Incidence and severity of experimental allergic encephalomyelitis and cerebral prostaglandin synthesis in essential fatty acid deficient and aspirin-treated rats

Aspirin and multiple sclerosis

Aspirin is widely used to lessen the risks of cardiovascular events. Some studies suggest that patients with multiple sclerosis have an increased risk for some cardiovascular events, for example, venous thromboembolism and perhaps ischemic strokes, raising the possibility that aspirin could lessen these increased risks in this population or subgroups (patients with limited mobility and/or antiphospholipid antibodies). However, aspirin causes a small increased risk of hemorrhagic stroke, which is a concern as it could potentially worsen a compromised blood-brain barrier. Aspirin has the potential to ameliorate the disease process in multiple sclerosis (for example, by limiting some components of inflammation), but aspirin also has the potential to inhibit mitochondrial complex I activity, which is already reduced in multiple sclerosis. In an experimental setting of a cerebral ischemic lesion, aspirin promoted the proliferation and/or differentiation of oligodendrocyte precursors, raising the possibility that aspirin could facilitate remyelination efforts in multiple sclerosis. Other actions by aspirin may lead to small improvements of some symptoms (for example, lessening fatigue). Here we consider potential benefits and risks of aspirin usage by patients with multiple sclerosis.

Nuclear factor kappa B (NF-κB) in multiple sclerosis pathology

The nuclear factor kappa B (NF-κB) signaling cascade plays a critical role in the regulation of immune and inflammatory responses and has been implicated in the pathogenesis of autoimmune demyelinating diseases such as multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), the main animal model of MS. NF-κB is essential for peripheral immune cell activation and the induction of pathology, but also plays crucial roles in resident cells of the central nervous system (CNS) during disease development. Here we review recent evidence clarifying the role of NF-κB in the different cell compartments contributing to MS pathology and its implications for the development of therapeutic strategies for the treatment of MS and other demyelinating pathologies of the CNS.

Role of prostaglandins in neuroinflammatory and neurodegenerative diseases

Increasing data demonstrates that inflammation participates in the pathophysiology of neurodegenerative diseases. Among the different inflammatory mediators involved, prostaglandins play an important role. The effects induced by prostaglandins might be mediated by activation of their known receptors or by nonclassical mechanisms. In the present paper, we discuss the evidences that link prostaglandins, as well as the enzymes that produce them, to some neurological diseases.

Sodium salicylate-induced amelioration of experimental autoimmune encephalomyelitis in Lewis rats is associated with the suppression of inducible nitric oxide synthase and cyclooxygenases

We studied the effects of oral administration of sodium salicylate on the expression of the pro-inflammatory mediators, nitric oxide synthase (iNOS) and cyclooxygenase- (COX-) 1 and 2, in rats with experimental autoimmune encephalomyelitis (EAE). Sodium salicylate (200 mg/kg) was administered orally for 13 days after the induction of EAE by immunization with guinea pig myelin basic protein and complete Freund's adjuvant. The onset (P<0.0001) and severity (P<0.05) of EAE paralysis in salicylate-treated animals were delayed and suppressed significantly compared with vehicle-treated controls. Western blot analysis showed that expression of COX-2 and iNOS, but not COX-1, decreased significantly in the spinal cords of salicylate-treated rats compared with vehicle-treated controls (P<0.05) and this finding was paralleled by immunohistochemical observations. These results suggest that the amelioration by salicylate of paralysis in rats with EAE is mediated in part by the suppression of COX and iNOS.

Prostaglandins and inhibitors of arachidonate metabolism suppress experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is an autoimmune inflammatory disease of the central nervous system (CNS). It is an animal model of post-infectious encephalomyelitis and multiple sclerosis (MS). Acute EAE is mediated by macrophages and by T helper 1 (Th1) lymphocytes directed against brain antigens. Inflammation in EAE could potentially be modified by prostaglandins (PG) secreted by blood monocytes (Mo) and brain glial cells. PGE elevates cAMP, which inhibits Mo function and selectively blocks secretion of cytokines by Th1 cells. In the present study, we found that a long-acting PGE1 analogue (LAPGE) inhibited clinical and histological EAE. Indomethacin (INDO) also suppressed active EAE. The combination of INDO plus LAPGE inhibited disease further, possibly by allowing LAPGE to function unopposed by immunostimulatory PG. EAE was suppressed when these agents were administered from the time of immunization or from the onset of clinical disease. The combination of INDO plus LAPGE also inhibited delayed-type hypersensitivity (DTH) reactions to myelin basic protein (MBP), and diminished in vitro lymphocyte responses to mitogens and MBP. PGE analogues and modifiers of arachidonate metabolism block autoimmune responses to brain antigens in vitro and in vivo, and may ameliorate inflammatory and autoimmune diseases of the brain and other organs.

Dietary fat and neoplasia--the role of net energy in enhancement of carcinogenesis: effects of fat and calories on the immune system

The mechanism by which carcinogenesis is enhanced by dietary fat is not understood. We know that a minimum level of essential fatty acids (EFA) is necessary for mammary tumor development and that this level probably exceeds the normal requirements of rats. Once the minimum level of EFA has been supplied, the calorie contribution of dietary fat may account for its enhancement of carcinogenesis. In this regard, we must recognize that the efficiency with which dietary energy is utilized is known to increase as the fat content of the diet is raised. Hence even when fed isocalorically to low fat diets, high fat diets will provide more net energy. Modulation of host immunity has been proposed as a mechanism of action of both fat and calorie intake on neoplasia. We review the literature examining the effects of fat and calories on the cell-mediated immune system, that arm of the immune system most directly responsible for the killing of neoplastic cells.

Alterations in cerebral and microvascular prostaglandin synthesis by manipulation of dietary essential fatty acids

Sprague-Dawley rats were fed one of three purified diets--10% corn oil, 10% hydrogenated coconut oil, or 10% linseed oil--through two generations. At 60-80 days of age the animals were sacrificed. The fatty acyl composition of phosphatidylcholine, phosphatidylethanolamine, plasmalogen phosphatidylethanolamine, and combined phosphatidylinositol/phosphatidylserine from cerebral cortex and isolated cerebral microvessels was determined. Brain slice prostaglandin F2 alpha or microvascular prostacyclin synthesis was also measured. Major changes were noted in the fatty acid profiles, most dramatically in the phosphatidylethanolamine and ethanolamine plasmalogen fractions, with an active rise in docosahexaenoic acid resulting from linseed oil feeding. A depression in prostaglandin F2 alpha synthesis was seen in brain slices of hydrogenated coconut oil- and linseed oil-fed rats. Such a depression was also observed in microvascular prostaglandin synthesis at basal and stimulated levels but not in control incubations. The potential importance of these findings to cerebral microcirculation and hemostasis is discussed.