Neutrophil extracellular trap cell death requires both autophagy and superoxide generation

Neutrophil extracellular traps (NETs) are extracellular chromatin structures that can trap and degrade microbes. They arise from neutrophils that have activated a cell death program called NET cell death, or NETosis. Activation of NETosis has been shown to involve NADPH oxidase activity, disintegration of the nuclear envelope and most granule membranes, decondensation of nuclear chromatin and formation of NETs. We report that in phorbol myristate acetate (PMA)-stimulated neutrophils, intracellular chromatin decondensation and NET formation follow autophagy and superoxide production, both of which are required to mediate PMA-induced NETosis and occur independently of each other. Neutrophils from patients with chronic granulomatous disease, which lack NADPH oxidase activity, still exhibit PMA-induced autophagy. Conversely, PMA-induced NADPH oxidase activity is not affected by pharmacological inhibition of autophagy. Interestingly, inhibition of either autophagy or NADPH oxidase prevents intracellular chromatin decondensation, which is essential for NETosis and NET formation, and results in cell death characterized by hallmarks of apoptosis. These results indicate that apoptosis might function as a backup program for NETosis when autophagy or NADPH oxidase activity is prevented.     

Functional Differences Among Benthic Macroinvertebrate Communities in Reference Streams of Same Order in a Given Biogeographic Area

Ecological theory (Southwood, 1977. Journal of Animal Ecology 46: 337–365, 1988. Oikos 52: 3–18; Townsend, 1989. Journal of the North American Benthological Society 8: 36–50; Townsend & Hildrew, 1994. Freshwater Biology 31: 265–275) considers that spatio-temporal variations in habitats act as evolutionary forces on organisms, selecting for traits that maximize fitness. As a consequence, communities developed under same environmental conditions should present the same combination of species bio-ecological characteristics. The objective was to verify, using data from the same biogeographical zone, (1) if there was a unique suite of bio-ecological profiles for reference macrobenthic communities of `comparable' rivers or (2) if the distribution of bio-ecological traits within reference communities was significantly influenced by geology. The variability of 22 bio-ecological traits in 12 different sites was tested to evaluate the potential influence of geological substrate on biological and ecological features of reference stream communities. Observed patterns suggested that communities displayed highly stable bio-ecological profiles among sites (within a given biogeographical zone) whatever the substrate was, even if communities on clayey substrate exhibited slightly different bio/ecological characteristics than on others geologies. Nevertheless, the functional structure of macrobenthic communities in reference sites was quite stable in this biogeographical area. This study was restricted to the selected stream types and its results may not directly be transferred to other biogeographical areas and stream types. However, the perspective of a unique functional reference for streams of the same order in a given biogeographical area, improve functional comparison between observed vs. reference communities. This could simplify and objectively define the ecological status of a given site.     

Regulation of peroxisome proliferator-activated receptor alpha by protein kinase C

Peroxisome proliferator-activated receptor alpha (PPARalpha) is a nuclear receptor activated by fatty acids, hypolipidemic drugs, and peroxisome proliferators (PPs). Like other nuclear receptors, PPARalpha is a phosphoprotein whose activity is affected by a variety of growth factor signaling cascades. In this study, the effects of protein kinase C (PKC) on PPARalpha activity were explored. In vivo phosphorylation studies in COS-1 cells transfected with murine PPARalpha showed that the level of phosphorylated PPARalpha is increased by treatment with the PP Wy-14,643 as well as the PKC activator phorbol myristol acetate (PMA). In addition, inhibitors of PKC decreased Wy-14,643-induced PPARalpha activity in a variety of reporter assays. Overexpressing PKCalpha, -beta, -delta, and -zeta affected both basal and Wy-14,643-induced PPARalpha activity. Four consensus PKC phosphorylation sites are contained within the DNA binding (C-domain) and hinge (D-domain) regions of rat PPARalpha (S110, T129, S142, and S179), and their contribution to receptor function was examined. Mutation of T129 or S179 to alanine prevented heterodimerization of PPARalpha with RXRalpha, lowered the level of phosphorylation by PKCalpha and PKCdelta in vitro, and lowered the level of phosphorylation of transfected PPARalpha in transfected cells. In addition, the T129A mutation prevented PPARalpha from binding DNA in an electromobility shift assay. Together, these studies demonstrate a direct role for PKC in the regulation of PPARalpha, and suggest several PKCs can regulate PPARalpha activity through multiple phosphorylation sites.     

Fraenkel's pupariation factor identified at last

Thirty-five years ago, Zdarek and Fraenkel demonstrated that nervous tissue extracts influenced development by accelerating pupariation in the grey flesh fly, Neobellieria bullata. We have now identified this pupariation factor as SVQFKPRLamide, designated Neb-pyrokinin-2 (Neb-PK-2). To achieve this, the central nervous system of N. bullata wandering stage larvae, that is, preceding pupariation, were dissected and extracted before HPLC separation. Chromatographic fractions were screened with a bioassay for pupariation accelerating activity. Only one fraction showed huge pupariation activity. Mass spectrometry revealed the presence of a pyrokinin, whose primary sequence could not be unequivocally determined by tandem mass spectrometry. However, this Neb-pyrokinin appeared to be very prominent in the ring gland from which it was subsequently purified and identified. Synthetic Neb-PK-2 accelerates pupariation with a threshold dose of only 0.2 pmol and therefore, Neb-pyrokinin is considered to be the genuine pupariation factor. The immunohistochemical distribution pattern of Neb-PK-2 is very similar to that of Drosophila pyrokinin-2, from which it differs by only one amino acid residue. Hence, the recently identified G-protein coupled receptors (CG8784, CG8795) for Drosophila pyrokinin-2 might play an important role in puparium formation.     

Antioxidant effects of American ginseng berry extract in cardiomyocytes exposed to acute oxidant stress

It is postulated that antioxidant properties of American ginseng root mediate its cardioprotective actions. The antioxidant capabilities of the American ginseng root have been demonstrated previously, however, the berry of the American ginseng has not yet been evaluated. In this study, we tested the American ginseng berry extract (AGBE) for its antioxidant effects in cell-free chemical systems using H(2)O(2)/FeSO(4) to generate hydroxyl radicals which were measured by a fluorescent probe, 2', 7'-dichlorofluorescin diacetate (DCFH/DA). Xanthine/xanthine oxidase was used to generate superoxide anion, which was measured by a fluorescent probe dihydroethidium (DHE). We found that AGBE decreased fluorescence significantly, suggesting that AGBE scavenges oxygen free radicals. We further tested whether AGBE (0.1-1 mg/ml) can protect cardiomyocytes from oxidative injury induced by exogenous or endogenous oxidants. Cells were exposed to either H(2)O(2) or antimycin A (a mitochondrial electron transport chain site III inhibitor that augments mitochondrial oxidant production). The resulting oxidant stress was measured using DCFH/DA and the cell death was assessed using propidium iodide staining. Pretreatment with AGBE (1 mg/ml) significantly attenuated DCF fluorescence by 49% or 85% and reduced cell death by 59% or 63% in cells exposed to H(2)O(2) or antimycin A, respectively. When the effects of extracts from berry and root of American ginseng were compared in cardiomyocytes exposed to antimycin A, we observed that AGBE conferred greater antioxidant protection at the same dose. We conclude that AGBE is a potent antioxidant that protects cardiomyocytes against oxidant-mediated injury and this protection is partly mediated by its free radical scavenging properties.     

Substitution of conserved glycine residue by alanine in natural and synthetic neuropeptide ligands causes partial agonism at the stomoxytachykinin receptor

A few naturally occurring insect tachykinin-related peptides, such as stomoxytachykinin (Stc-TK), contain an Ala-residue instead of the highly conserved Gly-residue that is present in most other members of this peptide family. Stc-TK is a potent, partial agonist of the stable fly (Stomoxys calcitrans) tachykinin receptor, STKR. By means of synthetic analogues, the Gly/Ala exchange, representing the addition of a single methyl group in the active core region of these peptides, was shown to be fully responsible for the generation of this partial agonism, which was also accompanied by an increase in agonistic potency. Surprisingly, this Ala-dependent reduction in maximal response levels was only observed for the agonist-induced cellular calcium rise. Stomoxytachykinin, Stc-TK, did not display partial agonism for the STKR-mediated cyclic AMP response. A possible explanation for this differential partial agonism is that the Gly-containing and Ala-replaced peptides recognize and stabilize active receptor conformations that differ in their functional coupling efficacies towards these response pathways. Drosotachykinins, Drm-TK, tachykinin-like peptides encoded in the fruit fly genome, were shown to be STKR-agonists. Interestingly, one of these peptides, which contains an Ala-residue instead of the conserved Gly-residue, also proved to be a potent, partial agonist for STKR.     

Necrosis is associated with IL-6 production but apoptosis is not

Due to loss of cell membrane integrity, necrotic cells passively release several cytosolic factors that can activate antigen presenting cells and other immune cells. In contrast, cells dying by apoptosis do not induce an inflammatory response. Here we show that necrotic cell death induced by several stimuli, such as TNF, anti-Fas or dsRNA, coincides with NF-kappaB-and p38MAPK-mediated upregulation and secretion of the pro-inflammatory cytokine IL-6. This event is greatly reduced or absent in conditions of apoptotic cell death induced by the same stimuli. This demonstrates that besides the capacity of necrotic cells to induce an inflammatory response due to leakage of cellular contents, necrotic dying cells themselves are involved in the expression and secretion of inflammatory cytokines. Moreover, inhibition of NF-kappaB and p38MAPK activation does not affect necrotic cell death in all conditions tested. This suggests that the activation of inflammatory pathways is distinct from the activation of necrotic cell death sensu strictu.