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Previous studies have shown that irinotecan (CPT‑11) impairs chemotherapy‑induced apoptosis by activating nuclear factor‑κB (NF‑κB) and a number of strategies have been employed to augment chemosensitivity through the suppression of NF‑κB activation. Berberine, a botanical alkaloid, was reported to enhance chemosensitivity to 5‑fluorouracil and doxorubicin by suppressing NF‑κB activation. In the present study, the effect of berberine on CPT‑11‑induced apoptosis was investigated through the inhibition of NF‑κB. Inhibition of NF‑κB activation by p65 small interfering RNA was shown to potentiate apoptosis induced by CPT‑11. Berberine suppressed CPT‑11‑induced NF‑κB activation in a dose‑dependent manner and enhanced chemosensitivity to CPT‑11 by downregulating NF‑κB activation of antiapoptotic genes, c‑IAP1, c‑IAP2, survivin and Bcl‑xL. The current observations indicate that berberine inhibits NF‑κB activation and may be used to enhance CPT‑11‑induced apoptosis in colon cancer.

To investigate the role of pannexin 1 channels in cisplatin-induced apoptosis in I-10 cells and the mechanisms.MTT assay was used to assess the cytotoxicity of cisplatin (DDP) in I-10 cells. Annexin V/PI double staining and Hoechst 33258 fluorescence staining were employed to detect early- and late-stage apoptosis of the cells, respectively. Extracellular ATP level and intracellular IP3 level in the cells were detected using commercial detection kits.I-10 cells exposed to both CBX (a pannexin 1 channel inhibitor) and DDP showed a higher cell viability compared with the cells exposed to DDP alone (P0.01). CBX significantly decreased cisplatin-induced early-stage apoptosis (P0.001) and late-stage apoptosis (P0.01), and cause obvious reductions in extracellular ATP and intracellular IP3 levels during cisplatin-induced apoptosis (P0.05).Pannexin 1 channels participate in cisplatin-induced apoptosis in I-10 cells possibly through the ATP/IP3 pathway.

Panax Notoginseng Saponins (PNS) have been well known to have anti-tumor activity and enhance cytotoxicity of some cancer chemotherapy agents, but the mechanisms underlying these effects are still unknown. This study investigates the effect of PNS on cytotoxicity of cisplatin and the relationship between this effect and the modulation of gap junctions (GJ) function by PNS in a transfected cell line. The cytotoxicity of cisplatin (0.25-1 µg/mL) was increased in the presence of GJ. Inhibition of gap junction by either GJ blocker or interception of Connexin (Cx) expression decreased the cytotoxicity of cisplatin. Increasing GJ function enhanced cytotoxicity of cisplatin, only in the cells with functional GJ. PNS (50-200 µg/mL) significantly enhanced cisplatin cytotoxicity, but this effect required functional gap junctions between the cells. Exposure of the cells to PNS (50-200 µg/mL) for 4 h leads to a significant enhance in dye coupling of GJ in a dose-dependent manner. These results suggest that PNS increases the cytotoxicity of cisplatin through enhancement of GJ activity.

To investigate the effects of inhibiting gap junctional intercellular communication on hypoxia/reoxygenation injury in astrocytes.Primary cultured cerebral cortical astrocytes of neonate rats were divided into normal control group, hypoxia reoxygenation injury group and 18-α-glycyrrhetinic acid and oleamide (gap junctional intercellular channel inhibitors) group. The gap junction intercellular communication was determined by Parachute assay. The viability of astrocyes was detected by MTT assay. The apoptosis of astrocytes were detected with annexin V/PI and Hoechst 33258 staining.Compared with the normal control group, the gap junctional function of astrocytes was increased significantly in ischemia/reperfusion group (P0.01), the surviving fraction of astrocytes decreased significantly (P0.01) and its cell apoptosis ratio increased significantly (P0.01). Compared with the ischemia/reperfusion group, the gap junctional function of astrocytes in18-α-glycyrrhetinic acid and oleamide group decreased significantly (P0.01), the viability of astrocytes increased significantly (P0.01), while cell apoptosis decreased significantly (P0.01).Inhibition of intercellular gap junction has protective effect against hypoxia/reoxygenation injury in astrocytes.

To investigate the effect of sodium valproate, a histone deacetylase inhibitor, on the cytotoxicity of doxorubicin in breast cancer cells.Western blotting was used to assess Cx43 protein expression in breast cancer Hs578T cells exposed to doxorubicin and sodium valproate. MTT assay was used to determine the cytotoxicity of doxorubicin; annexin V/PI double staining and Hochest 33258 fluorescence staining were employed to detect doxorubicin-induced early and late apoptosis, respectively.Western blotting showed that sodium valproate significantly increased Cx43 protein expression in Hs578T cells (P/0.01). The cells exposed to both sodium valproate and doxorubicin showed significantly lowered cell viability compared with the cells exposed to doxorubicin alone (P/0.01). Exposure to both sodium valproate and doxorubicin resulted in significantly increased early and late cell apoptosis rate compared with doxorubicin treatment alone (P/0.01).sodium valproate can significantly enhance the cytotoxicity of doxorubicin and increase doxorubicin-induced apoptosis in breast cancer cells in vitro possibly by enhancing the gap junction function.

Panax Notoginseng Saponins (PNS) have been well known to have anti-tumor activity and enhance cytotoxicity of some cancer chemotherapy agents, but the mechanisms underlying these effects are still unknown. This study investigates the effect of PNS on cytotoxicity of cisplatin and the relationship between this effect and the modulation of gap junctions (GJ) function by PNS in a transfected cell line. The cytotoxicity of cisplatin (0.25-1 µg/mL) was increased in the presence of GJ. Inhibition of gap junction by either GJ blocker or interception of Connexin (Cx) expression decreased the cytotoxicity of cisplatin. Increasing GJ function enhanced cytotoxicity of cisplatin, only in the cells with functional GJ. PNS (50-200 µg/mL) significantly enhanced cisplatin cytotoxicity, but this effect required functional gap junctions between the cells. Exposure of the cells to PNS (50-200 µg/mL) for 4 h leads to a significant enhance in dye coupling of GJ in a dose-dependent manner. These results suggest that PNS increases the cytotoxicity of cisplatin through enhancement of GJ activity.

To observe the influence of Cx26/Cx32 gap junction channel on the antineoplastic effect of etoposide in Hela cervical cancer cells.Fluorescence trace was used to assay the gap junction intercellular communication mediated by Cx26/Cx32 in Hela cells and its functional modulation by the pharmacological agents (oleamide, retinoid acid). A standard colony-forming assay was applied to determine the cell growth-inhibiting effect of etoposide in Hela cells with functional modulation of the gap junction. Hoechst 33258 staining was used to assess the changes in etoposide-induced apoptosis of Hela cells with altered gap junction functions.Oleamide markedly decreased while retinoid acid obviously increased the gap junction function in Hela cells. Standard colony-forming assay showed that etoposide produced a lowered antiproliferative effect in Hela cells with reduced gap junction and an increased antiproliferative effect in cells with enhanced gap junction function. In cells with a reduced gap junction function, etoposide induced a lowered apoptosis rate, which increased obviously in cells with an enhanced gap junction function.The antineoplastic effect of etoposide is reduced in Hela cells with a decreased gap junction intercellular communication mediated by Cx26/Cx32 and is enhanced in cells with an increased gap junction intercellular communication.