The effect of chloroquine on large yellow croaker (Larimichthys crocea): From autophagy, inflammation, to apoptosis

Abstract

Chloroquine (CQ) is a common autophagy inhibitor but was few understood in marine fish. This study investigated the effects of different concentration of CQ on representative tissues of large yellow croakers (Larimichthys crocea) by setting 5 treatments: 2.52 μg/mL, 5.03 μg/mL, 12.58 μg/mL, 25.16 μg/mL, 50.32 μg/mL, and 251.60 μg/mL CQ groups. We found that the higher the concentration of CQ was, the more obvious the toxic effect it caused, exhibiting as high mortalities of large yellow croakers. The LC50 (24 h) to CQ was 17.14 μg/mL with the upper limit 34.84 μg/mL, the lower limit 8.43 μg/mL, and the standard error 0.16 μg/mL. The CQ treatment also led to the differential expressions of autophagy / inflammation / apoptosis-related genes in representative tissues. The inflammation-related genes IL8 / TNF-α1 (peaked mostly in 2.52 μg/mL and 5.03 μg/mL) and the autophagy-related genes Cx43 / LC3 (from 2.52 μg/mL to 25.16 μg/mL) were more sensitive to lower CQ concentration groups. The apoptosis-related genes BAX / Cas3 were more sensitive to medium CQ concentration (peaked around 25.16 μg/mL). The autophagy and apoptosis-related gene P62 in all tissues peaked in the highest CQ concentration 50.32 μg/mL group, and the expression pattern of P62 was more similar to autophagy genes under Control, but more similar to apoptosis genes in the CQ-treatment groups. In addition, we have newly identified an expression pattern of Cx43 similar to that of the autophagy marker gene LC3, which was also for the first time in marine fish. These data largely enriched our knowledge of the effects of CQ on marine fish and provided a solid basis for further studies on the autophagy regulation in large yellow croakers.