Ac-FLTD-CMK inhibits pyroptosis and exerts neuroprotective effect in a mice model of traumatic brain injury.

Pyroptosis has been reported to contribute to the traumatic brain injury (TBI) process. Ac-FLTD-CMK is a newly synthesized pyroptosis inhibitor. However, whether Ac-FLTD-CMK inhibits pyroptosis and plays a neuroprotective role after TBI is unknown. The present study aimed to determine the effects of Ac-FLTD-CMK on TBI in a mouse model. Male C57BL/6 mice were randomly divided into sham, TBI + vehicle, and TBI + Ac-FLTD-CMK groups. TBI was induced using a weight-drop apparatus. Intraventricular injection of Ac-FLTD-CMK was performed 30 min after TBI. Caspase-1, caspase-11, gasdermin-D (GSDMD), and caspase-3 expression in the peri-contusional cortex were assessed by western blotting. Interleukin-1ß (IL-1ß) and interleukin-18 (IL-18) expression in the peri-contusional cortex were measured using ELISA. Behavioral experiments, brain water content, Evans blue extravasation, lactate dehydrogenase (LDH) release, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining were also performed. The results showed that Ac-FLTD-CMK administration significantly downregulated caspase-1 p20, caspase-11 p20, GSDMD N-terminal, IL-1ß, and IL-18 expression; reduced LDH release; alleviated neuronal death; attenuated brain edema and blood-brain barrier damage; and improved neurobehavioral function. These findings indicate that Ac-FLTD-CMK treatment suppresses pyroptosis and protects mice against TBI.

Caspase-4: A Therapeutic Target for Peptic Ulcer Disease.

Peptic ulcers are caused by the interaction between bacterial and host factors. This study demonstrates enhanced expression of caspase-4 in peptic ulcer patient biopsies, indicating that pyroptosis and noncanonical inflammasome activity may be processes involved in peptic ulcer disease. We show that primary murine macrophages infected with Helicobacter pylori upregulate caspase-11 (the ortholog of human caspase-4), activate caspase-1, and secrete IL-1ß. We demonstrate that misoprostol (a stable PGE1 analogue) decreased IL-1ß secretion and delayed lethality in vivo in a murine peritonitis model. PGE2 was shown to inhibit caspase-11-driven pyroptosis and IL-1ß secretion in macrophages. Overall, we provide evidence for a pathological role of caspase-4/11 in peptic ulcer disease and propose that targeting caspase-4 or inhibiting pyroptosis may have therapeutic potential in the management of peptic ulcers.

Saturated fatty acids activate caspase-4/5 in human monocytes, triggering IL-1ß and IL-18 release.

Obesity is associated with metabolic tissue infiltration by monocyte-derived macrophages. Saturated fatty acids contribute to proinflammatory gene induction in tissue-embedded immune cells. However, it is unknown how circulating monocytes, the macrophage precursors, react to high-fat environments. In macrophages, saturated fatty acids activate inflammatory pathways and, notably, prime caspase-associated inflammasomes. Inflammasome-activated IL-1ß contributes to type 2 diabetes. We hypothesized that 1) human monocytes from obese patients show caspase activation, and 2) fatty acids trigger this response and consequent release of IL-1ß/IL-18. Human peripheral blood monocytes were sorted by flow cytometry, and caspase activity was measured with a FLICA dye-based assay. Blood monocytes from obese individuals exhibited elevated caspase activity. To explore the nature and consequence of this activity, human THP1 monocytes were exposed to saturated or unsaturated fatty acids. Caspase activity was revealed by isoform-specific cleavage and enzymatic activity; cytokine expression/release was measured by qPCR and ELISA. Palmitate, but not palmitoleate, increased caspase activity in parallel to the release of IL-1ß and IL-18. Palmitate induced eventual monocyte cell death with features of pyroptosis (an inflammation-linked cell death program involving caspase-4/5), scored through LDH release, vital dye influx, cell volume changes, and nuclear morphology. Notably, selective gene silencing or inhibition of caspase-4/5 reduced palmitate-induced release of IL-1ß and IL-18. In summary, monocytes from obese individuals present elevated caspase activity. Mechanistically, palmitate activates a pyroptotic program in monocytes through caspase-4/5, causing inflammatory cytokine release, additional to inflammasomes. These caspases represent potential, novel, therapeutic targets to taper obesity-associated inflammation.

Butyric acid induces apoptosis via oxidative stress in Jurkat T-cells.

Reactive oxygen species (ROS) are essential for the induction of T-cell apoptosis by butyric acid, an extracellular metabolite of periodontopathic bacteria. To determine the involvement of oxidative stress in apoptosis pathways, we investigated the contribution of ROS in mitochondrial signaling pathways, death-receptor-initiated signaling pathway, and endoplasmic reticulum stress in butyric-acid-induced T-cell apoptosis. N-acetyl-L-Cysteine (NAC) abrogated mitochondrial injury, cytochrome c, AIF, and Smac release, and Bcl-2 and Bcl-xL suppression and Bax and Bad activation induced by butyric acid. However, the decrease in cFLIP expression by butyric acid was not restored by treatment with NAC; increases in caspase-4 and -10 activities by butyric acid were completely abrogated by NAC. NAC also affected the elevation of GRP78 and CHOP/GADD153 expression by butyric acid. These results suggest that butyric acid is involved in mitochondrial-dysfunction- and endoplasmic reticulum stress-mediated apoptosis in human Jurkat T-cells via a ROS-dependent mechanism.

Up-regulation of the endoplasmic reticulum stress-response in periodontal disease.

BACKGROUND: Endoplasmic reticulum (ER) stress is the cell response by activation of the unfolded protein response (UPR) pathway in a variety of conditions such as infection and aging. The UPR may be associated with the pathogenesis of periodontal disease because of the induction of apoptosis and activation of nuclear factor-kappaB (NF-kappaB), a transcription factor for pro-inflammatory cytokines. However, the relationship between ER stress and periodontal disease is yet to be determined. METHODS: The expression of UPR-related molecules was analyzed by real-time polymerase chain reaction and immunohistochemistry, respectively and compared between gingivitis and periodontitis. The gene expressions were also analyzed for macrophages stimulated with lipopolysaccharides (LPS) from Escherichia coli (E. coli), and Porphyromonas gingivalis (P. gingivalis) or IFN-gamma. RESULTS: The expression levels of UPR-related genes and HSP60 were significantly higher in periodontitis compared with gingivitis lesions. However, LPS from P. gingivalis but not E. coli or IFN-gamma failed to up-regulate the gene expression in macrophage. CONCLUSIONS: An inflammatory response may have profound effect on the UPR response, particularly in periodontitis patients. Considering the histological nature of periodontitis and the link between UPR and inflammatory responses via NF-kappaB, ER stress in B cells could be another pathological mechanism underlying periodontal disease.

Distinct mechanism of cell death is responsible for tunicamycin-induced ER stress in SK-N-SH and SH-SY5Y cells.

In order to elucidate underlying mechanism of cell death pathways in neuronal cells in humans, we studied responsible pathways involved in the endoplasmic reticulum (ER) stress-induced cell death in neuroblastoma cells, SK-N-SH and its neuroblast-type subclone SH-SY5Y cells. A time-dependent induction of ER chaperons, glucose regulated protein (GRP)78 and GRP94, was observed after treatment with tunicamycin (TM), and cell death was also induced concomitantly in both cells. Although the pro-caspase-12-like protein was defined in both cells, a decrease in the protein was observed in only SH-SY5Y cells after exposure to TM. In contrast, pro-caspase-4 was detected in only SK-N-SH cells, and the cleaved-form was induced by the treatment with TM. A caspase-4 inhibitor, Z-LEVD-FMK attenuated TM-induced cell death in SK-N-SH cells. Calpain- and caspase-3-mediated proteolysis of alpha II-spectrin was also increased after the treatment with TM in both cells. A calpain inhibitor, calpeptin, repressed TM-induced cell death in only SK-N-SH cells. GADD153/C/EBP homologous protein (CHOP) was significantly induced after exposure to TM in only SH-SY5Y cells and RNA interference to GADD153/CHOP repressed TM-induced cell death. These results demonstrate that induction of GADD153/CHOP plays a pivotal role in mechanism of ER stress-induced cell death in SH-SY5Y cells, on the other hand, cleavage of pro-caspase-4 by activation of calpain play a crucial role in SK-N-SH cells. It is also suggested that the relevance of caspase-4 to ER stress is cell-specific even between human-origin cell lines.

Calcium and survivin are involved in the induction of apoptosis by dihydroartemisinin in human lung cancer SPC-A-1 cells.

Dihydroartemisinin (DHA), a semisynthetic derivative of artemisinin isolated from the traditional Chinese herb Artemisia annua, is an effective novel antimalarial drug. Recent studies suggest that it also has anticancer effects. The present study investigated the apoptosis activity of DHA in cultured human lung cancer cells by terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay and flow cytometry. Intracellular free calcium concentrations in the lung cancer cells were evaluated by laser scanning confocal microscopy using Fura-3/AM as probe. The observations also indicated that DHA downregulated the mRNA and protein expression level of survivin in the lung cancer cell line SPC-A-1 cells, whereas it did not affect those of caspase-4. These results demonstrated that DHA can induce apoptosis of lung cancer cell line SPC-A-1 cells and that calcium and survivin participated in the apoptotic signalling pathways.