Ultraviolet (UV) radiation and reactive oxygen species (ROS) impair the physiological functions of retinal pigment epithelium (RPE) cells by inducing cell apoptosis, which is the main cause of age-related macular degeneration (AMD). The mechanism by which UV/ROS induces RPE cell death is not fully addressed. Here, we observed the activation of a ceramide-endoplasmic reticulum (ER) stress-AMP activated protein kinase (AMPK) signaling axis in UV and hydrogen peroxide (H2O2)-treated RPE cells. UV and H2O2 induced an early ceramide production, profound ER stress and AMPK activation. Pharmacological inhibitors against ER stress (salubrinal), ceramide production (fumonisin B1) and AMPK activation (compound C) suppressed UV- and H2O2-induced RPE cell apoptosis. Conversely, cell permeable short-chain C6 ceramide and AMPK activator AICAR (5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide) mimicked UV and H2O2’s effects and promoted RPE cell apoptosis. Together, these results suggest that UV/H2O2 activates the ceramide-ER stress-AMPK signaling axis to promote RPE cell apoptosis.

Inhibitors of DNA methyltransferases (DNMTis) or histone deacetylases (HDACis) are epigenetic drugs which are investigated since decades. Several have been approved and are applied in the treatment of hematopoietic and lymphatic malignancies, although their mode of action has not been fully understood. Two recent findings improved mechanistic insights: i) activation of human endogenous retroviral elements (HERVs) with concomitant synthesis of double-stranded RNAs (dsRNAs), and ii) massive activation of promoters from long terminal repeats (LTRs) which originated from past HERV invasions. These dsRNAs activate an antiviral response pathway followed by apoptosis. LTR promoter activation leads to synthesis of non-annotated transcripts potentially encoding novel or cryptic proteins. Here, we discuss the current knowledge of the molecular effects exerted by epigenetic drugs with a focus on DNMTis and HDACis. We highlight the role in LTR activation and provide novel data from both in vitro and in vivo epigenetic drug treatment.

Inflammasome activation can trigger an inflammatory and innate immune response through the release of cytokines and induction of pyroptosis. A dysfunctional inflammasome has been implicated in the development of human pathologies, including sepsis and septic shock. Here, we show that advanced glycosylation end-product specific receptor (AGER/RAGE) is required for caspase-11 inflammasome activation in macrophages. A nuclear damage-associated molecular pattern (nDAMP) complex, including high-mobility group box 1, histone, and DNA, can promote caspase-11-mediated gasdermin D cleavage, interleukin 1β proteolytic maturation, and lactate dehydrogenase release. The inhibition of AGER-mediated lipid peroxidation via arachidonate 5-lipoxygenase (ALOX5) limits caspase-11 inflammasome activation and pyroptosis in macrophages in response to nDAMPs or cytosolic lipopolysaccharide. Importantly, the pharmacologic inhibition of the AGER-ALOX5 pathway or global depletion ( Ager −/− ) or conditional depletion of AGER in myeloid cells ( Ager Mye −/− ) protects against lipopolysaccharide-induced septic death in poly(I:C)-primed mice. These data identify a molecular basis for caspase-11 inflammasome activation and provide a potential strategy to treat sepsis.

Edema formation has been linked to thrombin toxicity induced by blood clot at the acute stage of intracerebral hemorrhage. Thrombin induces cell toxicity in neuron, microglia and astrocyte. Aquaporin (AQP) 4 and 9 are proteins expressed on astrocyte in rat brain and involved in the brain water accumulation in brain edema. Recombinant hirudin (r-Hirudin) is a direct inhibitor of thrombin that can block the toxicitic effect of thrombin. In this study, we demonstrated that autologous whole blood infusion in caudate nucleus up-regulates the expression of AQP4 and AQP9 mRNAs and proteins. AQP4 and AQP9 mRNAs expression peaked at about 6 h after blood infusion. The AQP4 protein peaked at about 48 h while AQP9 at about 24 h after blood infusion. Thrombin induced up-regulation of AQP4 and AQP9 were inhibited by r-Hirudin administration and significantly decreased the expression of both AQPs. We further investigated the relationship between edema formation and expression of AQP4 and AQP9. The data presented here may be helpful in optimizing r-Hirudin as an anti-thrombin drug in the treatment of edema at the acute stage of ICH.

Because conventional chemotherapy is not sufficiently effective against prostate cancer, various examinations have been performed to identify anticancer activity of naturally occurring components and their mechanisms of action. The (+)-brevipolide H, an α-pyrone-based natural compound, induced potent and long-term anticancer effects in human castration-resistant prostate cancer (CRPC) PC-3 cells. Flow cytofluorometric analysis with propidium iodide staining showed (+)-brevipolide H-induced G1 arrest of cell cycle and subsequent apoptosis through induction of caspase cascades. Since Akt/mTOR pathway has been well substantiated in participating in cell cycle progression in G1 phase, its signaling and downstream regulators were examined. Consequently, (+)-brevipolide H inhibited the signaling pathway of Akt/mTOR/p70S6K. The c-Myc inhibition and downregulation of G1 phase cyclins were also attributed to (+)-brevipolide H action. Overexpression of myristoylated Akt significantly rescued mTOR/p70S6K and downstream signaling under (+)-brevipolide H treatment. ROS and Ca2+, two key mediators in regulating intracellular signaling, were determined, showing that (+)-brevipolide H interactively induced ROS production and an increase of intracellular Ca2+ levels. The (+)-Brevipolide H also induced the downregulation of anti-apoptotic Bcl-2 family proteins (Bcl-2 and Bcl-xL) and loss of mitochondrial membrane potential, indicating the contribution of mitochondrial dysfunction to apoptosis. In conclusion, the data suggest that (+)-brevipolide H displays anticancer activity through crosstalk between ROS production and intracellular Ca2+ mobilization. In addition, suppression of Akt/mTOR/p70S6K pathway associated with downregulation of G1 phase cyclins contributes to (+)-brevipolide H-mediated anticancer activity, which ultimately causes mitochondrial dysfunction and cell apoptosis. The data also support the biological significance and, possibly, clinically important development of natural product-based anticancer approaches.