Neuroprotective effects of thymoquinone against cerebellar histopathological changes in propylthiouracil-induced hypothyroidism in adult rats

Purpose: To evaluate the effects of thymoquinone (TQ) on histological and immunohistochemical changes in the cerebellar cortex induced by propylthiouracil (PTU) treatment in rats.
Methods: Thirty-two adult male albino rats were randomly divided into four groups: C, control; PTU, treatment with oral PTU to induce hypothyroidism; TQ, treatment with TQ; and PTU + TQ, concomitant treatment with oral PTU and TQ for 6 weeks. Cavalieri’s principle and physical dissector methods were employed for unbiased deduction of cerebellar granular layer volume, numerical density, and number of granular cells.
Results: In the PTU group, hematoxylin and eosin (H&E)-stained sections revealed degeneration of Purkinje cells, neuronal loss, and spongiosis in the white matter. A decrease in the number of astrocytes-expressing glial fibrillary acidic protein (GFAP) and a significant decrease in granular layer cell density were also seen. Concomitant administration of TQ ameliorated histopathological changes, increased the proportion of GFAP-positive astrocytes, increased granular cell density, and significantly (p < 0.05) increased the levels of thyroid-stimulating hormones, T3 and T4.
Conclusion: TQ treatment significantly decreases cerebellar changes resulting from PTU-induced hypothyroidism, and results in the retention of neuronal structural integrity in the cerebellar cortex.

Keywords
Hypothyroidism; Cerebellum; Thymoquinone; Stereology; Glial fibrillary acidic protein; Neuronal structural integrity