Effect of exposure to low doses of ozone on interleukin 17A expression during progressive neurodegeneration in the rat hippocampus.

INTRODUCTION: Chronic exposure to low doses of ozone causes oxidative stress and loss of regulation of the inflammatory response, leading to progressive neurodegeneration. OBJECTIVE: We studied the effect of chronic exposure to low doses of ozone on IL-17A concentration and expression in neurons, microglia, astrocytes, and T cells in the rat hippocampus. METHODS: We used 72 Wistar rats, divided into 6 groups (n=12): a control group (no ozone exposure) and 5 groups exposed to ozone (0.25ppm, 4h daily) for 7, 15, 30, 60, and 90 days. We processed 6 rats from each group to quantify IL-17A by ELISA; the remaining 6 were processed for immunohistochemistry (against IL-17A and GFAP, Iba1, NeuN, and CD3). RESULTS: The ELISA study data showed a significant increase in IL-17A concentrations in the 7-, 15-, 30-, and 60-day exposure groups, with regard to the control group (P<.05). Furthermore, they indicate that hippocampal neurons were the cells showing greatest immunoreactivity against IL-17A between 60 and 90 days of exposure to ozone; we also observed an increase in activated astrocytes in the 30- and 60-day exposure groups. CONCLUSION: Exposure to ozone in rats induces an increase in IL-17A expression, mainly in hippocampal neurons, accompanied by hippocampal astrocyte activation during chronic neurodegeneration, similar to that observed in Alzheimer disease in humans.

[Obesity, metabolic syndrome and olfactory perception]. / Obesidad, síndrome metabólico y percepción olfativa.

Nowadays, it is well accepted that obesity and metabolic syndrome are diseases that constitute a global public health issue. In consequence, the interest in the study of the effects these pathologies produce in the central nervous system has greatly increased in the last decades. One of the most overlooked topics in the literature is the impact they exert in sensory systems, among which is olfaction. The olfactory system is related to a number of vital functions, like the activation of defense mechanisms, contribution to appetitive and digestive reflexes, recognition of conspecifics, and even has socio-sexual implications. It has been discovered that the olfactory system also plays a crucial role in food intake, the choice of foods, appetite and satiety mechanisms; therefore, it is involved in obesity development. Clinical studies have proven that obese patients exhibit hyposmia more frequently than aged-matched healthy controls. Olfactory alterations have also been found in obese rodents or in animals with similar features of human metabolic syndrome. The causes of this association are still being investigated. This work reviews the studies that have tried to understand this association from a preclinical and clinical approach as well as those biological mechanisms that could be involved. The evidences here presented suggest that obesity and metabolic syndrome affect the adequate function of olfactory sensory system.

TITLE: Obesidad, síndrome metabólico y percepción olfativa.En la actualidad, la obesidad y el síndrome metabólico son enfermedades que representan un grave problema global de salud pública. A consecuencia de ello, en las últimas décadas ha aumentado el interés por estudiar los efectos de estas patologías sobre el funcionamiento del sistema nervioso central. Uno de los aspectos más ignorados en la bibliografía ha sido el impacto que tienen sobre los sistemas sensoriales, entre los que se encuentra el olfato. El sistema olfativo se relaciona con distintas funciones vitales, como activar mecanismos de defensa, contribuir a la inducción de reflejos apetitivos y digestivos, y reconocer individuos de su misma especie, e incluso tiene implicaciones sociosexuales. Se sabe que, además, desempeña un papel importante en la ingesta de alimentos, en la decisión de lo que se va a consumir, en los mecanismos de apetito y saciedad y, por ende, está involucrado en el desarrollo de obesidad. Estudios clínicos han demostrado que pacientes con obesidad presentan hiposmia con mayor frecuencia en comparación con sujetos delgados de la misma edad. También se han encontrado alteraciones en el olfato de roedores que presentan obesidad o rasgos similares a los del síndrome metabólico del humano. Las causas por las cuales existe esta asociación apenas están comenzando a investigarse; en este trabajo se revisan los estudios que han intentado entenderla desde un enfoque clínico y preclínico, así como los mecanismos biológicos que hasta el momento se han explorado en la bibliografía.

Systemic Th17/IL-17A response appears prior to hippocampal neurodegeneration in rats exposed to low doses of ozone. / La respuesta sistémica Th17/IL-17A aparece antes del proceso neurodegenerativo en el hipocampo de ratas expuestas a bajas dosis de ozono.

INTRODUCTION: Exposure to low doses of O3 leads to a state of oxidative stress. Some studies show that oxidative stress can modulate both the CNS and systemic inflammation, which are important factors in the development of Alzheimer disease (AD). OBJECTIVE: This study aims to evaluate changes in the frequency of Th17-like cells (CD3+CD4+IL-17A+), the concentration of IL-17A in peripheral blood, and hippocampal immunoreactivity to IL-17A in rats exposed to low doses of O3. METHODS: One hundred eight male Wistar rats were randomly assigned to 6 groups (n=18) receiving the following treatments: control (O3 free) or O3 exposure (0.25ppm, 4hours daily) over 7, 15, 30, 60, and 90 days. Twelve animals from each group were decapitated and a peripheral blood sample was taken to isolate plasma and mononuclear cells. Plasma IL-17A was quantified using LUMINEX, while Th17-like cells were counted using flow cytometry. The remaining 6 rats were deeply anaesthetised and underwent transcardial perfusion for immunohistological study of the hippocampus. RESULTS: Results show that exposure to O3 over 7 days resulted in a significant increase in the frequency of Th17-like cells and levels of IL-17A in peripheral blood. However, levels of Th17/IL-17A in peripheral blood were lower at day 15 of exposure. We also observed increased IL-17A in the hippocampus beginning at 30 days of exposure. CONCLUSION: These results indicate that O3 induces a short-term, systemic Th17-like/IL-17A effect and an increase of IL-17A in the hippocampal tissue during the chronic neurodegenerative process.

Effect of exposure to low doses of ozone on interleukin 17A expression during progressive neurodegeneration in the rat hippocampus. / Efecto de la exposición a bajas dosis de ozono en la expresión de la interleucina 17A durante el proceso de neurodegeneración progresiva en el hipocampo de ratas.

INTRODUCTION: Chronic exposure to low doses of ozone causes oxidative stress and loss of regulation of the inflammatory response, leading to progressive neurodegeneration. OBJECTIVE: We studied the effect of chronic exposure to low doses of ozone on IL-17A concentration and expression in neurons, microglia, astrocytes, and T cells in the rat hippocampus. METHODS: We used 72 Wistar rats, divided into 6 groups (n=12): a control group (no ozone exposure) and 5 groups exposed to ozone (0.25ppm, 4h daily) for 7, 15, 30, 60, and 90 days. We processed 6 rats from each group to quantify IL-17A by ELISA; the remaining 6 were processed for immunohistochemistry (against IL-17A and GFAP, Iba1, NeuN, and CD3). RESULTS: The ELISA study data showed a significant increase in IL-17A concentrations in the 7-, 15-, 30-, and 60-day exposure groups, with regard to the control group (P<.05). Furthermore, they indicate that hippocampal neurons were the cells showing greatest immunoreactivity against IL-17A between 60 and 90 days of exposure to ozone; we also observed an increase in activated astrocytes in the 30- and 60-day exposure groups. CONCLUSION: Exposure to ozone in rats induces an increase in IL-17A expression, mainly in hippocampal neurons, accompanied by hippocampal astrocyte activation during chronic neurodegeneration, similar to that observed in Alzheimer disease in humans.