Page 165 - 《水产学报》2023年第1期

李谣，等 水产学报, 2023, 47(1): 019611

Effects of hypoxia stress and reoxygenation on appetite, hypoxic response
genes and physiological and biochemical indexes in
the brain tissues of Leiocassis longirostris

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LI Yao , YANG Zhiru , CHENG Jinghao , LI Jie , NING Xianhui , WANG Tao ,
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ZHANG Kai , JI Jie , ZHANG Guosong , YIN Shaowu 1*
(1. Jiangsu Province Engineering Research Center for Aquatic Animals Breeding and Green Efficient Aquacultural Technology,
College of Marine Science and Engineering, Nanjing Normal University, Nanjing 210023, China;
2. Heze University, Key Laboratory of Physiology, Biochemistry and Application in Universities of
Shandong Province during the 13th Five-Year Plan, Heze 274015, China)
Abstract: Affected by natural factors such as temperature, season and weather, or human factors such as eutroph-
ication and high stocking density, oxygen concentration in the water environment where fish live is unpredictable,
and they are often faced with a low-oxygen environment. Studies have found that fish have evolved a complex
physiological and biochemical system to adapt to the stress response caused by hypoxia in the water environment.
However, severe and acute hypoxia can cause a large number of fish to suffocate and die in a short period of time.
Because of its delicious taste, no intermuscular spines and high nutritional value, the L. longirostris has become
one of the important freshwater aquaculture species in China. Currently, studies have been carried out at home and
abroad on the growth characteristics, product processing and nutritional evaluation of this fish. There are few
reports on its important ecological impact factor "hypoxia". In order to understand the regulatory mechanism of the
brain tissue in response to hypoxic stress. In this study, enzyme activity determination, H.E staining, qRT-PCR,
TUNEL detection and other methods were used. Changes in brain tissue of L. longirostris hypoxia response genes,
physiological and biochemical indicators and appetite genes were analyzed and compared under hypoxic stress
[(0.8±0.1) mg/L] 0, 2, 4 and 6 hour (labeled as H0, H2, H4 and H6) and recovery [(7.3±0.5) mg/L] 2,4 and 6 hour
(labeled as R2, R4 and R6). The results showed that: Under hypoxic stress and recovery, the expression levels of
oxygen-sensing protein-related genes (HIFs, PHDs and Vhl) in the brain tissue of L. longirostris showed a trend of
first rising and then falling as a whole. Respiratory metabolic enzymes (HK, PK and LDH) activities were signific-
antly increased at H0, SDH and MDH activities were significantly reduced at H6. After reoxygenation, the meta-
bolic mode gradually changes from anaerobic respiration to aerobic respiration. Antioxidative enzymes (GSH-Px,
CAT and SOD) and stress indicators (MDA and LPO) gradually increased after 2 h of hypoxia, and oxidative
stress persists after the recovery of dissolved oxygen. Through the observation of brain tissue morphology, it was
found that under hypoxia stress, neuronal cell swelling and vacuoles were damaged in the brain tissue of L.
longirostris, which were not effectively improved after 6 hours of reoxygenation with dissolved oxygen. However,
with the prolongation of hypoxia time, the degree of apoptosis of brain tissue cells increased, and the expression of
apoptosis-related genes (Bax, Caspase-3 and p53) increased significantly, while the expression of Bcl-2 gene
decreased, there are still significant differences in expression compared with the control group after the recovery of
dissolved oxygen. In addition, it was found that the feeding rate of L. longirostris decreased by 54% and 98% at 0
h and 2 h of hypoxia stress, respectively. Hypoxic stress was detected to significantly inhibit the expression of
appetite-promoting genes (NPY) and inducible food-suppressive genes (PYY, CCK and NUCB2). This experiment
showes that hypoxic stress and reoxygenation have significant effects on oxygen sensor proteins, respiratory meta-
bolism, oxidative stress, structural morphology, apoptosis and appetite in the brain tissues of L. longirostris. The
results of this study provide a theoretical basis for elucidating the molecular regulation mechanism of L.
longirostris brain tissues under hypoxia stress and reoxygenation, it has guiding significance for the intensive and
healthy breeding of this fish and the selection and breeding of new hypoxia-tolerant species in the future.
Key words: Leiocassis longirostris; hypoxia stress; brain tissue; hypoxic response gene; appetite
Corresponding authors: ZHANG Guosong. E-mail: zhangguosong@hezeu.edu.cn;
YIN Shaowu. E-mail: yinshaowu@163.com
Funding projects: The “JBGS” Project of Seed Industry Revitalization in Jiangsu Province (JBGS[2021]034) ;
Supported by the National Natural Science Foundation of China (32102754, 32102760); Postgraduate Research &
Practice Innovation Program of Jiangsu Province (SJCX22_0605)

中国水产学会主办 sponsored by China Society of Fisheries https://www.china-fishery.cn
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