Hydrogen peroxide induces apoptotic-like cell death in coelomocytes of Themiste petricola (Sipuncula)

The Role of Pseudo-Orthocaspase (SyOC) of Synechocystis sp. PCC 6803 in Attenuating the Effect of Oxidative Stress

Caspases are proteases, best known for their involvement in the execution of apoptosis-a subtype of programmed cell death, which occurs only in animals. These proteases are composed of two structural building blocks: a proteolytically active p20 domain and a regulatory p10 domain. Although structural homologs appear in representatives of all other organisms, their functional homology, i.e., cell death depending on their proteolytical activity, is still much disputed. Additionally, pseudo-caspases and pseudo-metacaspases, in which the catalytic histidine-cysteine dyad is substituted with non-proteolytic amino acid residues, were shown to be involved in cell death programs. Here, we present the involvement of a pseudo-orthocaspase (SyOC), a prokaryotic caspase-homolog lacking the p10 domain, in oxidative stress in the model cyanobacterium Synechocystis sp. PCC 6803. To study the in vivo impact of this pseudo-protease during oxidative stress its gene expression during exposure to H₂O₂ was monitored by RT-qPCR. Furthermore, a knock-out mutant lacking the pseudo-orthocaspase gene was designed, and its survival and growth rates were compared to wild type cells as well as its proteome. Deletion of SyOC led to cells with a higher tolerance toward oxidative stress, suggesting that this protein may be involved in a pro-death pathway.

Effects of Cadmium and Zinc on the Gamete Viability, Fertilization, and Embryonic Development of Tripneustes gratilla (Linnaeus)

Heavy metals are frequently reported for their mutagenic and teratogenic effects on benthic organisms. Thus, this study aimed to determine the toxicity of cadmium (Cd) and zinc (Zn) in the gametes of T. gratilla and to compare its fertilization and embryonic development under the highest nongametotoxic concentrations of these heavy metals. Gamete viability of T. gratilla under CdCl2 and ZnSO4 treatments was assayed through resazurin reduction test (RRT) and was confirmed through gamete morphology assay. ZnSO4 was more toxic to T. gratilla gametes than CdCl2 and egg cells were more sensitive to both than the sperm cells. Higher concentrations of CdCl2 and ZnSO4 induced gamete apoptosis and necrosis while highest nongametotoxic concentrations were determined at 1 × 10(-3) M and 1 × 10(-4) M, respectively, and were used in an in vitro fertilization and embryonic development experiment. ZnSO4 treatment inhibited fertilization more than CdCl2 and yielded more deformed embryos, while both induced abnormalities and hindered further embryonic development. This study gives the first report on the specific concentrations of Cd and Zn that are toxic to T. gratilla gametes and has confirmed the teratogenic effects of these heavy metals.

Cordycepin, a Natural Antineoplastic Agent, Induces Apoptosis of Breast Cancer Cells via Caspase-dependent Pathways

Cordycepin, a major compound separated from Cordyceps sinensis, is known as a potential novel candidate for cancer therapy. Breast cancer, the most typical cancer diagnosed among women, remains a global health problem. In this study, the anti-breast cancer property of cordycepin and its underlying mechanisms was investigated. The direct effects of cordycepin on breast cancer cells both in in vitro and in vivo experiments were evaluated. Cordycepin exerted cytotoxicity in MCF-7 and MDA-MB-231 cells confirmed by reduced cell viability, inhibition of cell proliferation, enhanced lactate dehydrogenase release and reactive oxygen species accumulation, induced mitochondrial dysfunction and nuclear apoptosis in human breast cancer cells. Cordycepin increased the activation of pro-apoptotic proteins, including caspase-8, caspase-9, caspase-3 and Bax, and suppressed the expression of the anti-apoptotic protein, B-cell lymphoma 2 (Bcl-2). The inhibition on MCF-7-xenografted tumor growth in nude mice further confirmed cordycepin's anti-breast cancer effect. These aforementioned results reveal that cordycepin induces apoptosis in human breast cancer cells via caspase-dependent pathways. The data shed light on the possibility of cordycepin being a safe agent for breast cancer treatment.

Apoptotic and necrotic changes in the midgut glands of the wolf spider Xerolycosa nemoralis (Lycosidae) in response to starvation and dimethoate exposure

In the present study, the intensity of degenerative changes (apoptosis, necrosis) in the cells of the midgut glands of male and female wolf spiders, Xerolycosa nemoralis (Lycosidae), exposed to natural (starvation) and anthropogenic (the organophosphorous pesticide dimethoate) stressors under laboratory conditions were compared. The spiders were collected from two differentially polluted sites, both located in southern Poland: Katowice-Welnowiec, which is heavily polluted with metals, and Pilica, the reference site. Starvation and dimethoate treatment resulted in enhancement of apoptotic and necrotic changes in the midgut glands of the spiders. The frequency of degenerative changes in starving individuals was twice as high as in the specimens intoxicated with dimethoate. The percentage of apoptotic and necrotic cells was higher in starving males than in starving females. A high intensity of necrotic changes, together with increased Cas-3 like activity and a greater percentage of cells with depolarized mitochondria, were typical of starving males from the polluted site. The cell death indices observed in females depended more strongly on the type of stressor than on previous preexposure to pollutants.

Chelerythrine induces reactive oxygen species-dependent mitochondrial apoptotic pathway in a murine T cell lymphoma

Chelerythrine is a well-known protein kinase C inhibitor and potential antiproliferative and antitumor pharmacological agent. Chelerythrine inhibits/suppresses the HSF1 phosphorylation by inhibiting PKC and blocks the nuclear migration and subsequent synthesis of hsp70 leading to reduced cell viability and activation of apoptotic machinery. Chelerythrine is also known to enhance the production of reactive oxygen intermediate that is strong activator of apoptosis in high concentration. Therefore, the present study intended to investigate the role of chelerythrine-induced reactive oxygen intermediate on the viability and apoptosis of Dalton's lymphoma cells. Enhanced production of reactive oxygen species in Dalton's lymphoma (DL) cells was observed upon treatment of chelerythrine only which was seen completely abolished on treatment of mitochondrial complex inhibitors rotenone and malonate, and anti-oxidant, N-acetyl-L-cysteine. Increased number of DL cells undergoing apoptosis, as observed by fluorescent microscopy and flow cytometry analysis, in chelerythrine only-treated group was seen that was significantly inhibited on treatment of mitochondrial complex inhibitors and anti-oxidants. Staurosporine, on the other hand, does not lead to enhanced production of reactive oxygen intermediate in DL cells.

Pathogen-associated molecular pattern-induced mitochondrial membrane depolarization in the earthworm Eisenia hortensis

Innate immune responses of the earthworm Eisenia hortensis were studied by detecting mitochondrial membrane depolarization and reactive oxygen species (ROS) production after incubation with pathogen-associated molecular patterns (PAMPs). Coelomocytes from E. hortensis were incubated with zymosan, flagellin, or peptidoglycan (PTG) for 48 h in vitro and studied using flow cytometric assays for changes in mitochondrial membrane potential (ΔΨ(m)) or ROS production using the fluorescent indicators JC-1 or DHR 123, respectively. All three PAMPs evoked ΔΨ(m), with zymosan inducing the most significant membrane depolarization in coelomocyte samples compared to untreated controls. When treated with zymosan or flagellin, coelomocyte samples exhibited significant increases in ROS production in the zymosan sample after 16 h of in vitro incubation, but this effect was not observed for flagellin. These results demonstrate that PAMPs evoke evolutionarily conserved cellular responses which may be important during innate immune defenses to eradicate intracellular reserves of foreign pathogens.

The antioxidants dimethylsulfoxide and dimethylthiourea affect the immediate adhesion responses of larval haemocytes from 3 lepidopteran insect species

Antioxidants, dimethylsulfoxide (DMSO) and dimethylthiourea (DMTU), at concentrations not affecting the viability of blood cells (haemocytes) from the larval stage of 3 lepidopteran insects - Galleria mellonella, Lymantria dispar, and Malacosoma disstria - differed in their influence on the innate binding of haemocytes to glass, bacteria to haemocytes, and on humoral responses to alien materials. In vitro DMSO had little effect, whereas DMTU substantially impaired the adhesion of the haemocyte types, the plasmatocytes and granular cells, to slides as well as the attachment of Bacillus subtilis to these haemocytes. Although both antioxidants increased lysozyme and phenoloxidase activities, there was no correlation of enzyme activity and haemocyte adhesion responses, possibly reflecting sequestered radicals. Nitric oxide and hydroxyl radicals offset the DMTU effect. In the absence of antioxidants, inactivate protein kinases A (PKA) and C (PKC) enhanced haemocyte aggregation. In general, DMSO, as opposed to DMTU, did not alter the effects of PKA and PKC activators and inhibitors on haemocyte aggregation or of PKC and PKA activities. High concentrations of DMSO and all levels of DMTU, although inhibiting PKA and PKC, inhibited haemocyte adhesion to slides. Comparable results occurred for DMTU-treated haemocytes incubated with B. subtilis. In vivo DMSO, unlike DMTU, did not impair plasmatocyte or granular cell responses to foreign materials, including bacterial removal from the haemolymph and nodulation.

Physiological characterization of stolon regression in a colonial hydroid

As with many colonial animals, hydractiniid hydroids display a range of morphological variation. Sheet-like forms exhibit feeding polyps close together with short connecting stolons, whereas runner-like forms have more distant polyps and longer connecting stolons. These morphological patterns are thought to derive from rates of stolon growth and polyp formation. Here,stolon regression is identified and characterized as a potential process underlying this variation. Typically, regression can be observed in a few stolons of a normally growing colony. For detailed studies, many stolons of a colony can be induced to regress by pharmacological manipulations of reactive oxygen species (e.g. hydrogen peroxide) or reactive nitrogen species (e.g. nitric oxide). The regression process begins with a cessation of gastrovascular flow to the distal part of the stolon. High levels of endogenous H2O2 and NO then accumulate in the regressing stolon. Remarkably, exogenous treatments with either H2O2 or an NO donor equivalently trigger endogenous formation of both H2O2 and NO. Cell death during regression is suggested by both morphological features, detected by transmission electron microscopy, and DNA fragmentation, detected by TUNEL. Stolon regression may occur when colonies detect environmental signals that favor continued growth in the same location rather than outward growth.