*Article* **Protective Effects of** *Ulva lactuca* **Polysaccharide Extract on Oxidative Stress and Kidney Injury Induced by D-Galactose in Mice**

**Qian Yang 1, Yanhui Jiang 2, Shan Fu 1, Zhaopeng Shen 3,\*, Wenwen Zong 2, Zhongning Xia 4, Zhaoya Zhan <sup>5</sup> and Xiaolu Jiang 1,2,6,\***


**Abstract:** Reactive oxygen species (ROS) are the key factors that cause many diseases in the human body. Polysaccharides from seaweed have been shown to have significant antioxidant activity both in vivo and in vitro. The ameliorative effect of *Ulva lactuca* polysaccharide extract (UPE) on renal injury induced by oxidative stress was analyzed. As shown by hematoxylin–eosin staining results, UPE can significantly improve the kidney injury induced by D-galactose (D-gal). Additionally, the protective mechanism of UPE on the kidney was explored. The results showed that UPE could decrease the levels of serum creatinine (Scr), blood urea nitrogen (BUN), serum cystatin C (Cys-C), lipid peroxidation, protein carbonylation, and DNA oxidative damage (8-OHdG) and improve kidney glutathione content. Moreover, UPE significantly increased the activities of superoxide dismutase and glutathione peroxidase and total antioxidant activity in mice. UPE also decreased the levels of inflammatory cytokines TNF-α and IL-6. Further investigation into the expression of apoptotic protein caspase-3 showed that UPE decreased the expression of apoptotic protein caspase-3. These results indicate that UPE has a potential therapeutic effect on renal injury caused by oxidative stress, providing a new theoretical basis for the treatment of oxidative damage diseases in the future.

**Keywords:** *Ulva lactuca*; polysaccharide; D-galactose; oxidative stress; kidney
