Abstract Although enormous achievements have been made in targeted molecular therapies against hepatocellular carcinoma (HCC), the treatments can only prolong the life of patients with extrahepatic metastases. We evaluated thymoquinone (TQ), a compound from Nigella sativa Linn., for its anti‐cancer effect on SK‐Hep1 cells and HCC‐xenograft nude mice. TQ effectively triggered cell death and activated p38 and extracellular signal‐regulated kinases (Erk) pathways up to 24 h after treatment in cells. TQ‐induced cell death was reversed by p38 inhibitor; however, it was enhanced by si‐Erk. The caspase3 activation and TUNEL assay revealed a stronger toxic effect upon co‐treatment with TQ and si‐Erk. Our study suggested that phosphorylation of p38 in SK‐Hep1 cells constituted the major factor leading to cell apoptosis, whereas phosphorylation of Erk led to drug resistance. Furthermore, TQ therapeutic effect was improved upon Erk inhibition in HCC‐xenograft nude mice. TQ could present excellent anti‐HCC potential under suitable p‐Erk inhibiting conditions.
7,12-Dimethylbenz(a)anthracene (DMBA) is a potent carcinogen that induces immunosuppression of both humoral and cell-mediated immunity in mice and other species. Previous studies have shown that CYP1B1 is required for bone marrow toxicity produced by DMBA in mice. Therefore, the purpose of these studies was to determine whether CYP1B1 was required for spleen cell immunotoxicity. Female C57BL/6N wild-type (WT) and CYP1B1 knockout (-/-) mice were treated with 0, 17, 50, or 150 mg/kg (cumulative dose) DMBA in corn oil by oral gavage once a day for five days. Several immunotoxicological assays were used to assess the effects of DMBA on systemic immunity. These included the in vitro T-dependent antibody response to sheep red blood cells (SRBC) measured using a direct plaque forming cell (PFC) assay, T- and B-cell mitogenesis induced by Con A and LPS, and nonspecific cell-mediated immunity was evaluated using an NK cytotoxicity assay. In addition, lymphocyte subpopulations were measured by flow cytometry using specific cell surface markers. Following five days of DMBA treatment, the body weights and spleen cell surface markers of the WT and CYP1B1 (-/-) mice showed no significant changes. A decrease in NK activity was found at the 50 mg/kg DMBA dose in WT mice, but not in the CYP1B1 (-/-) mice. Interestingly, at the 150 mg/kg dose of DMBA, CYP1B1 null mice had decreased NK activity, whereas WT mice did not. The SRBC PFC response demonstrated that the IgM antibody response was suppressed by DMBA in WT mice in a dose-dependent manner (significant at 50 and 150 mg/kg). However, there were no changes in the SRBC PFC responses in any DMBA test group in the CYP1B1 (-/-) mice. Similarly, while DMBA suppressed B- and T-cell mitogenesis at the 50 and 150 mg/kg dose levels in C57BL/6N WT mice, no effect was seen in CYP1B1 (-/-) mice. Thus, CYP1B1 appears to be critical for the immunosuppression of DMBA in mice, suggesting a role for bioreactive metabolites in the spleen cell immunotoxicity produced by DMBA.
Benzo(a)pyrene (BaP) is an environmentally prevalent polycyclic aromatic hydrocarbon (PAH) known to produce immunotoxicity in murine and human lymphocytes. Previous studies by our lab have shown that certain BaP metabolites increase intracellular Ca2+ in human and murine lymphocytes. The mechanism by which these BaP metabolites increase Ca2+ may involve src kinase activation and mitochondrial oxidative stress. We have implicated a new pathway of Ca2+ elevation in lymphocytes produced by a novel BaP metabolite, BaP-7,8-dione (7,8-BPQ). This ortho quinone is produced from BaP-7,8-dihydrodiol by aldoketoreductase 1C1 (AKR1C) isoforms in human cells. We have previously shown that 7,8-BPQ increases Ca2+ levels in an in vitro rabbit skeletal muscle sarcoplasmic reticulum (SR) vesicle model via interaction with ryanodine receptors (RyR). In the present study, we found that 7,8-BPQ produced a RyR-dependent rapid increase in intracellular Ca2+ in the Daudi human B cell line. However, other BP-diones including 1,6-, 3,6-, and 6,12-BPQs failed to produce a rapid increase in Ca2+. Instead they produced a late increase in intracellular Ca2+, presumably via a redox-cycling-dependent loss of Ca2+ buffering capacity by mitochondria. Functional RyR were detected in Daudi using a 3H-ryanodine binding assay. The studies were extended to normal human peripheral blood and murine spleen cells, where it was found that 7,8-BPQ rapidly elevated intracellular Ca2+ in B cells and T cells in both species. The Ca2+-elevating effect of 7,8-BPQ was prevented by pretreatment with a high concentration of ryanodine (500 μM). Collectively, these results demonstrate a novel mechanism of Ca2+ elevation by an environmentally relevant metabolite of BaP in murine and human lymphocytes.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)