Scorpion Venom Peptides Enhance Immunity and Survival in Litopenaeus vannamei Through Antibacterial Action Against Vibrio parahaemolyticus

Ling Zeng ^1,2 Yulin Sun ³ Hualin Zhang ² Xiangxi Yi ⁴ Ran Du ⁴ Ziming Chen ^2* Qi Wang ^5*

• ¹ Lingnan Normal University, Zhanjiang, China
• ² School of Chemistry and Chemical Engineering, Lingnan Normal University, Zhanjiang, Guangdong Province, China
• ³ Life Science & Technology School, Lingnan Normal University, Zhanjiang, Guangdong Province, China
• ⁴ Guangxi Key Laboratory of Marine Drugs, Guangxi University of Chinese Medicine, Nanning, Guangxi Zhuang Region, China
• ⁵ Shenzhen Institute of Guangdong Ocean University, Guangdong Ocean University, Shenzhen, China

A series of 13-amino-acid peptides derived from scorpion venom, specifically Bmkn1, Bmkn2, and Bmkn2-7, were characterized and their biological activities were analyzed. These peptides were characterized by their amphipathic alpha-helical structures, each possessing distinct net charges and hydrophobic properties. Investigations into their antibacterial mechanisms revealed that these peptides significantly enhance the permeability of both the inner and outer membranes of Vibrio parahaemolyticus (VP), increase membrane depolarization, elevate the levels of reactive oxygen species (ROS) within VP cells, and reduce ATPase activity. Bmkn2-7 exhibits superior outer membrane penetration and depolarization capabilities, whereas Bmkn1 demonstrates greater efficacy in disrupting the inner membrane and inducing ROS accumulation.Challenge experiments further indicated that all three peptides significantly improved the survival rate of Litopenaeus vannamei infected with Vibrio parahaemolyticus (P < 0.01), with Bmkn1 and Bmkn2-7 showing markedly more pronounced effects compared to Bmkn2. Additionally, these peptides effectively modulated immune enzyme activity, enhancing the immune response in L. vannamei. Following infection, treatment with these peptides resulted in a significant increase in phenoloxidase (PO) activity and complement component 3 (C3) levels (P < 0.05). Furthermore, there was a marked reduction in the expression levels of inflammatory factors TNF-α, IL-1β, and TGF-β, along with a significant decrease in the expression of antimicrobial peptide genes ALF and Crus (P < 0.001). The expression of apoptosis-related factors, including Cyt-c, Bax, Caspase-3, Caspase-8, and P53, was also significantly downregulated (P < 0.001), contributing to the alleviation of the inflammatory response. In terms of immune regulation, the three peptides exhibited slight variations in their effects. In summary, Bmkn1, Bmkn2, and Bmkn2-7 significantly disrupted the physiological functions of VP, markedly enhancing the survival rates of L. vannamei, stimulating immune enzyme activity, and attenuating inflammatory responses following VP infection. The peptides can be ranked in efficacy as follows: Bmkn2-7 ≈ Bmkn1 > Bmkn2.