Lipoxin A(4) attenuates zymosan-induced arthritis by modulating endothelin-1 and its effects

BACKGROUND AND PURPOSE

Lipoxin A(4) (LXA(4)) is a lipid mediator involved in the resolution of inflammation. Increased levels of LXA(4) in synovial fluid and enhanced expression of the formyl peptide receptor 2/lipoxin A(4) receptor (FPR2/ALX) in the synovial tissues of rheumatoid arthritis patients have been reported. Endothelins (ETs) play a pivotal pro-inflammatory role in acute articular inflammatory responses. Here, we evaluated the anti-inflammatory role of LXA(4), during the acute phase of zymosan-induced arthritis, focusing on the modulation of ET-1 expression and its effects.

EXPERIMENTAL APPROACH

The anti-inflammatory effects of LXA(4), BML-111 (agonist of FPR2/ALX receptors) and acetylsalicylic acid (ASA) pre- and post-treatments were investigated in a murine model of zymosan-induced arthritis. Articular inflammation was assessed by examining knee joint oedema; neutrophil accumulation in synovial cavities; and levels of prepro-ET-1 mRNA, leukotriene (LT)B(4), tumour necrosis factor (TNF)-α and the chemokine KC/CXCL1, after stimulation. The direct effect of LXA(4) on ET-1-induced neutrophil activation and chemotaxis was evaluated by shape change and Boyden chamber assays respectively.

KEY RESULTS

LXA(4), BML-111 and ASA administered as pre- or post-treatment inhibited oedema and neutrophil influx induced by zymosan stimulation. Zymosan-induced preproET-1 mRNA, KC/CXCL1, LTB(4) and TNF-α levels were also decreased after LXA(4) pretreatment. In vitro, ET-1-induced neutrophil chemotaxis was inhibited by LXA(4) pretreatment. LXA(4) treatment also inhibited ET-1-induced oedema formation and neutrophil influx into mouse knee joints.

CONCLUSION AND IMPLICATION

LXA(4) exerted anti-inflammatory effects on articular inflammation through a mechanism that involved the inhibition of ET-1 expression and its effects.

Antiinflammatory effects of natural tetranortriterpenoids isolated from Carapa guianensis Aublet on zymosan-induced arthritis in mice

OBJECTIVE

We investigated the antiinflammatory properties of a derived fraction of tetranortriterpenoids (TNTP) obtained from the seeds of Carapa guianensis Aublet.

MATERIAL AND METHODS

Zymosan-induced arthritis and pleurisy in Swiss and C57/Bl6 mice (n = 10 per group). Western blot analysis was performed to analyze nuclear factor-kappaB (NFkappaB) translocation in mice peritoneal macrophages stimulated in vitro with zymosan (500 microg/ml). ELISA was performed to evaluate cytokine levels in knee joints. Values of p </= 0.05 were regarded as significant.

RESULTS

Zymosan intra-articular (i. a.) injection (500microg/ cavity) induced a significant increase in knee joint diameter within 6 h, peaked within 24 h and remained above control values for 20 days. Orally-given (p. o.) TNTP (100-200 mg/ kg) inhibited zymosan-induced increase in knee joint diameter and protein extravazation into synovial cavity within 6 h. TNTP (100-200 mg/kg, p. o.) also inhibited total leukocyte influx into the synovial space and tissue, as well as into the mice pleural cavity, due to neutrophil impairment 6 h after zymosan stimulation. The increase in TNF-alpha, IL-1beta and CXCL8/IL-8 levels that were detected in knee synovial extracts obtained from zymosan-stimulated mice was also inhibited by TNTP (100 mg/kg, p. o.). Moreover, the incubation of mice peritoneal macrophages with TNTP (100 mug/ml) inhibited zymosan (500 microg/ml)-induced NFkappaB translocation into the nucleus 6 h after stimulation.

CONCLUSION

Taken together, these results indicate that TNTP present an important antiinflammatory effect, inhibiting zymosan-induced arthritis in mice via the impairment of TNF-alpha, IL-1beta and CXCL8/IL-8 generation, as well as NFkappaB signaling pathway.

Activity of liver microsomal enzymes during the chronic phase of murine schistosomiasis

The effects of schistosomiasis on microsomal enzymes were studied on post-infection day 90 when accumulated damage and fibrosis are most intense but granulomatous reaction around the eggs harbored in the liver is smaller than during the earlier phases. Swiss Webster (SW) and DBA/2 mice of either sex (N = 12 per sex per group) were infected with 100 Schistosoma mansoni cercariae on postnatal day 10 and killed on post-infection day 90. Cytochrome P-450 (CYP) concentration and alkoxyresorufin-O-dealkylases (EROD, MROD, BROD, and PROD), p-nitrophenol-hydroxylase (PNPH), coumarin-7-hydroxylase (COH), and UDP-glucuronosyltransferase (UGT) activities were measured in hepatic microsomes. Age-matched mice of the same sex and strain were used as controls. In S. mansoni-infected mice, CYP1A- and 2B-mediated activities (control = 100%) were reduced in SW (EROD: male (M) 36%, female (F) 38%; MROD: M 38%, F 39%; BROD: M 46%, F 19%; PROD: M 50%, F 28%) and DBA/2 mice (EROD: M 64%, F 58%; MROD: M 60%; BROD: F 49%; PROD: M 73%) while PNPH (CYP2E1) was decreased in SW (M 31%, F 38%) but not in DBA/2 mice. COH did not differ between infected and control DBA/2 and UGT, a phase-2 enzyme, was not altered by infection. In conclusion, chronic S. mansoni infection reduced total CYP content and all CYP-mediated activities evaluated in SW mice, including those catalyzed by CYP2E1 (PNPH), CYP1A (EROD, MROD) and 2B (BROD, PROD). In DBA/2 mice, however, CYP2A5- and 2E1-mediated activities remained unchanged while total CYP content and activities mediated by other CYP isoforms were depressed during chronic schistosomiasis.

Morphology of isolated crustacean larval salt glands

Larval salt glands isolated from the naupliar brine shrimp (Artemia salina) were examined using light microscopy and scanning and transmission electron microscopy. These methods demonstrated that most cellular and subcellular features of the in vitro organ compared favorably with those seen in vivo. This salt gland measures 130 micron in diameter and is comprised of 50-70 secretory cells, which are of a single epithelial cell type. Characteristic ultrastructural features that are well preserved include apical to basal cell polarity, apical plasma membrane projections, and the extent of the basolateral tubular labyrinth and its association with numerous mitochondria. Some features that have been altered are a decrease in cell-cell contact, separation of septate junctions, and expansion of tubular labyrinth lumens and mitochondrial cristae. Use of this preparation has allowed examination of the salt gland cell's hemocoelic surface for the first time and provided information about the ultrastructure of the tufts formed by the apical plasma membrane.

Isolation and functional characterization of crustacean larval salt gland

A batch method for isolating viable salt glands from the naupliar brine shrimp (Artemia salina) has been developed. This protocol produces a final preparation consisting of approximately 185 isolated salt glands, representing 1 X 10(4) secretory cells/g wet wt nauplii, with a final purity of 88%. Assays of cell integrity and function indicate good retention of in situ characteristics. Vital dye was excluded by 95% of the cells for at least 24 h. The O2 consumption rate was 22.7 nM O2 X min-1 X mg protein-1 and could be altered predictably by compounds known to affect oxidative phosphorylation and ion transport. The specific activity of the Na+-K+-ATPase in the salt gland, measured here for the first time, was 9.1 mM Pi X h-1 X mg protein-1. This is a substantial proportion of the body total, 17%, as expected for an active ion-transporting epithelium.

Larval brine shrimp malate dehydrogenase: biosynthesis and temporal pattern related to environmental salinity

Brine shrimp nauplii challenged with artificial sea water containing 2.5 M NaCl maintain significantly higher levels of cytoplasmic malate dehydrogenase (s-MDH) than larvae incubated in sea water having 0.5 M NaCl. Eight to ten hours after emergence, free-swimming nauplii living in 0.5 M NaCl exhibit a steady decline of s-MDH for 20-40 hours; the decreased is less and stabilizes earlier-in nauplii incubated in 2.5 M NaCl. The 14C-labeled amino acids produced by H 14CO3 fixation were rapidly incorporated into newly formed s-MDH protein as assayed using quantitative rocket immunoelectrophoresis (IEP) with monospecific antiserum prepared against purified brine shrimp s-MDH. Higher rates of enzyme biosynthesis ( greater than 45%) occurred in 2.5 M NaCl together with rapid s-MDH turnover (half-life = 17 hours), accounting for the difference observed in enzyme level between different salt regimes. In contrast, incorporation of 14C-labeled amino acids into total cytoplasmic protein decreased slightly in high salt, suggesting that a preferential synthesis of s-MDH is taking place. Temporal patterns of s-MDH during embryonic development were monitored using both catalytic activity and quantitative IEP assays. Levels of s-MDH seen in encysted gastrulae (0.22 units or 0.57 microgram s-MDH protein/100 embryos) remain relatively constant through the E1 and E2 emergent stages until the exhibited decline observed in the naupliar stage. The results are discussed in relation to the bioenergetics and temporal development of water and electrolyte regulation in nauplii.

Immunochemical characterization and quantification of larval brine shrimp malate dehydrogenase

The cytosolic malate dehydrogenase (s-MDH) from larval brine shrimp has been immunochemically characterized by quantitative rocket immunoelectrophoresis (IEP) and antibody catalytic inhibition studies. Monospecific rabbit antiserum produced against purified naupliar s-MDH was used for rocket IEP as a quantitative assay for the cytoplasmic isozyme, Since cross-reactivity was not observed against the mitochondrial MDH (m-MDH), the assay allows specific measurement of the s-MDH in crude naupliar supernatants in the presence of contaminating m-MDH. The assay has a sensitivity of approximately 100 nanograms s-MDH protein using either purified enzyme solutions or crude supernatant preparations. Catalytic inhibition studies using the monospecific antiserum gave 85% inhibition of s-MDH but did not give significant inhibition of the m-MDH. Lack of complete s-MDH inhibition by the antiserum suggests a difference between the enzyme active site and immunological binding site. Although the antiserum was produced against s-MDH from nauplii of the San Francisco Bay population, the antiserum inhibits equally well the s-MDH of Great Salt Lake (Utah) nauplii, indicating little if any structural difference in the immunological sites of the s-MDHs from these two geographical sources. Porcine (s- and m-MDH), bovine (m-MDH), and pigeon (m-MDH) were also tried as antigens against the brine shrimp s-MDH antiserum, but antigen-antibody reactivity was not observed during rocket IEP or catalytic inhibition experiments.

Role of C-4 pathway in crustacean chloride cell function

A hypothetical model for the bioenergetic regulation of ion transport in the chloride cell of the larval crustacean salt gland is presented. Current data dealing with the ultrastructural, electrochemical, and biochemical events associated with cytodifferentiation of the crustacean (Artemia salina) salt-excreting epithelia is compiled and tabulated. A C-4 dicarboxylic aicd pathway is postulated to serve as a facultative anaerobic shunt to meet the demands of the high rate of glycolysis required by salt-secreting epithelium. This mechanism involves the fixation of CO2 from exogenous bicarbonate while forming net amounts of metabolic water and high energy nucleotide equivalents from stored diGDP.

Regulation of nucleic acid synthesis in Artemia salina nauplii by environmental salinity

Ribonucleic acid synthesis in Artemia salina nauplii was strongly inhibited by increasing salinity in the surrounding media, as measured by incorporation of tritiated uridine. Although precursor pools varied in both concentration and specific activity with increasing salinity, these changes did not account for the reduction in ribonucleic acid synthesis. Low levels of oxygen at high salt concentrations did not account for this effect. Intracellular ATP concentrations decreased as the salinity of the environment was increased. Levels of ATP were not affected either by increased oxygen or by the presence of ouabain in the medium.

Molecular aspects of chloride cell formation in Oncorhynchus. II. Isolation and characterization of gill transfer RNA's during active salt secretion

The transfer ribonucleic acids (tRNAs) from gill filaments of coho salmon, Oncorynchus kisutch, have been isolated and were separated into individual species of acceptor tRNAs by reversed-phase column chromotography. Crude tRNAs isolated from gill filaments undergoing active salt excretion were acrylated with 14C-amino acids and combined with tRNAs acylated with 3H-amino acids, but obtained from non-secreting filaments. The radioactively labeled tRNA mixture was cochromatographed and the results showed significant differences in the elution profiles of tRNAasp and tRNAtyr. These elution profiles may reflect the differentiation of the chloride cell population that is found within the gill epithelium.

Molecular aspects of chloride cell formation in Oncorhynchus. I. Isolation and characterization of ribosomes involved in protein synthesis

The present investigation has developed techniques for the reproducible isolation of polyribosomes from gill filaments of Oncorhynchus nerka, O. kisutch, O. tshawytscha, and Salmo gairdneri. A basic pattern of aggregated complexes was resolved in microsomal and deoxycholate-treated fractions that was consistent with the ultrastructural observations made by electron microscopy. The relative amino acid incorporating activity was assessed in vivo and the association with particular polyribosomal classes was made. Gill filaments undergoing active salt secretion have smaller polysomes involved in protein synthesis than non-secreting gill filaments. Increased protein synthesis appears correlated with development of chloride cells.

CELLULAR RENEWAL OF INTESTINAL EPITHELIUM IN THE WESTERN FENCE LIZARD, SCELOPORUS OCCIDENTALIS

The renewal rate of intestinal epithelial cells in the lizard Sceloporus occidentalis has been studied by utilizing the colchicine mitotic inhibiting technique and radioautography with tritiated thymidine.The sites of DNA synthesis, cell proliferation, cell migration, turnover time, mitotic duration, and generation cycle have been determined at 26 °C or 21 °C for juvenile and adult lizards.Cell proliferation occurred in basal regions of the longitudinal folds of the small intestine and at the base of each secondary fold in the large intestine. Cell migration, as evidenced by labeled cells, occurred by transposition of the epithelial cells from the basal proliferative zones onto the folds, with subsequent migration up the folds and final sloughing at the tips of the folds. The cellular turnover time in the juvenile lizards was 5 to 7 days, and 6 to 9 days in the adult lizards.The average mitotic indices for the intestinal epithelial cells were 0.013 and 0.017 for the adults and juveniles, respectively. The mitotic duration was 1.8 hours and the generation cycle was estimated to be 20 to 22 hours.