T3 and curcumin regulates collagen-IV and collagen-VI expression: role in suppression of amyloid-β via TGFβ1-Sp1 signaling in hypothyroid mice brain.

Hypothyroidism has been associated with cognitive disorders and high risk of neurodegenerative disorders like Alzheimer's disease (AD), which is caused by amyloid-β (Aβ) accumulation in brain. The aim of the study is to examine the therapeutic ability of triiodothyronine (T3) and curcumin in regulating two key extracellular matrix proteins (ECM), collagen IV and collagen VI in brain since both drugs have neuroprotective and anti-fibrotic effects. The study further explored the possible role of signaling molecules such as transforming growth factor β1 (TGFβ1) and specificity protein 1 (Sp1) in regulating the effects of T3 and curcumin on Aβ accumulation and ECM protein expression. Experiment was carried on Balb/c mouse model by inducing hypothyroidism with 0.05% PTU followed by treatment of T3, curcumin and a combination of both. The study revealed a significant increase in the expression of collagen IV and VI, along with elevated levels of TGFβ1 and Sp1 signalling proteins, in hypothyroid conditions in response to increased Aβ expression in both the cortex and hippocampus. Western blot and RT-PCR analysis showed that T3 and curcumin treatment downregulate the levels of ECM proteins, the APP gene, Aβ protein, and the signaling factors. The study found that T3 and curcumin treatment downregulates the collagen IV and VI expression by negatively regulating TGFβ1 and Sp1 when expression of APP and Aβ are low. T3 and coadministration of T3 with curcumin more effectively regulate thyroid function and ECM protein expression in both the cortex and hippocampus. Whereas curcumin alone exhibits limited impacts under the experimental conditions in our study, this may due to bioavailability, dosage or treatment duration which need to further investigation. Our results indicate a novel therapeutic approach for understanding Aβ pathology associated with hypothyroidism, emphasizing the potential association between thyroid hormone and nature-based compounds, such as curcumin, in modulating ECM dynamics and neuroprotection.