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Nitric oxide (NO) is an important signaling molecule involved in many physiological processes in plants. Nitric oxide generation and flavonoid accumulation are two early reactions of plants to ultraviolet-B (UV-B) irradiation. However, the source of UV-B-triggered NO generation and the role of NO in UV-B-induced flavonoid accumulation are not fully understood. In order to evaluate the origin of UV-B-triggered NO generation, we examined the responses of nitrate reductase (NR) activity and the expression levels of NIA1 and NIA2 genes in leaves of Betula pendula Roth (silver birch) seedlings to UV-B irradiation. The data show that UV-B irradiation stimulates NR activity and induces up-regulation of NIA1 but does not affect NIA2 expression during UV-B-triggered NO generation. Pretreatment of the leaves with NR inhibitors tungstate (TUN) and glutamine (Gln) abolishes not only UV-B-triggered NR activities but also UV-B-induced NO generation. Furthermore, application of TUN and Gln suppresses UV-B-induced flavonoid production in the leaves and the suppression of NR inhibitors on UV-B-induced flavonoid production can be reversed by NO via its donor sodium nitroprusside. Together, the data indicate that NIA1 in the leaves of silver birch seedlings is sensitive to UV-B and the UV-B-induced up-regulation of NIA1 may lead to enhancement of NR activity. Furthermore, our results demonstrate that NR is involved in UV-B-triggered NO generation and NR-mediated NO generation is essential for UV-B-induced flavonoid accumulation in silver birch leaves.

Eriodictyol, a flavonoid present in citrus fruits, has been reported to have antioxidant and anti-inflammatory effects. In this study, the protective effects of eriodictyol on cisplatin (CP)-induced kidney injury were detected. CP-induced kidney injury model was established by administration of CP (20 mg/kg). The results showed that treatment of eriodictyol inhibited the production of blood urea nitrogen (BUN), creatinine, MDA, TBARS, reactive oxygen species (ROS), as well as the production of TNF-α, and IL-1β in kidney tissues induced by CP. Eriodictyol also up-regulated the activities of SOD, CAT, and GSH-PX decreased by CP. Furthermore, eriodictyol was found to up-regulate the expression of Nrf2/HO-1 and inhibited CP-induced NF-κB activation in kidney tissues. In conclusion, eriodictyol protected against CP-induced kidney injury through activating Nrf2 and inhibiting NF-κB activation. [ABSTRACT FROM AUTHOR]