Histological and immunohistochemical study on the possible ameliorating effects of thymoquinone on the salivary glands of rats with experimentally induced hypothyroidism

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Abstract

Background

Although the physiological and biochemical effects of hypothyroidism on salivary glands were frequently studied in previous research, its histological aspects have not been sufficiently studied.

Aim

This study aimed to assess the histopathological changes caused by experimentally induced hypothyroidism in rat salivary glands as well as its effect on the antioxidant status, and assess the possible ameliorating effect of thymoquinone (TQ).

Materials and methods

Forty adult male Wister rats were randomly divided into four groups (n=10): control group, TQ-treated group, propylthiouracil-induced hypothyroid group, and TQ-treated hypothyroid group. Thyroid hormone levels, thyroid stimulating hormone levels, and antioxidant status were assessed in the blood. The submandibular, parotid, and sublingual salivary glands were processed for histopathological assessment using routine and immunohistochemical assessment of α-smooth muscle actin, epidermal growth factor, caspase-3, and p53 antibodies.

Results

Salivary gland acini of the hypothyroid rats appeared smaller, and some were atrophied, with significantly increased percentage and number of heterochromatic nuclei and mast cells compared with controls. Increased α-smooth muscle actin and caspase immunoexpression as well as p53-positive cells were evidence of parenchymal injury to the salivary glands. TQ could alleviate these histopathologic changes mostly because of its antioxidant activity as it significantly reduced malondialdehyde, glutathione, and superoxide dismutase activity and significantly increased nitric oxide concentration in hypothyroid rats.

Conclusion

Propylthiouracil-induced hypothyroidism in rats was associated with histological, biochemical, and immunohistochemical changes in the salivary glands, and TQ can alleviate these changes by improving the antioxidant status of the hypothyroid rats. This calls for further confirmation and validation in applied clinical studies on hypothyroid patients.

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