Oxidative Stress Caused by Ozone Exposure Induces Loss of Brain Repair in the Hippocampus of Adult Rats

Abstract

Oxidative stress is involved in many neurodegenerative diseases. Chronic ozone exposure causes a secondary increase of reactive oxygen species, which cause an oxidative stress state in the organism. Ozone is one of the main components of photochemical pollution. Our purpose was to test that oxidative stress caused by chronic low doses of ozone, by itself, alters adult neurogenesis and causes progressive neurodegeneration in the hippocampus, which actions lead to the loss of brain plasticity in the mature central nervous system of rats. Animals were exposed to an ozone-free air stream and for 15, 30, 60, and 90 days to low doses of ozone to cause oxidative stress. Each group was then tested by (1) a spectrophotometer test to quantify lipid peroxidation (LPO) levels; (2) immunohistochemistry testing against doublecortin, Neu-N, p53, microglia, and glial fibrillary acidic protein; (3) Western blot tests for doublecortin and Neu-N; and (4) a one-trial passive avoidance test. Our results indicated that ozone causes an increase of LPO levels, morphological changes in the nucleus and the cytoplasm, and cell swelling in neurons. The Western blot shows a decrease for Neu-N and doublecortin. Activated and later phagocytic microglia and an increased number of astrocytes were found. There was a memory deficiency positively related to the amount of ozone exposure. These alterations suggest that oxidative stress caused by low doses of ozone causes dysregulation of inflammatory processes, progressive neurodegeneration, chronic loss of brain repair in the hippocampus, and brain plasticity changes in the rat analogous to those seen in Alzheimer's disease.

The protective effects of human umbilical cord mesenchymal stem cells on damaged ovarian function: A comparative study

“…An ozone meter (manufactured by Beijing Kang Er Xing Technology Development Co. Ltd., Beijing, China) was used to measure the ozone concentration inside the cage during the experiment. Once the ozonator was turned on, the fresh airflow that entered the ozonator was regulated to maintain the ozone concentration in the center of the cage at 1.2 mg/m 3 (28,29). The mice were exposed to ozone for 8 h (20:00-04:00) each day until the end of the last cycle of superovulation.…”

Free Radicals: Properties, Sources, Targets, and Their Implication in Various Diseases

“…. The regions of the brain such as hippocampus, substantia nigra, and the striatum are particularly susceptible to attack by free radicals [110,111]. The oxidativestress state has been also implicated in several neurodegenerative diseases such as Alzheimer's [112], Parkinson's [113], Huntington's, lateral amyotrophic sclerosis [114], and multiple Sclerosis [115].…”

Oxidative Stress and Neurodegenerative Disease

“…When the inflammatory response is not limited a process of chronic inflammation is established. In the animal model of oxidative stress, caused by exposure to ozone on healthy animals, chronic oxidative stress is able to cause an inflammatory response and dysregulation of the same answer (Rivas-Arancibia et al, 2010). It is widely reported that chronic inflammation produces ROS that lead to a state of oxidative stress.…”

“…High levels of contamination in highly populated cities are correlated with the rise of a number of pathologies, such as autoimmune, degenerative, and neurodegenerative diseases. When using a model of oxidative stress, produced by ozone exposure to low doses (0.25 ppm) for 4 hours daily for different times (7,15,30,60, and 90 days), healthy animals developed a process of progressive neurodegeneration that depends on the exposure time (Angoa-Perez et al, 2006;Pereyra-Muñoz et al, 2006;Rivas-Arancibia et al, 2010, Santiago-Lopez et al, 2010. The increase in the levels of oxidized lipids, proteins, carbohydrates, and nucleic acids are used as indicators of the state of oxidative stress.…”