Alterations of thyroidal status in brain regions and hypothalamo-pituitary-blood-thyroid-axis associated with dopaminergic depletion in substantia nigra and ROS formation in different brain regions after MPTP treatment in adult male mice

17β-Trenbolone Exposure Enhances Muscle Activity and Exacerbates Parkinson's Disease Progression in Male Mice

Parkinson's disease (PD) ranks as the second most prevalent neurodegenerative disorder, and while the neuroprotective effects of estrogen are well-documented, the impact of androgens on neurological disorders remains understudied. The consequences of exposure to 17-trenbolone (17-TB), an environmental endocrine disruptor with androgen-like properties, on the mammalian nervous system have received limited attention. Therefore, in this study, we aimed to investigate the biological effects of 17-TB exposure on PD. In our investigation using the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model, we discovered that 17-TB exposure elevated testosterone hormone levels prevented androgen receptor (AR) reduction, upregulated the expression of muscular dystrophic factors (Atrogin1, MuRF1, Musa1, and Myostatin), improved muscle strength, and enhanced locomotor activity in the open field test. However, it is noteworthy that exposure to 17-TB also led to an upregulation of neuroinflammatory cytokines (NLRP3, IL-6, IL-1α, and IL-1β) in PD mice. Crucially, 17-TB exposure induced downregulation of nigral apoptotic proteins DJ-1 and Bcl-2 while upregulating Bax and Caspase-3 in PD mice. This exacerbated neuronal apoptosis, ultimately intensifying dopaminergic neuronal degeneration and death in the substantia nigra and striatum of PD mice. In conclusion, our findings indicate that while 17-TB mitigates muscle atrophy and enhances motor activity in PD mice, it concurrently exacerbates neuroinflammation, induces neuronal apoptosis, and worsens dopaminergic neuronal death, thereby aggravating the progression of MPTP-induced Parkinsonism. This underscores the importance of considering potential environmental risks in neurodegeneration associated with Parkinson's disease, providing a cautionary tale for our daily exposure to environmental endocrine chemical disruptors.

Perfluorooctane sulfonates induces neurobehavioral changes and increases dopamine neurotransmitter levels in zebrafish larvae

It has been reported that exposure to perfluorooctane sulfonates (PFOS) causes behavioral abnormalities in zebrafish larvae, but the possible mechanisms underlying these changes remain unexplored. In this study, zebrafish embryos (2 h postfertilization, 2-hpf) were exposed to PFOS at different concentrations (0, 0.032, 0.32 and 3.2 mg/L) for 120 h. Developmental endpoints and the locomotion behavior of larvae were evaluated. Reactive oxygen species (ROS) levels, dopamine contents, several genes and proteins related to neurodevelopment and dopamine signaling were examined. Our results indicate that increased ROS levels in the zebrafish larvae heads may be causally associated with neurodevelopment damage. Meanwhile, brain-derived neurotrophic factor (BDNF) and alpha1-Tubulin (α1-Tubulin) protein contents were significantly increased, which may be a compensatory mechanism for the impaired central nervous system. PFOS-induced locomotor hyperactivity was observed in the first light phase and dark phase at the 0.32 and 3.2 mg/L of PFOS. Upregulation of dopamine-related genes tyrosine hydroxylase (th) and dopamine transporter (dat) associated with increased dopamine contents in the 3.2 mg/L of PFOS. In addition, protein expression of TH and DAT were noted at the 0.32 and 3.2 mg/L of PFOS concentrations. Our results suggested that PFOS induces neurobehavioral changes in zebrafish larvae, possibly by perturbing a dopamine signaling pathway. In addition, PFOS induced development damage, such as increased malformation rate and shorter body length.

Association Between Thyroid Diseases and Parkinson's Disease: A Nested Case-Control Study Using a National Health Screening Cohort

BACKGROUND

Although the dopaminergic system is interconnected with the hypothalamic-pituitary-thyroid axis, few studies have explained the causal relationship between thyroid disease and Parkinson's disease (PD).

OBJECTIVE

The goal of this study was to investigate the association between thyroid diseases and PD in Korean residents.

METHODS

The Korean National Health Insurance Service-National Sample Cohort, which includes individuals aged ≥40 years, was assessed from 2002 to 2015. A total of 5,586 PD patients were matched by age, sex, income, and the region of residence with 22,344 control participants at a ratio of 1:4. In the PD and control groups, previous histories of levothyroxine treatment, goiter, hypothyroidism, thyroiditis, and hyperthyroidism were investigated.

RESULTS

The rates of levothyroxine treatment for more than 3 months, hypothyroidism, and hyperthyroidism were higher in the PD group than the control group (3.2%, 3.8%, and 2.8% vs. 2.5%, 2.9%, and 1.9%, respectively, p < 0.05). The adjusted odds ratios (ORs) in model 2, which was adjusted for all potential confounders, for hypothyroidism and hyperthyroidism in the PD group were 1.25 (95% confidence interval (CI) 1.01-1.55, p = 0.044) and 1.37 (95% CI 1.13-1.67, p = 0.002), respectively. In subgroup analyses, the association between hypothyroidism and PD was maintained in men older than 70 years and the association between hyperthyroidism and PD was maintained in women younger than 70 years.

CONCLUSION

Both hyperthyroidism and hypothyroidism were associated with higher risk of PD, particularly for women younger than 70 years and men older than 70 years, respectively.