Microcystin‐LR disrupts insulin signaling by hyperphosphorylating insulin receptor substrate 1 and glycogen synthase

Self Cite

Our previous work indicated exposure of Human liver cell 7702 (HL7702) cells to Microcystin-leucine-arginine (MC-LR) for 24 hours can disrupt insulin (INS) signaling by the hyperphosphorylation of specific proteins. For further exploring the timedependent effect posed by MC-LR on this pathway, in the current study, HL7702 cells together with mice were exposed to the MC-LR with different concentrations under short-term treatment, and then, protein phosphatase 2A (PP2A) activity and expression of proteins related to INS signaling, as well as the characteristics of their action in the liver, were investigated. The results indicated, in HL7702 cells with 0.5, 1, and 6 hours of treatment by MC-LR, PP2A activity showed an obvious decrease in a time and concentration-dependent manner. While the total protein level of Akt, glycogen synthase kinase 3 (GSK-3), and glycogen synthase remained unchanged, GSK-3 and Akt phosphorylation increased significantly. In livers of mice with 1 hour of intraperitoneal injection with MC-LR, a similar change in these proteins was observed. In addition, the levels of total IRS1 and p-IRS1 at serine sites showed decreasing and increasing trends,respectively, and the hematoxylin and eosin staining showed that liver tissues of mice in the maximum-dose group exhibited obvious hepatocyte degeneration and hemorrhage. Our results further proved that short-term treatment with MC-LR can inhibit PP2A activity and disrupt INS signaling proteins' phosphorylation level, thereby interfering with the INS pathway. Our findings provide a helpful understanding of the toxic effects posed by MC-LR on the glucose metabolism of liver via interference with the INS signaling pathway. K E Y W O R D S INS signaling proteins, microcystin-LR, PP2A, short-term treatment 1 | INTRODUCTION Microcystin (MC) refers to a group of monocyclic heptapeptides toxins generated via cyanobacteria and are largely released in waterbodies where cyanobacteria bloom occurs. The increased occurrence of cyanobacteria bloom due to eutrophication emphasizes the need for studying the toxic effects posed by MCs on humans and animals. To date, over 90 various structural analogues of the MC have been documented, there into, Microcystin-leucine-arginine (MC-LR) exhibits a wide distribution and strong toxicity in the MC family. 1 MC-LR is a highly liverspecific toxin and can induce generalized hepatocyte degeneration in case of chronic poisoning, leading to progressive fibrosis, necrosis, as well as infiltration of mononuclear leukocyte, 2 while as to its acute poisoning, MC-LR can disorganize the hepatic architecture rapidly, break Pu Huang and Kele Chen are the co-first authors.

Section: Discussionsupporting

confidence: 87%

Section: Discussionsupporting

confidence: 80%

Section: Discussionmentioning

confidence: 69%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The effects of short‐term treatment of microcystin‐LR on the insulin pathway in both the HL7702 cell line and livers of mice

Huang

Chen

et al. 2020

Self Cite

Microcystin‐LR exposure disrupts the insulin signaling pathway in C2C12 mice muscle cell line

Cao

Chen

et al. 2019

Microcystin‐LR (MC‐LR) is a widely produced monocyclic heptapeptides in eutrophication waterbodies. MC‐LR can induce various toxic effects in different cells. Our previous studies have found that MC‐LR exposure can disrupt insulin signaling pathway in human liver cells (HL 7702). Skeletal muscle is one of the major organs for glucose disposal and responsive to insulin. However, the effects of MC‐LR on insulin signaling pathway in muscle cells have not been fully explored. By using C2C12 mice muscle cells, this study aims to investigate the toxic effects of MC‐LR in muscle cells with a focus on its effects on insulin signaling pathways. It was found that MC‐LR entered into cells and inhibited protein phosphatase 2A (PP2A) significantly. Furthermore, MC‐LR increased phosphorylation of Ser302, Ser307, Ser612 of insulin receptor substrate 1, AKT‐Ser473, GSK3α‐Ser21, and S6K1‐Thr389 by inhibiting the activity of PP2A. The results in this study demonstrate that exposure of MCLR can disrupt the insulin pathway in muscle cells.

PI3K/AKT/mTOR pathway mediated‐cell cycle dysregulation contribute to malignant proliferation of mouse spermatogonia induced by microcystin‐leucine arginine

Liu

Tian

et al. 2022

Environmental cyanotoxin exposure may be a trigger of testicular cancer. Activation of PI3K/AKT/mTOR signaling pathway is the critical molecular event in testicular carcinogenesis. As a widespread cyanotoxin, microcystin-leucine arginine (MC-LR) is known to induce cell malignant transformation and tumorigenesis. However, the effects of MC-LR on the regulatory mechanism of PI3K/AKT/mTOR pathway in seminoma, the most common testicular tumor, are unknown. In this study, mouse spermatogonia cell line (GC-1) and nude mice were used to investigate the effects and mechanisms of MC-LR on the malignant transformation of spermatogonia by nude mouse tumorigenesis assay, cell migration invasion assay, western blot, and cell cycle assay, and so forth. The results showed that, after continuous exposure to environmentally relevant concentrations of MC-LR (20 nM) for 35 generations, the proliferation, migration, and invasion abilities of GC-1 cells were increased by 120%, 340%, and 370%, respectively. In nude mice, MC-LR-treated GC-1 cells formed tumors with significantly greater volume (0.998 ± 0.768 cm 3 ) and weight (0.637 ± 0.406 g) than the control group (0.067 ± 0.039 cm 3 ; 0.094 ± 0.087 g) (P < .05). Furthermore, PI3K inhibitor Wortmannin inhibited the PI3K/AKT/mTOR pathway and its downstream proteins (c-MYC, CDK4, CCND1, and MMP14) activated by MC-LR.Blocking PI3K alleviated MC-LR-induced cell cycle disorder and malignant proliferation, migration and invasive of GC-1 cells. Altogether, our findings suggest that MC-LR can induce malignant transformation of mouse spermatogonia, and the PI3K/ AKT/mTOR pathway-mediated cell cycle dysregulation may be an important target for malignant proliferation. This study provides clues to further reveal the etiology and pathogenesis of seminoma.