Involvement of the mitochondrion-dependent pathway and oxidative stress in the apoptosis of murine splenocytes induced by areca nut extract

PPARγ regulates osteoarthritis chondrocytes apoptosis through caspase-3 dependent mitochondrial pathway

Osteoarthritis (OA) is the most prevalent form of arthritis, characterized by a complex pathogenesis. One of the key factors contributing to its development is the apoptosis of chondrocytes triggered by oxidative stress. Involvement of peroxisome proliferator-activated receptor gamma (PPARγ) has been reported in the regulation of oxidative stress. However, there remains unclear mechanisms that through which PPARγ influences the pathogenesis of OA. The present study aims to delve into the role of PPARγ in chondrocytes apoptosis induced by oxidative stress in the context of OA. Primary human chondrocytes, both relatively normal and OA, were isolated and cultured for the following study. Various assessments were performed, including measurements of cell proliferation, viability and cytotoxicity. Additionally, we examined cell apoptosis, levels of reactive oxygen species (ROS), nitric oxide (NO), mitochondrial membrane potential (MMP) and cytochrome C release. We also evaluated the expression of related genes and proteins, such as collagen type II (Col2a1), aggrecan, inducible nitric oxide synthase (iNOS), caspase-9, caspase-3 and PPARγ. Compared with relatively normal cartilage, the expression of PPARγ in OA cartilage was down-regulated. The proliferation of OA chondrocytes decreased, accompanied by an increase in the apoptosis rate. Down-regulation of PPARγ expression in OA chondrocytes coincided with an up-regulation of iNOS expression, leading to increased secretion of NO, endogenous ROS production, and decrease of MMP levels. Furthermore, we observed the release of cytochrome C, elevated caspase-9 and caspase-3 activities, and reduction of the components of extracellular matrix (ECM) Col2a1 and aggrecan. Accordingly, utilization of GW1929 (PPARγ Agonists) or Z-DEVD-FMK (caspase-3 inhibitor) can protect chondrocytes from mitochondrial-related apoptosis and alleviate the progression of OA. During the progression of OA, excessive oxidative stress in chondrocytes leads to apoptosis and ECM degradation. Activation of PPARγ can postpone OA by down-regulating caspase-3-dependent mitochondrial apoptosis pathway.

Endomorphin-2 Analog Inhibits the Growth of DLD-1 and RKO Human Colon Cancer Cells by Inducing Cell Apoptosis

Background

In developed countries, colon cancer is a leading cause of cancer-associated mortality. Dietary changes have resulted in an increased incidence of colon cancer in Asia. This study aimed to investigate the effects of the structural analog of endomorphin-2 (H-Tyr-Pro-Phe-Phe-NH₂) on human colon cancer cells in vitro.

Material/Methods

Human DLD-1 and RKO colon cancer cells and CCD-18Co normal human colonic fibroblasts were treated with increasing doses of the structural analog of endomorphin-2. Cells underwent the MTT assay, fluorescence confocal flow cytometry, and Hoechst 33258 staining to investigate cell proliferation, the cell cycle, and apoptosis. Western blot was used to measure the expression levels of poly(ADP-ribose) polymerase-1 (PARP-1), cytochrome c, caspase-3, and caspase-9. The 2′,7′-dichlorofluorescein diacetate (DCFH-DA) fluorescence method measured reactive oxygen species (ROS).

Results

Cell proliferation of DLD-1 and RKO cells was inhibited by the endomorphin-2 analog in a dose-dependent manner, and a 100 μM dose reduced DLD-1 and RKO cell proliferation by 28% and 23%, respectively, at 72 h. Endomorphin-2 analog induced cell apoptosis and the generation of ROS, activated caspase-3 and caspase-9, and increased the levels of p53 and cytochrome c release, and down-regulated of Akt activation in DLD-1 and RKO cells in a dose-dependent manner. Treatment of the DLD-1 and RKO cells with the endomorphin-2 analog increased the expression of Bax and reduced the expression of Bcl-2.

Conclusions

Endomorphin-2 analog inhibited colon cancer cell proliferation, activated apoptosis, and down-regulated Akt phosphorylation of human DLD-1 and RKO colon cancer cells in vitro in a dose-dependent manner.

Inhibition of Colon Cancer Cell Growth by Imidazole Through Activation of Apoptotic Pathway

Background

This study aimed to investigate the inhibitory effect of imidazole on colon cancer cell proliferation and understand the mechanism involved.

Material/Methods

MTT assay and flow cytometry using Hoechst 33258 staining were used to assess cell proliferation and morphology, respectively. Changes in protein expression was determined by western blotting assay. The reactive oxygen species (ROS) production in DLD-1 cells was analyzed by flow cytometry using DCFH-DA (2′,7′-dichlorofluorescein diacetate) stain.

Results

DLD-1 and HCT-116 cell viability was suppressed by imidazole in a concentration-based manner. At the concentration of 36 μM, imidazole reduced DLD-1 and HCT-116 cell viability to 22% and 28%, respectively. Treatment with imidazole led to chromatin material condensation, detaching of cells, and apoptotic nuclei. In imidazole treated cells, the G1/G0 phase cell proportion increased, whereas in the S and G2/M phases the cell proportion decreased. Imidazole treatment of DLD-1 cells markedly promoted activation of caspase-3, caspase-8, and caspase-9. The level of cleaved PARP1 was also upregulated in DLD-1 cells with imidazole treatment. Treatment of DLD-1 cells with imidazole suppressed Bcl-2 and promoted Bax, p53, and cytc expression. The Akt activation was suppressed by imidazole treatment in DLD-1 cells. ROS generation in DLD-1 cells was enhanced markedly by treatment with imidazole.

Conclusions

The present study demonstrated that imidazole inhibited colon cancer cell viability through activation of apoptosis and cell cycle arrest by increasing the generation of ROS, caspase activation, and apoptotic protein expression. Therefore, imidazole can act as a therapeutic molecule for the treatment of colon cancer.

Isoflavone lupiwighteone induces cytotoxic, apoptotic, and antiangiogenic activities in DU-145 prostate cancer cells

Isoflavones constitute a large series of compounds found in many plants. They make up an important part of the diet and have a broad spectrum of biological activities such as cytotoxic and antitumor effects. Lupiwighteone (Lup) is an isoflavone-type compound. It is distributed widely in wild-growing plants such as Glycyrrhiza glabra, Lupinus, and Lotus pedunculatus. On the basis of existing research, Lup shows antioxidant and antimicrobial effects, but its antitumor activity has not been reported as yet. This study aimed to examine the antitumor activity of Lup, explore its antitumor mechanism in a human prostate carcinoma cell line (DU-145), and evaluate its antiangiogenetic activity in the human umbilical vein endothelial cell line (HUVEC). The results showed that Lup could inhibit the growth of DU-145 and HUVEC cells in a concentration-dependent and time-dependent manner by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Flow cytometry analysis indicated that Lup could induce cell cycle arrest, cells apoptosis, mitochondrial membrane potential loss, and an increase in intracellular reactive oxygen species of DU-145 cells. Upregulation of Bax, cytochrome c, caspase-3, and PARP-1 protein expressions and downregulation of Bcl-2, procaspase-9, and p-Akt protein expressions were observed by western blot after the treatment of Lup. Furthermore, the effects of Lup on the cellular behavior of HUVECs were also investigated. Altogether, our data proved the anticancer and antiangiogenesis potential of Lup.

Inhibitory effects of 3-bromopyruvate in human nasopharyngeal carcinoma cells

Tumor cells depend on aerobic glycolysis for adenosine triphosphate (ATP) production, which is therefore targeted by therapeutic agents. The compound 3-bromopyruvate (3-BrPA), a strong alkylating agent and hexokinase inhibitor, inhibits tumor cell glycolysis and the production of ATP, causing apoptosis. 3-BrPA induces apoptosis of nasopharyngeal carcinoma (NPC) cell lines HNE1 and CNE-2Z, which may be related to its molecular mechanisms. In the present study, we investigated the effects of 3-BrPA on the viability, reactive oxygen species (ROS), apoptosis and other types of programmed cell death in NPC cells in vitro and in vivo. PI staining showed significant apoptosis in NPC cells accompanied by the overproduction of ROS and downregulation of mitochondrial membrane potential (MMP, ΔΨm) by 3-BrPA. However, the ROS scavenger N-acetyl-L-cysteine (NAC) significantly reduced 3-BrPA-induced apoptosis by decreasing ROS and facilitating the recovery of MMP. We elucidated the molecular mechanisms underlying 3-BrPA activity and found that it caused mitochondrial dysfunction and ROS production, leading to necroptosis of NPC cells. We investigated the effects of the caspase inhibitor z-VAD-fmk, which inhibits apoptosis but promotes death domain receptor (DR)-induced NPC cell necrosis. Necrostatin-1 (Nec-1) inhibits necroptosis, apparently via a DR signaling pathway and thus abrogates the effects of z-VAD‑fmk. In addition, we demonstrated the effective attenuation of 3-BrPA-induced necrotic cell death by Nec-1. Finally, animal studies proved that 3-BrPA exhibited significant antitumor activity in nude mice. The present study is the first demonstration of 3-BrPA-induced non-apoptotic necroptosis and ROS generation in NPC cells and provides potential strategies for developing agents against apoptosis‑resistant cancers.

Areca nut extracts enhance the development of CD11b(+) Gr-1(+) cells with the characteristics of myeloid-derived suppressor cells in antigen-stimulated mice

BACKGROUND

Areca quid chewing is an etiological factor contributing to the development of oral cancer and pre-cancers, whose pathophysiology has been linked to inflammation and immune deterioration. Myeloid-derived suppressor cells (MDSC) play a key role in the regulation of immunity under certain pathological conditions, such as inflammation and cancer. As areca nut extracts (ANE) have been reported to induce a proinflammatory effect in antigen-stimulated mice, we hypothesized that ANE might enhance the development of MDSC.

METHODS

Ovalbumin (OVA)-sensitized BALB/c mice were daily administered with ANE (5-50 mg/kg), polyphenol-enriched ANE (PANE; 25 mg/kg) or arecoline (5 mg/kg) by intraperitoneal injection for 10 doses. The mouse footpads were then subcutaneously challenged with OVA to induce local inflammatory responses.

RESULTS

ANE and PANE treatment significantly increased the spleen index and the population of CD11b(+) Gr-1(+) cells in the spleen and peripheral blood, whereas arecoline was inactive. In addition, ANE and PANE treatment enhanced the expression of cytokines and enzymes associated with the immunosuppressive function of MDSC, including IL-10, arginase-I and iNOS in splenic CD11b(+) cells. Concordantly, ANE and PANE treatment augmented the infiltration of Gr-1(+) IL-10(+) cells in the footpads challenged with OVA.

CONCLUSIONS

Our results suggested that areca nut constituents, in particular, polyphenols enhanced the development of myeloid-derived suppressor cells in vivo, which may be a critical mechanism linking inflammation and the compromised immunity reported to be associated with the pathophysiology of areca-related oral diseases.

The involvement of ROS overproduction and mitochondrial dysfunction in PBDE-47-induced apoptosis on Jurkat cells

2,2',4,4'-Tetrabromodiphenyl ether (PBDE-47), as one of the congeners of polybrominated diphenyl ethers (PBDEs), is widely present and threatens the human health in many aspects. This study aims to investigate the toxic effects of PBDE-47 on cell viability, apoptosis, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) of Jurkat cells in vitro. The results showed that PBDE-47 significantly inhibited the viability of Jurkat cells in a dose-dependent manner by alamar blue assay. Significant induction of apoptosis was detected in Jurkat cells at 25-100 μM by propidium iodide staining, accompanied with overproduction of ROS and downregulation of MMP. Furthermore, N-acetyl-L-cysteine (NAC), a widely used ROS scavenger, significantly reduced the PBDE-47-induced apoptosis by decreasing ROS level and mediating recovery of the MMP. In conclusion, the results of this study suggest that PBDE-47 could induce apoptosis in Jurkat cells and ROS and mitochondrial dysfunction play important roles in the apoptotic process.