral midbrain of control mice treated with vehicle alone. Thiol residues of the critical cysteines in Akt are oxidized to a greater degree in mice treated with MPTP, which is reflected as a 40% loss of reduced Akt. Association of oxidatively modified Akt with the phosphatase PP2A, which can lead to enhanced dephosphorylation of pAkt, was significantly stronger after MPTP treatment. Maintaining the protein thiol homeostasis by thiol antioxidants prevented loss of reduced Akt, decreased association with PP2A, and maintained pAkt levels. Overexpression of glutaredoxin, a protein disulfide oxidoreductase, in human primary neurons helped sustain reduced state of Akt and abolished MPP(+)-mediated pAkt loss. We demonstrate for the first time the selective loss of Akt activity, in vivo, due to oxidative modification of Akt and provide mechanistic insight into oxidative stress-induced down-regulation of cell survival pathway in mouse midbrain following exposure to MPTP.

Cytochrome P4504f, a potential therapeutic target limiting neuroinflammation.

Inflammatory processes are involved in the pathogenesis and/or progression of acute central nervous system (CNS) infection, traumatic brain injury and neurodegenerative disorders among others indicating the need for novel strategies to limit neuroinflammation. Eicosanoids including leukotrienes, particularly leukotriene B(4) (LTB(4)) are principle mediator(s) of inflammatory response, initiating and amplifying the generation of cytokines and chemokines. Cytochrome P450 (Cyp), a family of heme proteins mediate metabolism of xenobiotics and endogenous compounds, such as eicosanoids and leukotrienes. Cytochrome P4504F (Cyp4f) subfamily includes five functional enzymes in mouse. We cloned and expressed the mouse Cyp4f enzymes, assayed their relative expression in brain and examined their ability to hydroxylate the inflammatory cascade prompt LTB(4) to its inactive 20-hydroxylated product. We then examined the role of Cyp4fs in regulating inflammatory response in vitro, in microglial cells and in vivo, in mouse brain using lipopolysacharide (LPS), as a model compound to generate inflammatory response. We demonstrate that mouse brain Cyp4fs are expressed ubiquitously in several cell types in the brain, including neurons and microglia, and modulate inflammatory response triggered by LPS, in vivo and in microglial cells, in vitro through metabolism of LTB(4) to the inactive 20-hydroxy LTB(4). Chemical inhibitor or shRNA to Cyp4fs enhance and inducer of Cyp4fs attenuates inflammatory response. Further, induction of Cyp4f expression lowers LTB(4) levels and affords neuroprotection in microglial cells or mice exposed to LPS. Thus, catalytic activity of Cyp4fs is a novel target for modulating neuroinflammation through hydroxylation of LTB(4).

DJ-1 loss by glutaredoxin but not glutathione depletion triggers Daxx translocation and cell death.

Environmental and genetic causes are implicated in the etiopathogenesis of Parkinson's disease (PD), a neurodegenerative movement disorder. DJ-1, a putative gene recessively linked to early onset PD, functions as an antioxidant, transcriptional co-activator, and molecular chaperone. We examined DJ-1 status following global perturbation of protein thiol homeostasis by depleting cellular antioxidant glutathione or downregulating glutaredoxin 1, a thiol disulfide oxidoreductase, wherein both paradigms generate oxidative stress. While these perturbations did not affect expression of DJ-1 mRNA, downregulation of glutaredoxin 1 but not glutathione depletion caused loss of DJ-1 protein, translocation of Daxx (a death-associated protein) from nucleus, and cell death. Overexpression of wild-type DJ-1, but not the cysteine mutants, prevented Daxx translocation and cytotoxicity. Protease inhibitors prevented constitutive DJ-1 loss. Residual DJ-1 was present in reduced state, indicating that DJ-1 when oxidized was degraded through proteolysis. Thus, loss of DJ-1 occurring through its oxidative modification and subsequent proteolysis mediated through dysregulation of thiol disulfide oxidoreductase may contribute to pathogenesis of sporadic PD, thus providing a link between environmental challenges and constitutive levels of this vital protein.