Inflammation, Dopaminergic Brain and Bilirubin

Dopamine is a well-known neurotransmitter due to its involvement in Parkinson's disease (PD). Dopamine is not only involved in PD but also controls multiple mental and physical activities, such as the pleasure of food, friends and loved ones, music, art, mood, cognition, motivation, fear, affective disorders, addiction, attention deficit disorder, depression, and schizophrenia. Dopaminergic neurons (DOPAn) are susceptible to stressors, and inflammation is a recognized risk for neuronal malfunctioning and cell death in major neurodegenerative diseases. Less is known for non-neurodegenerative conditions. Among the endogenous defenses, bilirubin, a heme metabolite, has been shown to possess important anti-inflammatory activity and, most importantly, to prevent DOPAn demise in an ex vivo model of PD by acting on the tumor necrosis factor-alpha (TNFα). This review summarizes the evidence linking DOPAn, inflammation (when possible, specifically TNFα), and bilirubin as an anti-inflammatory in order to understand what is known, the gaps that need filling, and the hypotheses of anti-inflammatory strategies to preserve dopamine homeostasis with bilirubin included.

Metabolic effects of exposure to pesticides during gestation in female Wistar rats and their offspring: a risk factor for diabetes? Toxicol Res. 2020;36:249-256. [PMID: 32685429 DOI: 10.1007/s43188-019-00028-y]

Some pesticides increase the risk of type 2 diabetes, but whether fetal exposure carries transgenerational risk remains unknown. We evaluated the metabolic effects of gestational exposure to chlorpyrifos and imidacloprid in female Wistar rats and their offspring. We studied female nulliparous Wistar rats, including six exposed to imidacloprid (IMI) and six to chlorpyrifos (CPF) once daily throughout gestation at 1/10 lethal dose 50, while six (control group) received distilled water. These were explored 1 month after the birth of the offspring, while their offspring were explored at weaning (4 weeks) and adult age (12 weeks). Blood glucose, insulin and lipid profile were determined at each stage, while glucose transporter 4 (GLUT4) and nuclear factor kappa beta (NFkβ) protein expression was measured in skeletal muscle at the end of follow up. Exposure to pesticides was associated with significantly higher fasting glucose (+25.4 to 30.9%) and insulin (> 100%) levels, with > 100% increased insulin resistance (HOMA-IR), - 18.3 to - 21.1% reduced HDL-cholesterol and + 60.9 to + 102.6% increased LDL-cholesterol in mothers. GLUT4 expression was reduced by 28.9-42.3% while NFkβ expression increased by 32.8-35.4% in mothers. In offspring, similar abnormalities were observed at weaning (+ 18.4 to 67.4% fasting glucose, + 57.1 to 72.2% LDL-cholesterol, + 72.3 to 78.2% fasting insulin), persisting at adult age with decreased expression of GLUT4 (- 52.8 to 54.5%) and increased expression of NFkβ (+ 30.5 to 30.7%). Gestational exposure to imidacloprid and chlorpyrifos induces hyperglycemia, insulin resistance and dyslipidemia in female Wistar rats and their offspring. The effects on offspring persist until adult age, suggesting intergenerational adverse effects.