Apigenin-mediated Alterations in Viability and Senescence of SW480 Colorectal Cancer Cells Persist in The Presence of L-thyroxine.

INTRODUCTION: Deregulation of Thyroid Hormones (THs) system in Colorectal Cancer (CRC) suggests that these hormones may play roles in CRC pathogenesis. Flavonoids are polyphenolic compounds, which possess potent antitumor activities and interfere, albeit some of them, with all aspects of THs physiology. Whether the antitumor actions of flavonoids are affected by THs is unknown. Therefore, we investigated the effects of apigenin (Api), a well-known flavone, on some tumorigenic properties of SW480 CRC cells in the presence and absence of L-thyroxine (T4). METHODS: Cell viability was assessed by MTT assay. Flow cytometry and DNA electrophoresis were used to evaluate cell death. Cell senescence was examined by in situ detection of ß-galactosidase activity. Protein expression was assessed by antibody array technique. RESULTS: While T4 had minimal effects, Api reduced cell growth and senescence by induction of apoptosis. Expression of anti-apoptotic and pro-apoptotic proteins were differentially affected by Api and T4. Survivin, HSP60 and HTRA were the most expressed proteins by the cells. Almost all Api-induced effects persisted in the presence of T4. CONCLUSION: These data suggest that Api may inhibit CRC cell growth and progression through induction of apoptosis rather than cell necrosis or senescence. In addition, they suggest that T4 has minimal effects on CRC cell growth, and is not able to antagonize the anti-growth effects of Api. Regardless of the treatments, cells expressed high levels of survivin, HSP60 and HTRA, indicating that these proteins may play central roles in SW480 CRC cell immortality.

Differential modulation of claudin 4 expression and myosin light chain phosphorylation by thyroid function in lung injury.

BACKGROUND: Trauma and ventilator-induced lung injury is often associated with endothelial-epithelial barriers breakdown, which may lead to multiple system organ failure (MSOF) and death in critically ill patients. Although molecular mechanism involved in MSOF is not known, junctional opening is believed to happen. In vitro, thyroid hormones inhibit myosin light chain (MLC) phosphorylation and may, thus, inhibit cellular contraction and junctional opening. Trauma is also associated with tissue hypo-thyroid state. Therefore, we examined the effects of thyroid function on expression of phospho-MLC (pp-MLC) and claudin 4 (Clud4), key proteins involved in regulation of junctional tightness, in lung injury. METHODS: Rats were rendered hypo-thyroid (Hypo) or hyperthyroid (Hyper) by adding methimazole or levo-thyroxine, respectively, to their drinking water. Untreated euthyroid (Eue) animals were used as control. Lung pp-MLC and Clud4 proteins were assessed by western blotting and in situ immunodetection, respectively. Lung injury was induced by high tidal volume mechanical ventilation. RESULTS: Lung injury was significantly enhanced in Hypo animals and attenuated in Hyper animals. Parallel changes in expression of lung pp-MLC were detected. Alterations in lung histomorphology correlated with the level of pp-MLC. Expression of alveolar and bronchiolar Clud4 protein was differentially affected by the state of thyroid gland. CONCLUSIONS: Our data suggest that thyroid function plays significant role in lung injury perhaps by modulating expression of the proteins involved in junctional tightness. Besides, they strongly support the idea that the tissue hypo-thyroid state may contribute to endothelial-epithelial barriers breakdown associated with trauma.

Modulation by thyroid hormone of myosin light chain phosphorylation and aquaporin 5 protein expression in intact lung.

Myosin light chain kinase (MLCK) may play a key role in cellular contraction, paracellular permeability and lung water homeostasis. In vitro, thyroid hormones (THs) potently inhibit MLCK activation and, hence, MLC phosphorylation. Whether similar effect is exerted by THs in in vivo systems is not known. Therefore, we investigated the effects of hypothyroid (HO) and hyperthyroid (HR) states on the level of phospho-MLC, aquaporin 5 (AQP5) protein expression, and water holding capacity in the rat lung. Alterations in thyroid state were induced by adding methimazole or levothyroxine (L-T4) to animals' drinking water. Serum TH concentration and thyroid gland histomorphology were assessed to verify the onset of the thyroid state. Lung phospho-MLC and AQP5 proteins were assessed by Western blotting and immunohistochemistry. Lung extravascular water content was estimated by the tissue wet weight-to-dry weight (W/D) ratio. The HO state induced significant increases in the expression of lung phospho-MLC and AQP5 proteins. In contrast, the HR state caused moderate decreases in lung phospho-MLC and AQP5 proteins. While lung water holding capacity was significantly increased in HO animals, it was significantly reduced in HR animals. The data of this study show that THs are able to modulate MLC phosphorylation in in vivo systems. Besides, they suggest that the circulating level of THs may alter lung fluid balance not only through expression of water channels but also through regulation of cellular contraction and paracellular permeability.

Hyperthyroid state or in vitro thyroxine treatment modulates TH1/TH2 responses during exposure to HSV-1 antigens.

Increasingly in recent years, thyroid hormones (THs) have been considered to be important regulators of the immune system. However, their roles in host defense against viral infections are not clearly established. Therefore, this study was undertaken to examine proliferative activity and cytokine production by lymphocytes isolated from hyperthyroid and euthyroid Balb/c mice in response to herpes simplex virus-1 (HSV-1). Lymphocytes of hyperthyroid animals showed a significantly higher rate of proliferation and interferon (IFN)-γ production when compared with that by lymphocytes from euthyroid mice. In vitro thyroxine (T4) treatment was similarly effective in the potentiation of proliferation, but not IFNγ production, by euthyroid lymphocytes. Furthermore, the hyperthyroid state significantly attenuated ConA-, but not HSV-1-, induced interleukin (IL)-10 release; in vitro T4 treatment synergized this effect. These findings suggest that supra-physiologic TH levels (i.e. as occur in hyper-thyroid states) or in vitro TH treatment modulate T-helper (TH)1/TH2 lymphocyte responses and thereby amplifies host defenses against viral infections. One may also conclude that THs may have a potential application in viral immunization and/or treatment of viral infections.