Effect of Methanol Intoxication on Rat Neutrophil Functions

Mechanistic Insights into Aspartame-induced Immune Dysregulation

Background & Objective:

Aspartame, (L-aspartyl-L-phenylalanine methyl ester) is a widely used artificial sweetener but studies raise safety concerns regarding the use of aspartame metabolites especially methanol. In this review, we aimed to provide mechanistic insights that may explain aspartame-induced immune dysregulation.

Findings:

While evidence is limited, from the available literature, possible mechanisms for immune dysfunction associated with aspartame include (1) alterations in bidirectional communication between neuro-immune-endocrine responses (2) disruption of the brain-gut-microbiota-immune axis (3) induction of oxidative stress in immune cells and organs and lastly (4) the immune-activation effect of methanol.

Conclusion:

Further studies are needed to confirm above proposed mechanisms that may explain aspartame- induce immune dysregulation.

Toxicity of methanol and formaldehyde towards Saccharomyces cerevisiae as assessed by DNA microarray analysis

To assess the toxicity of the C1 compounds methanol and formaldehyde, gene expression profiles of treated baker's yeast were analyzed using DNA microarrays. Among approximately 6,000 open reading frames (ORFs), 314 were repressed and 375 were induced in response to methanol. The gene process category "energy" comprised the greatest number of induced genes while "protein synthesis" comprised the greatest number of repressed genes. Products of genes induced by methanol were mainly integral membrane proteins or were localized to the plasma membrane. A total of 622 and 610 ORFs were induced or repressed by formaldehyde, respectively. More than one-third of the genes found to be strongly repressed by formaldehyde belonged to the "protein synthesis" functional category. Conversely, genes in the subcategory of "nitrogen, sulfur, and selenium metabolism" within "metabolism" and in the category of "cell rescue, defense, and virulence" were up-regulated by exposure to formaldehyde. Our data suggest that membrane structure is a major target of methanol toxicity, while proteins were major targets of formaldehyde toxicity.

Inhibition of function of T cell subpopulations and decrease in cytokine production during subacute poisoning with various toxicants

Experiments on outbred albino rats showed that subacute intoxication with organophosphorus compounds dimethyldichlorovinyl phosphate and malathion primarily decreased functional activity of Th1 lymphocytes, immune reactions associated with these cells, and interferon-g production compared to that of Th2 lymphocytes and interleukin-4 synthesis. Acrylic acid nitrile and methanol produced the opposite effect. Sulfur mustard and sodium arsenite were equally potent in reducing the function of Th1 and Th2 lymphocytes and production of cytokines.

Effect of methanol intoxication on spcific immune functions of albino rats

Our previous studies revealed that methanol intoxication significantly altered the non-specific immune functions in albino rats. The present investigation focuses on the effect of methanol on certain specific immune functions of cell mediated immunity such as footpad thickness, leukocyte migration inhibition test (LMI) and antibody levels. In addition, serum interleukins (IL-2, IL-4, TNF-alpha and IFN-gamma), and splenic lymphocyte subsets were measured after an immune challenge. The specific immune function tests were carried out in three different groups of albino rats, which include control, 15 and 30 days methanol intoxication. Our study reports that animal body weight, organ weight ratio, lymphoid cell counts, footpad thickness, antibody titer, IL-2, TNF-alpha, IFN-gamma, Pan T cell, CD4, macrophages, MHC class II molecule expression, and B cell counts were significantly decreased compared to control animals nevertheless, LMI, IL-4, and DNA single strand breakage were increased significantly. Plasma corticosterone level was significantly increased in the 15 days group whereas the 30 days methanol intoxication group showed considerable decrease in corticosterone level compared with control animals. Therefore, our investigation concluded that repeated exposure of methanol profoundly suppressed the cell mediated and humoral immune functions in albino rats.

Methanol‐Induced Oxidative Stress in Rat Lymphoid Organs

Methanol is primarily metabolized by oxidation to formaldehyde and then to formate. These processes are accompanied by formation of superoxide anion and hydrogen peroxide. This paper reports data on the effect of methanol on antioxidant status and lipid peroxidation in lymphoid organs such as the spleen, thymus, lymph nodes and bone marrow of rats. Male Wistar albino rats were intoxicated with methanol (2.37 g/kg b.w intraperitoneally) for detecting toxicity levels for one day, 15 d and 30 d, respectively. Administration of methanol at 15 and 30 d significantly (p<0.05) increased lipid peroxidation and decreased the enzymatic (superoxide dismutase, catalase, glutathione peroxidase) and non-enzymatic antioxidants (reduced glutathione and vitamin C) in lymphoid organs. However, lipid peroxidation and enzymatic and non-enzymatic antioxidants in the acute methanol exposed group animals were found to be significantly (p<0.05) increased. In one day methanol intoxication, the levels of free radicals initially increased, and to remove these free radicals, antioxidants levels were elevated, which generally prevented oxidative cell damage. But in longer periods of intoxication, when the generation of reactive free radicals overwhelmed the antioxidant defense, lipid peroxidation increased. Further, decreased antioxidants in 15 and 30 d methanol intoxication may have been due to overutilization of non-enzymatic and enzymatic antioxidants to scavenge the products of lipid peroxidation. In addition, the liver and kidney markers of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea and creatinine significantly increased. This study concludes that exposure to methanol causes oxidative stress by altering the oxidant/antioxidant balance in lymphoid organs of the rat.