Mitochondrial activity is the key to the protective effect of ß-Lapachone, a NAD+ booster, in healthy cells against cisplatin cytotoxicity.

BACKGROUND: Cisplatin (CDDP) is a first-line chemotherapeutic drug for treating various cancers. However, CDDP also damages normal cells and causes many side effects. Recently, CDDP has been demonstrated to kill cancer cells by targeting mitochondria. Protecting mitochondria might be a potential therapeutic strategy for CDDP-induced side effects. ß-Lapachone (ß-lap), a recognized NAD+ booster, has been reported to regulate mitochondrial activity. However, it remains unclear whether maintaining mitochondrial activity is the key factor in the protective effects of ß-lap in CDDP-treated normal cells. PURPOSE: In this study, the protective effects of ß-lap on mitochondria against CDDP cytotoxicity in normal cells were evaluated. STUDY DESIGN: In vitro cell models were used in this study, including 3T3 fibroblasts, human dermal fibroblasts, MCF-7 breast cancer cells, and MDA-MB-231 breast cancer cells. METHODS: Cells were treated with CDDP and ß-lap, and cell survival, NAD+, mitochondrial activity, autophagy, and ATP production were measured. Various inhibitors and siRNAs were used to confirm the key signal underlying the protective effects of ß-lap. RESULTS: The results demonstrated that ß-lap significantly decreased CDDP cytotoxicity in normal fibroblasts. With various inhibitors and siRNAs, ß-lap reduced CDDP-induced damage to normal fibroblasts by maintaining mitochondrial activity and increasing autophagy through the NQO1/NAD+/SIRT1 axis. Most importantly, the protective effects of ß-lap in fibroblasts did not affect the therapeutic effects of CDDP in cancer cells. This study indicated that mitochondrial activity, energy production, and NQO1 levels might be crucial responses separating normal cells from cancer cells under exposure to CDDP and ß-lap. CONCLUSION: ß-lap could be a good synergistic drug for reducing the side effects of CDDP without affecting the anticancer drug effect.

BSA-bounded p-cresyl sulfate potentiates the malignancy of bladder carcinoma by triggering cell migration and EMT through the ROS/Src/FAK signaling pathway.

Para-cresyl sulfate (P-CS), a major uremic toxin derived from the metabolites of tyrosine and phenylalanine through liver, existed in the blood of patients with chronic kidney disease (CKD). CKD increases the malignancy in bladder cancers; however, effects of P-CS on bladder cancers are not fully understood. P-CS is conjugated with BSA physiologically, and this study aims to investigate the effects and possible underlying mechanisms of BSA-bounded P-CS on human bladder cancer cells. With P-CS treatment, the intracellular ROS increased in bladder cancer cells. ROS then triggered epithelial-mesenchymal transition (EMT), stress fiber redistribution, and cell migration. With specific inhibitors, the key signals regulating P-CS-treated migration are Src and FAK. This study provided a clinical clue that patients with higher serum P-CS have a higher risk of malignant urothelial carcinomas, and a regulatory pathway of how P-CS regulates bladder cancer migration.

Nrf2 is the key to chemotherapy resistance in MCF7 breast cancer cells under hypoxia.

Hypoxia leads to reactive oxygen species (ROS) imbalance, which is proposed to associate with drug resistance and oncogenesis. Inhibition of enzymes of antioxidant balancing system in tumor cells was shown to reduce chemoresistance under hypoxia. However, the underlying mechanism remains unknown. The key regulator of antioxidant balancing system is nuclear factor erythroid 2-related factor 2 (NFE2L2, Nrf2). In this study, we showed that hypoxia induced ROS production and increased the Nrf2 activity. Nrf2 activation increased levels of its downstream target antioxidant enzymes, including GCLC and GCLM. The Nrf2-overexpressing also confers chemo-resistant MCF7 cells under normoxia. The in vivo mouse model also demonstrated that the chemical inhibition of Nrf2 can increase cisplatin (CDDP) cytotoxicity. Together, these results showed that Nrf2 serves as a key regulator in chemotherapeutic resistance under hypoxia through ROS-Nrf2-GCLC-GSH pathway. Therefore, targeting Nrf2 can be a potential treatment for hypoxia-induced drug resistance in breast cancer cells.

BC3EE2,9B, a synthetic carbazole derivative, upregulates autophagy and synergistically sensitizes human GBM8901 glioblastoma cells to temozolomide.

Glioblastoma multiforme (GBM) is the most fatal form of human brain cancer. Although temozolomide (TMZ), an oral alkylating chemotherapeutic agent, improves the survival rate, the prognosis of patients with GBM remains poor. Naturally occurring carbazole alkaloids isolated from curry leaves (Murraya koenigii Spreng.) have been shown to possess a wide range of anticancer properties. However, the effects of carbazole derivatives on glioblastoma cells remain poorly understood. In the present study, anti­glioblastoma profiles of a series of synthetic carbazole derivatives were evaluated in vitro. The most promising derivative in this series was BC3EE2,9B, which showed significant anti­proliferative effects in GBM8401 and GBM8901 cells. BC3EE2,9B also triggered cell­cycle arrest, most prominently at the G1 stage, and suppressed glioblastoma cell invasion and migration. Furthermore, BC3EE2,9B induced autophagy­mediated cell death and synergistically sensitized GBM cells to TMZ cytotoxicity. The possible mechanism underlying BC3EE2,9B­induced autophagy may involve activation of adenosine monophosphate-activated protein kinase and the attenuation of the Akt and mammalian target of the rapamycin downstream signaling pathway. Taken together, the present results provide molecular evidence for the mode of action governing the ability of BC3EE2,9B to sensitize drug­resistant glioblastoma cells to the chemotherapeutic agent TMZ.

Andrographolide induces apoptosis of C6 glioma cells via the ERK-p53-caspase 7-PARP pathway.

BACKGROUND: Glioma is the most malignant tumor of the central nervous system. Efforts on the development of new chemotherapy are mandatory. Andrographolide (AND), a diterpenoid lactone isolated from the Andrographis paniculata, has been shown to have antitumor activities in several types of cancer cells. Whether AND can exert its antitumor activity in glioblastoma cells remains unknown. This study examined the anticancer effects of AND, both in vitro and in vivo. METHODS: Cell apoptosis was assayed by flow cytometry and nuclear staining. The signaling pathway for AND was determined by western blotting. The effects of AND on tumor growth was evaluated in a mouse model. RESULTS AND CONCLUSION: In vitro, with application of specific inhibitors and siRNA, AND-induced apoptosis was proven through ROS-ERK-P53-caspase 7-PARP signaling pathway. In vivo, AND significantly retarded tumor growth and caused regression of well-formed tumors in vivo. Furthermore, AND did not induce apoptosis or activate ERK and p53 in primary cultured astrocyte cells, and it may serve as a potential therapeutic candidate for the treatment of glioma.

Cordycepin induces apoptosis of C6 glioma cells through the adenosine 2A receptor-p53-caspase-7-PARP pathway.

Cordycepin, 3'-deoxyadenosine from Cordyceps sinensis, has been shown to exert anti-tumor effects in several cancer cell lines. This study investigated the effect of cordycepin on a rat glioma cell line. Cordycepin caused apoptosis in C6 glioma cells in a time- and concentration-dependent manner, but did not affect the survival of primary cultured rat astrocytes. Cordycepin increased the total protein levels of p53 and phosphorylated p53 in the C6 cells. Levels of cleaved caspase-7 and poly (ADP-ribose) polymerase (PARP), but not cleaved caspase-3, were also increased after cordycepin treatment. Specific inhibitors for p53 and caspases abrogated cordycepin-induced caspase-7 and PARP cleavage, and prevented cordycepin-induced apoptosis. Moreover, siRNA knockdown of p53 blocked cordycepin-induced cleavage of caspase-7 and PARP. Both adenosine 2A receptor (A2AR) antagonist and small interference RNA (siRNA) knockdown of A2AR blocked cordycepin-induced apoptosis, p53 activation, and caspase-7 and PARP cleavage. These may provide a new strategy of cordycepin for glioma therapy in the future.

Daidzein induces neuritogenesis in DRG neuronal cultures.

BACKGROUND: Daidzein, a phytoestrogen found in isoflavone, is known to exert neurotrophic and neuroprotective effects on the nervous system. Using primary rat dorsal root ganglion (DRG) neuronal cultures, we have examined the potential neurite outgrowth effect of daidzein. METHODS: Dissociated dorsal root ganglia (DRG) cultures were used to study the signaling mechanism of daidzein-induced neuritogenesis by immunocytochemistry and Western blotting. RESULTS: In response to daidzein treatment, DRG neurons showed a significant increase in total neurite length and in tip number per neuron. The neuritogenic effect of daidzein was significantly hampered by specific blockers for Src, protein kinase C delta (PKCδ) and mitogen-activated protein kinase/extracellular signal-regulated kinase kinases (MEK/ERK), but not by those for estrogen receptor (ER). Moreover, daidzein induced phosphorylation of Src, PKCδ and ERK. The activation of PKCδ by daidzein was attenuated in the presence of a Src kinase inhibitor, and that of ERK by daidzein was diminished in the presence of either a Src or PKCδ inhibitor. CONCLUSION: Daidzein may stimulate neurite outgrowth of DRG neurons depending on Src kinase, PKCδ and ERK signaling pathway.

Uremic toxin p-cresol induces disassembly of gap junctions of cardiomyocytes.

High serum levels of p-cresol have been associated with cardiovascular diseases. This study investigated the effects of p-cresol on gap junctions in neonatal cultured cardiomyocytes. p-Cresol reduced the spontaneous contraction rates of cardiomyocytes, and caused irregular cardiomyocyte beating. Junctional connexin 43 (Cx43) plaques became smaller in size and the gap junction intercellular communication (GJIC) impaired. Moreover, p-cresol increased intracellular Ca(+2) levels, and induced Ca(+2)-dependent protein kinase Cα (PKCα) activation. p-Cresol decreased P1 and P2 Cx43 levels, and increased non-phosphorylated S368-Cx43 levels. The above changes as well as Cx43 disassembly and GJIC decrease induced by p-cresol were prevented by the BAPTA-AM or PKCα inhibitor Gö6976. These results suggest that PKCα mediates p-cresol-induced gap junction disassembly and GJIC dysfunction via S368-Cx43 serine dephosphorylation. This hypothesis was further confirmed in H9c2 cells by siRNA approach. SiRNA knockdown of PKCα prevented p-cresol-induced increase in nonphosphorylated Cx43. This finding supports the association of p-cresol and cardiovascular diseases.