Association Between Multiple Sclerosis Risk and Human Immunodeficiency Virus Infection: Insights and Challenges

Multiple sclerosis (MS) is a convoluted autoimmune and inflammatory disease of the central nervous system (CNS) in which the protective myelin sheath is eroded and the underlying nerve fibers are damaged. There is no conclusive knowledge on the role played by different etiological factors in its development, and studies have shown that it primarily results due to complex interactions between the genetic, geographic and infectious components. Among the risk factors reported to have a possible role in MS development, retroviruses also appear to influence it. Studies suggest human immunodeficiency virus (HIV) infection to be inversely related to MS risk, but to date, the association between the two remains enigmatic. This protective inverse association has become an area of active research and the most plausible explanations for this may be immune suppression and/or antiretroviral medications. The purpose of writing this chapter is to provide background information on the unfathomable relationship between HIV infection and the risk of developing MS while at the same time providing description of the insights garnered from recent studies. While highlighting the application of ART (antiretroviral therapy) as budding future alternative for MS management, this chapter provides momentum for further studies

Reduction of lipoxidative load by secretory phospholipase A2 inhibition protects against neurovascular injury following experimental stroke in rat

<p>Abstract</p> <p>Background</p> <p>In animal models, ischemia reperfusion (IR) injury triggers membrane lipid degradation and accumulation of lipoxidative exacerbations in neurovascular unit, leading to blood brain barrier (BBB) damage and neurologic deficits. In this study, we investigated whether impeding membrane lipid breakdown by inhibiting secretory phospholipase A2 (sPLA2) activity reduces BBB leakage, leading to neuroprotection and functional recovery.</p> <p>Methods</p> <p>Focal cerebral IR injury was induced by middle cerebral artery occlusion (MCAO) in adult male rats. A sPLA2 inhibitor, 7,7-dimethyleicosadienoic acid (DEDA), was administered following IR injury. DEDA-treated animals were compared with vehicle-treated in terms of BBB leakage, edema, infarct volume, and neurological deficit. Membrane lipid degradation and the expression/activity of sPLA2 were also assessed. The role of one of the sPLA2 products, arachidonic acid (AA), on the morphology of the differentiated neuronal cell PC12 was examined by light microscopy.</p> <p>Results</p> <p>Treatment with DEDA after IR injury not only reduced BBB leakage but also decreased infarct volume and improved neurologic function. The treatment attenuated both the activity of sPLA2 and the levels of sPLA2-derived oxidized products. The metabolites of lipid oxidation/peroxidation, including the protein carbonyl, were reduced as well. The treatment also restored the levels of glutathione, indicating attenuation of oxidative stress. I<it>n vitro </it>treatment of PC12 cells with DEDA did not restore the AA-mediated inhibition of neurite formation and the levels of glutathione, indicating that effect of DEDA is up stream to AA release.</p> <p>Conclusion</p> <p>sPLA2-derived oxidative products contribute to significant neurovascular damage, and treatment with sPLA2 inhibitor DEDA ameliorates secondary injury by reducing exacerbations from lipoxidative stress.</p

Histone Deacetylase Inhibitor Upregulates Peroxisomal Fatty Acid Oxidation And Inhibits Apoptotic Cell Death In Abcd1-deficient Glial Cells

In X-ALD, mutation/deletion of ALD gene (ABCD1) and the resultant very long chain fatty acid (VLCFA) derangement has dramatically opposing effects in astrocytes and oligodendrocytes. While loss of Abcd1 in astrocytes produces a robust inflammatory response, the oligodendrocytes undergo cell death leading to demyelination in X-linked adrenoleukodystrophy (X-ALD). The mechanisms of these distinct pathways in the two cell types are not well understood. Here, we investigated the effects of Abcd1-knockdown and the subsequent alteration in VLCFA metabolism in human U87 astrocytes and rat B12 oligodendrocytes. Loss of Abcd1 inhibited peroxisomal beta-oxidation activity and increased expression of VLCFA synthesizing enzymes, elongase of very long chain fatty acids (ELOVLs) (1 and 3) in both cell types. However, higher induction of ELOVL's in Abcd1-deficient B12 oligodendrocytes than astrocytes suggests that ELOVL pathway may play a prominent role in oligodendrocytes in X-ALD. While astrocytes are able to maintain the cellular homeostasis of antiapoptotic proteins, Abcd1-deletion in B12 oligodendrocytes downregulated the anti-apototic (Bcl-2 and Bcl-xL) and cell survival (phospho-Erk1/2) proteins, and upregulated the pro-apoptotic proteins (Bad, Bim, Bax and Bid) leading to cell loss. These observations provide insights into different cellular signaling mechanisms in response to Abcd1-deletion in two different cell types of CNS. The apoptotic responses were accompanied by activation of caspase-3 and caspase-9 suggesting the involvement of mitochondrial-caspase-9-dependent mechanism in Abcd1-deficient oligodendrocytes. Treatment with histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) corrected the VLCFA derangement both in vitro and in vivo, and inhibited the oligodendrocytes loss. These observations provide a proof-of principle that HDAC inhibitor SAHA may have a therapeutic potential for X-ALD

A Novel Role of Lactosylceramide in the Regulation of Lipopolysaccharide/Interferon-γ-Mediated Inducible Nitric Oxide Synthase Gene Expression: Implications for Neuroinflammatory Diseases

In the present study a possible role of glycosphingolipids (GSLs) in inducible nitric oxide synthase (iNOS) gene expression and nitric oxide (NO) production after spinal cord injury (SCI) in rats has been established. In primary rat astrocytes lipopolysaccharide (LPS) and interferon-γ (IFN-γ) treatment increased the intracellular levels of lactosylceramide (LacCer) and induced iNOS gene expression. D-Threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol·HCI (PDMP), a glucosylceramide synthase and LacCer synthase (galactosyltransferase, GalT-2) inhibitor, inhibited LPS/IFN-γ induced iNOS expression, which was reversed by exogenously supplied LacCer, but not by other glycosphingolipids. LPS/IFN-γ caused a rapid increase in the activity of GalT-2 and synthesis of LacCer. Silencing of GalT-2 gene with the use of antisense oligonucleotides resulted in decreased LPS/IFN-γ-induced iNOS, TNF-α, and IL-1β gene expression. The PDMP-mediated reduction in LacCer production and inhibition of iNOS expression correlated with decreased Ras and ERK1/2 activation along with decreased IκB phosphorylation, NF-κB DNA binding activity, and NF-κB-luciferase reporter activity. LacCer-mediated Ras activation was redox-mediated and was attenuated by antioxidants N-acetyl cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC). In vivo administration of PDMP after SCI resulted in improved functional outcome (Basso, Beattie, Bresnahan score); inhibition of iNOS, TNF-α, and IL-1β expression; decreased neuronal apoptosis; and decreased tissue necrosis and demyelination. The in vivo studies supported the conclusions drawn from cell culture studies and provided evidence for the possible role of GalT-2 and LacCer in SCI-induced inflammation and pathology. To our knowledge this is the first report of a role of LacCer in iNOS expression and the advantage of GSL depletion in attenuating post-SCI inflammation to improve the outcome of SCI

Inhibition of NF-κB activation by 5-lipoxygenase inhibitors protects brain against injury in a rat model of focal cerebral ischemia

BACKGROUND: Stroke is one of the leading causes of death worldwide and a major cause of morbidity and mortality in the United States of America. Brain ischemia-reperfusion (IR) triggers a complex series of biochemical events including inflammation. Leukotrienes derived from 5-lipoxygenase (5-LOX) cause inflammation and are thus involved in the pathobiology of stroke injury. METHODS: To test the neuroprotective efficacy of 5-LOX inhibition in a rat model of focal cerebral IR, ischemic animals were either pre- or post-treated with a potent selective 5-LOX inhibitor, (N- [3-[3-(-fluorophenoxy) phenyl]-1-methyl-2-propenyl]-N-hydroxyurea (BW-B 70C). They were evaluated at 24 h after reperfusion for brain infarction, neurological deficit score, and the expression of 5-LOX. Furthermore, the mechanism and the anti-inflammatory potential of BW-B 70C in the regulation of nuclear factor kappa B (NF-κB) and inflammatory inducible nitric oxide synthase (iNOS) were investigated both in vivo and in vitro. RESULTS AND DISCUSSION: Both pre- and post-treatment with BW-B 70C reduced infarctions and improved neurological deficit scores. Immunohistochemical study of brain sections showed IR-mediated increased expression of 5-LOX in the neurons and microglia. BW-B 70C down-regulated 5-LOX and inhibited iNOS expression by preventing NF-κB activation. Two other structurally different 5-LOX inhibitors were also administered post IR: caffeic acid and 2, 3, 5-trimethyl-6- [12-hydroxy-5, 10-dodecadiynyl]-1, 4-benzoquinone (AA-861). As with BW-B 70C, they provided remarkable neuroprotection. Furthermore, in vitro, BW-B 70C inhibited lipopolysaccharide (LPS) mediated nitric oxide production, iNOS induction and NF-κB activation in the BV2 microglial cell line. Treating rat primary microglia with BW-B70C confirmed blockage of LPS-mediated translocation of the p65 subunit of NF-κB from cytosol to nucleus. CONCLUSION: The study demonstrates the neuroprotective potential of 5-LOX inhibition through down-regulation of NF-κB in a rat model of experimental stroke

Administration of S-nitrosoglutathione after traumatic brain injury protects the neurovascular unit and reduces secondary injury in a rat model of controlled cortical impact

<p>Abstract</p> <p>Background</p> <p>Traumatic brain injury (TBI) is a major cause of preventable death and serious morbidity in young adults. This complex pathological condition is characterized by significant blood brain barrier (BBB) leakage that stems from cerebral ischemia, inflammation, and redox imbalances in the traumatic penumbra of the injured brain. Once trauma has occurred, combating these exacerbations is the keystone of an effective TBI therapy. Following other brain injuries, nitric oxide modulators such as S-nitrosoglutathione (GSNO) maintain not only redox balance but also inhibit the mechanisms of secondary injury. Therefore, we tested whether GSNO shows efficacy in a rat model of experimental TBI.</p> <p>Methods</p> <p>TBI was induced by controlled cortical impact (CCI) in adult male rats. GSNO (50 μg/kg body weight) was administered at two hours after CCI. GSNO-treated injured animals (CCI+GSNO group) were compared with vehicle-treated injured animals (CCI+VEH group) in terms of tissue morphology, BBB leakage, edema, inflammation, cell death, and neurological deficit.</p> <p>Results</p> <p>Treatment of the TBI animals with GSNO reduced BBB disruption as evidenced by decreased Evan's blue extravasation across brain, infiltration/activation of macrophages (ED1 positive cells), and reduced expression of ICAM-1 and MMP-9. The GSNO treatment also restored CCI-mediated reduced expression of BBB integrity proteins ZO-1 and occludin. GSNO-mediated improvements in tissue histology shown by reduction of lesion size and decreased loss of both myelin (measured by LFB staining) and neurons (assayed by TUNEL) further support the efficacy of GSNO therapy. GSNO-mediated reduced expression of iNOS in macrophages as well as decreased neuronal cell death may be responsible for the histological improvement and reduced exacerbations. In addition to these biochemical and histological improvements, GSNO-treated injured animals recovered neurobehavioral functions as evaluated by the rotarod task and neurological score measurements.</p> <p>Conclusion</p> <p>GSNO is a promising candidate to be evaluated in humans after brain trauma because it not only protects the traumatic penumbra from secondary injury and improves overall tissue structure but also maintains the integrity of BBB and reduces neurologic deficits following CCI in a rat model of experimental TBI.</p

AICAR inhibits adipocyte differentiation in 3T3L1 and restores metabolic alterations in diet-induced obesity mice model

BACKGROUND: Obesity is one of the principal causative factors involved in the development of metabolic syndrome. AMP-activated protein kinase (AMPK) is an energy sensor that regulates cellular metabolism. The role of AMP-activated protein kinase in adipocyte differentiation is not completely understood, therefore, we examined the effect of 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), a pharmacological activator of AMP-activated protein kinase (AMPK) on adipocyte differentiation in 3T3L1 cells and in a mouse Diet induced obesity (DIO) model. METHODS: To examine the effect of AICAR on adipocyte differentiation in 3T3L1 cells and in a mouse Diet induced obesity (DIO) model, 3T3L1 cells were differentiatied in the presence or absence of different concentration of AICAR and neutral lipid content and expression of various adipocyte-specific transcription factors were examined. In vivo study, treated and untreated mice with AICAR (0.1–0.5 mg/g body weight) were fed high-fat diet (60% kcal% fat) to induce DIO and several parameters were studied. RESULTS: AICAR blocked adipogenic conversion in 3T3L1 cells along with significant decrease in the neutral lipid content by downregulating several adipocyte-specific transcription factors including peroxisome proliferators-activated receptor γ (PPARγ), C/EBPα and ADD1/SREBP1, which are critical for adipogenesis in vitro. Moreover, intraperitoneal administration of AICAR (0.5 mg g/body weight) to mice fed with high-fat diet (60% kcal% fat) to induce DIO, significantly blocked the body weight gain and total content of epididymal fat in these mice over a period of 6 weeks. AICAR treatment also restored normal adipokine levels and resulted in significant improvement in glucose tolerance and insulin sensitivity. The reduction in adipose tissue content in AICAR treated DIO mice was due to reduction in lipid accumulation in the pre-existing adipocytes. However, no change was observed in the expression of PPARγ, C/EBPα and ADD1/SREBP1 transcription factors in vivo though PGC1α expression was significantly induced. CONCLUSION: This study suggests that AICAR inhibits adipocyte differentiation via downregulation of expression of adipogenic factors in vitro and reduces adipose tissue content in DIO mice by activating expression of PGC1α without inhibiting adipocyte-specific transcription factors in DIO mice

S-Nitrosoglutathione reduces oxidative injury and promotes mechanisms of neurorepair following traumatic brain injury in rats

<p>Abstract</p> <p>Background</p> <p>Traumatic brain injury (TBI) induces primary and secondary damage in both the endothelium and the brain parenchyma, collectively termed the neurovascular unit. While neurons die quickly by necrosis, a vicious cycle of secondary injury in endothelial cells exacerbates the initial injury in the neurovascular unit following TBI. In activated endothelial cells, excessive superoxide reacts with nitric oxide (NO) to form peroxynitrite. Peroxynitrite has been implicated in blood brain barrier (BBB) leakage, altered metabolic function, and neurobehavioral impairment. S-nitrosoglutathione (GSNO), a nitrosylation-based signaling molecule, was reported not only to reduce brain levels of peroxynitrite and oxidative metabolites but also to improve neurological function in TBI, stroke, and spinal cord injury. Therefore, we investigated whether GSNO promotes the neurorepair process by reducing the levels of peroxynitrite and the degree of oxidative injury.</p> <p>Methods</p> <p>TBI was induced by controlled cortical impact (CCI) in adult male rats. GSNO or 3-Morpholino-sydnonimine (SIN-1) (50 μg/kg body weight) was administered orally two hours following CCI. The same dose was repeated daily until endpoints. GSNO-treated (GSNO group) or SIN-1-treated (SIN-1 group) injured animals were compared with vehicle-treated injured animals (TBI group) and vehicle-treated sham-operated animals (Sham group) in terms of peroxynitrite, NO, glutathione (GSH), lipid peroxidation, blood brain barrier (BBB) leakage, edema, inflammation, tissue structure, axon/myelin integrity, and neurotrophic factors.</p> <p>Results</p> <p>SIN-1 treatment of TBI increased whereas GSNO treatment decreased peroxynitrite, lipid peroxides/aldehydes, BBB leakage, inflammation and edema in a short-term treatment (4-48 hours). GSNO also reduced brain infarctions and enhanced the levels of NO and GSH. In a long-term treatment (14 days), GSNO protected axonal integrity, maintained myelin levels, promoted synaptic plasticity, and enhanced the expression of neurotrophic factors.</p> <p>Conclusion</p> <p>Our findings indicate the participation of peroxynitrite in the pathobiology of TBI. GSNO treatment of TBI not only reduces peroxynitrite but also protects the integrity of the neurovascular unit, indicating that GSNO blunts the deleterious effects of peroxynitrite. A long-term treatment of TBI with the same low dose of GSNO promotes synaptic plasticity and enhances the expression of neurotrophic factors. These results support that GSNO reduces the levels of oxidative metabolites, protects the neurovascular unit, and promotes neurorepair mechanisms in TBI.</p