Neuregulin 1-Βeta Cytoprotective Role in AML 12 Mouse Hepatocytes Exposed to Pentachlorophenol

Abstract

Neuregulins are a family of growth factor domain proteins that are structurally related to the epidermal growth factor. Accumulating evidence has shown that neuregulins have cyto- and neuroprotective properties in various cell types. In particular, the neuregulin-1 βeta (NRG1-β) isoform is well documented for its anti-inflammatory properties in rat brain after acute stroke episodes. Pentachlorophenol (PCP) is an organochlorine compound that has been widely used as a biocide in several industrial, agricultural, and domestic applications. Previous investigations from our laboratory have demonstrated that PCP exerts both cytotoxic and mitogenic effects in human liver carcinoma (HepG2) cells, primary catfish hepatocytes and AML 12 mouse hepatocytes. We have also shown that in HepG2 cells, PCP has the ability to induce stress genes that may play a role in the molecular events leading to toxicity and tumorigenesis. In the present study, we hypothesize that NRG1-β will exert its cytoprotective effects in PCP-treated AML 12 mouse hepatocytes by its ability to suppress the toxic effects of PCP. To test this hypothesis, we performed the MTT-cell respiration assay to assess cell viability, and Western-blot analysis to assess stress-related proteins as a consequence of PCP exposure. Data obtained from 48 h-viability studies demonstrated a biphasic response; showing a dose-dependent increase in cell viability within the range of 0 to 3.87 μg/mL, and a gradual decrease within the concentration range of 7.75 to 31.0 μg/mL in concomitant treatments of NRG1-β+PCP and PCP. Cell viability percentages indicated that NRG1-β+PCP-treated cells were not significantly impaired, while PCP-treated cells were appreciably affected; suggesting that NRG1-β has the ability to suppress the toxic effects of PCP. Western Blot analysis demonstrated the potential of PCP to induce oxidative stress and inflammatory response (c-fos), growth arrest and DNA damage (GADD153), proteotoxic effects (HSP70), cell cycle arrest as consequence of DNA damage (p53), mitogenic response (cyclin-D1), and apoptosis (caspase-3). NRG1-β exposure attenuated stress-related protein expression in PCP-treated AML 12 mouse hepatocytes. Here we provide clear evidence that NRG1-β exerts cytoprotective effects in AML 12 mouse hepatocytes exposed to PCP.

2,4‐dichlorophenol induces ER stress‐mediated apoptosis via eIF2α dephosphorylation in vitro

“…The decrease of MMP caused the release of pro‐apoptotic proteins from the mitochondria leading to caspases activation, and the caspase‐3 as a key executor of apoptosis was activated by many exogenous toxicants. Our study showed that 2,4‐DCP exposure elevated the activity of caspase‐3 in a time‐dependent manner, which is consistent with the results on human lymphocytes exposed to 2,4,5‐trichlorophenol (Michalowicz and Sicinska, ) and on mouse hepatocytes treated by pentachlorophenol (Dorsey et al, ), indicating that the activation of caspase‐3 is also a critical molecular event in 2,4‐DCP‐induced apoptosis. Based on these findings, we proposed that 2,4‐DCP could collapse MMP, activate caspase‐3, and ultimately lead to apoptosis in vitro .…”

2,4,6-Trichlorophenol Cytotoxicity Involves Oxidative Stress, Endoplasmic Reticulum Stress, and Apoptosis

“…50,51 Induction of CHOP by 2,4,6-TCP led us to ask whether 2,4,6-TCP could induce apoptosis. Previous studies have demonstrated that caspase 3 activation was involved in 2,4,5-trichlorophenol and pentachlorophenol-induced apoptosis in human lymphocytes 33 and mouse hepatocytes, 52 respectively. These findings revealed that caspase 3 is a critical player in CPs-induced apoptosis.…”

Pentachlorophenol decreases ATP levels in human natural killer cells

“…A number of previous studies have shown that oxidative metabolites of PCP are responsible for some of its toxic effects in rodents (Dorsey et al, 2006; Umemura et al, 2006; 2003; Wang et al, 2001). Additionally, PCP has effects similar to butyltin (BT) compounds on NK lytic function and ATP levels (Whalen et al 1999; Dudimah et al 2007a,b) and glutathione and other sulfhydryl containing compounds have been shown to reverse the negative effects of BT compounds on ATP (Cain et al, 1977).…”

“…This data will allow us to determine if PCP is able to interfere with ATP production in NK cells and whether any interference is associated with loss of NK lytic function. Additionally, we examined whether the antioxidants, vitamin E or reduced glutathione, were able to reverse the negative effects of PCP on lytic function and/or ATP levels, as there has been evidence in rodents (Dorsey et al, 2006; Umemura et al, 2006; 2003) and in human hepatoma cell lines (Wang et al, 2001) and human liver cell microsomes (Juhl et al, 1985) that PCP oxidative metabolism is important in its toxic effects in those systems.…”