Midkine secretion protects Hep3B cells from cadmium induced cellular damage

Abstract

Aim: To evaluate role of midkine secretion during Cadmium (Cd) exposure in the human hepatocyte cell line Hep3B cells.

Methods: Different dosages of Cd (0.5-1-5-10 microg/mL) were applied to Hep3B cells and their effects to apoptosis, lactate dehydrogenase (LDH) leakage and midkine secretion were evaluated as time dependent manner. Same experiments were repeated with exogenously applied midkine (250-5000 pg/mL) and/or 5 microg/mL Cd.

Results: Cd exposure induced prominent apoptosis and LDH leakage beginning from lower dosages at the 48th h. Cd induced midkine secretion with higher dosages (P < 0.001), (control, Cd 0.5-1-5-10 microg/mL respectively: 1123 +/- 73, 1157 +/- 63, 1242 +/- 90, 1886 +/- 175, 1712 +/- 166 pg/mL). Exogenous 500-5000 pg/mL midkine application during 5 microg/mL Cd toxicity prevented caspase-3 activation (control, Cd toxicity, 250, 500, 1000, 2500, 5000 pg/mL midkine+ Cd toxicity, respectively: 374 +/- 64, 1786 +/- 156, 1545 +/- 179, 1203 +/- 113, 974 +/- 116, 646 +/- 56, 556 +/- 63 cfu) LDH leakage and cell death in Hep3B cells (P < 0.001).

Conclusion: Our results showed that midkine secretion from Hep3B cells during Cd exposure protects liver cells from Cd induced cellular damage. Midkine has anti-apoptotic and cytoprotective role during Cd toxicity. Further studies are needed to explain the mechanism of midkine secretion and cytoprotective role of midkine during Cd exposure. Midkine may be a promising therapeutic agent in different toxic hepatic diseases.

Figure 1

Cell death (%) was determined at 2^nd, 24^th and 48^th h by the MTT assay. Cd exposure induced prominent cell death in Hep3B hepatocytes with dose and time dependent manner. Data are from 6 independent experiments for each condition. Data are presented as mean ± SEM. ^bP < 0.001 vs control group.

Figure 2

Cell number (%) was determined by MTT assay following 2^nd, 24^th and 48^th h exposure to 250-5000 pg/mL and/or 5 μg/mL Cd. Midkine treatment increased cell proliferation in Hep3B hepatocytes with dose and time dependent manner. Data are presented as mean ± SEM.

Figure 3

Caspase-3 levels were measured following a 48 h exposure to 0.5-10 μg/mL Cd. Data were given as mean ± SEM. ^bP < 0.001 vs control group.

Figure 4

Caspase-3 levels were measured following a 48 h of exposure to 250-5000 pg/mL Midkine and/or 5 μg/mL Cd. Data are presented as mean ± SEM. ^bP < 0.001 vs control group.

Figure 5

Cd induced cytotoxicity at the 48^th h of experiment determined by % LDH released to medium. Starting from the 1 μg/mL dosage Cd treatment caused prominent LDH release from hepatocytes at the end of 48^th h (P < 0.001). Data are presented as mean ± SEM. ^bP < 0.001 vs control group.

Figure 6

Effects of 48 h midkine (250-5000 pg/mL) and/or 5 μg/mL Cd treatment on the LDH leakage in the Hep3B cells. Data are presented as mean ± SEM. ^bP < 0.001 vs control group.

Figure 7

Effects of 0.5-10 μg/mL Cd treatment on midkine secretion in the Hep3B cells. With 0.5 and 1 μg/mL Cd exposure we obtained similar midkine secretion as untreated cells. Midkine secretion was highest as a response to 5 μg/mL Cd treatment dosage. Data are presented as mean ± SEM. ^bP < 0.001 vs control group.