HMGB in mollusk Crassostrea ariakensis Gould: structure, pro-inflammatory cytokine function characterization and anti-infection role of its antibody

An insight of anopheline larvicidal mechanism of Trichoderma asperellum (TaspSKGN2)

Anopheline larvicidal property of T. asperellum has been found recently in medical science. The mechanism of actions exhibited by T. asperellum to infect mosquito larvae is the pivotal context of our present study. To infect an insect, entomopathogens must undergo some events of pathogenesis. We performed some experiments to find out the mechanisms of action of T. asperellum against anopheline larvae and compared its actions with other two well recognized entomopathogens like Metarhizium anisopliae and Beauveria bassiana. The methodology adopted for this includes Compound light and SE Microscopic study of host-pathogen interaction, detection of fungal spore adhesion on larval surface (Mucilage assay), detection of cuticle degrading enzymes (Spore bound pr1, chitinase and protease) by spectro-photometric method, Quantitative estimation of chitinase and protease enzymes, and determination of nuclear degeneration of hemocyte cells of ME (methanolic extract) treated larvae by T. asperellum under fluorescence microscope. Compound light microscopic studies showed spore attachment, appressorium and germ tube formation, invasion and proliferated hyphal growth of T. asperellum on epicuticle and inside of dead larvae. SEM study also supported them. After 3 h of interaction, spores were found to be attached on larval surface exhibiting pink colored outer layer at the site of attachment indicating the presence of mucilage surrounding the attached spores. The enzymatic cleavage of the 4-nitroanilide substrate yields 4-nitroaniline which indicates the presence of spore-bound PR1 protein (Pathogenecity Related 1 Protein) and it was highest (absorbance 1.298 ± 0.002) for T. asperellum in comparison with control and other two entomopathogens. T. asperellum exhibited highest enzymatic index values for both chitinase (5.20) and protease (2.77) among three entomopathogens. Quantitative experiment showed that chitinase enzyme concentration of T. asperellum (245 µg mL^-1) was better than other two M. anisopliae (134.59 µg mL^-1) and B. bassiana (128.65 µg mL^-1). Similarly protease enzyme concentration of this fungus was best (298.652 µg mL^-1) among three entomopathogens. Here we have detected and estimated fragmentized nuclei of hemocyte cells by fluorescence microscopy in treated larvae with different ME doses of T. asperellum, and also observed that mosquito larvae exposed to 0.1 mg mL^-1 dose of ME showed maximum (100%) nuclear fragmentations of hemocytes and while 20, 45, 70 and 85% of nuclear deformities were recorded at 0.02, 0.04, 0.06 and 0.08 mg mL^-1 concentrations of ME. The knowledge of this work certainly will help in understanding of mechanism of action of T. asperellum for anopheline larval killing and consequently in eradication of malaria vector.

Silver nanoparticle-induced developmental inhibition of Drosophila melanogaster accompanies disruption of genetic material of larval neural stem cells and non-neuronal cells

A few studies had determined the effects of silver nanoparticles on the development of Drosophila melanogaster. However, none had addressed its genotoxic effects on specific larval cells of the fly in details. This study was conducted to determine the effects of silver nanoparticle on the development of D. melanogaster with simultaneous evaluation of its genotoxic potential on specific larval cell types that play important roles in immunological defenses as well as growth and development. Five male and five female flies were maintained in standard Drosophila melanogaster culture medium containing varying concentrations of silver nanoparticles, i.e., 25, 50, 100, 200, and 300 mg/l with control culture medium containing no nanoparticle. Total time needed for stage-specific development, population yield, and genotoxic effects on third instar larval polytene chromosomes, hemocytes, and neuroblasts was determined. Body pigmentation of pupae and young adults was examined visually. In comparison with control, silver nanoparticles dose dependently inhibited the metamororphosis and population yields of pupae and young adults of Drosophila melanogaster. Every concentration of the nanoparticles inhibited pupa to adult conversion, with huge reduction under the influence of nanoparticle concentration of 100 mg/ml and above. Developmental inhibition was accompanied by dose-dependent and significant structural aberrations of larval polytene chromosomes and deformities of hemocytes and neuroblasts. Pupae and young adults also exhibited gradual discoloration of body with the increase in exposure to nanoparticle concentration.

First characterization of three cyclophilin family proteins in the oyster, Crassostrea ariakensis Gould

Cyclophilins (CyPs) are a family of proteins that bind the immunosuppressive agent cyclosporin A (CsA) with high-affinity and belong to one of the three superfamilies of peptidyl-prolyl cis-trans isomerases (PPIase). In this report, three cyclophilin genes (Ca-CyPs), including Ca-CyPA, Ca-CyPB and Ca-PPIL3, were identified from oyster, Crassostrea ariakensis Gould in which Ca-CyPA encodes a protein with 165 amino acid sequences, Ca-CyPB encodes a protein with 217 amino acid sequences and Ca-PPIL3 encodes a protein with 162 amino acid sequences. All of the three Ca-CyPs genes contain a typical CyP-PPIase domain with its signature sequences and Ca-CyPB contains an N-signal peptide sequences. Tissue distribution study revealed that Ca-CyPs were ubiquitously expressed in all examined tissues and the highest levels were observed in hemocytes. RLO incubation upregulated the mRNA expression levels of Ca-CyPs, indicating that three Ca-CyPs might be involved in oyster immune response against RLO infection.

Identification and expression analysis of lipopolysaccharide-induced TNF-alpha factor gene in Chinese mitten crab Eriocheir sinensis

Lipopolysaccharide-induced TNF-alpha factor (LITAF) is an important transcription factor in transcriptional regulation of TNF-alpha and other cytokines. Here we identified a full-length LITAF homolog cDNA, termed EsLITAF, that contains a 71 bp 5'-untranslated sequence, an open reading frame consisting of 381 bp, and a 208 bp 3'-untranslated sequence in Chinese mitten crab (Eriocheir sinensis), an economically important freshwater crustacean species in China. EsLITAF protein possesses a conserved C-terminal LITAF-like domain with two CXXC motifs and is comprised of 126 amino acids with a theoretical molecular mass of 13.1 kDa and an isoelectric point of 6.36. Blast search against GenBank database revealed that EsLITAF protein shared the highest sequence identity (84%) with the counterpart of Pacific white shrimp (Litopenaeus vannamei). EsLITAF mRNA transcript expresses ubiquitously in all examined tissues with the highest expression in hepatopancreas and lowest expression in haemocytes. Furthermore, EsLITAF mRNA expression could be significantly and rapidly induced in haemocytes by LPS and Poly(I:C) stimulations in vitro. Moreover, EsLITAF gene expression was up-regulated in haemocytes, gill and hepatopancreas after Edwardsiella tarda and Vibrio anguillarum challenges. Taken together, we have identified and characterized a new crustacean LITAF homolog from the Chinese mitten crab.

allograft inflammatory factor 1 functions as a pro-inflammatory cytokine in the oyster, Crassostrea ariakensis

The oyster Crassostrea ariakensis is an economically important bivalve species in China, unfortunately it has suffered severe mortalities in recent years caused by rickettsia-like organism (RLO) infection. Prevention and control of this disease is a priority for the development of oyster aquaculture. Allograft inflammatory factor-1 (AIF-1) was identified as a modulator of the immune response during macrophage activation and a key gene in host immune defense reaction and inflammatory response. Therefore we investigated the functions of C. ariakensis AIF-1 (Ca-AIF1) and its antibody (anti-CaAIF1) in oyster RLO/LPS-induced disease and inflammation. Ca-AIF1 encodes a 149 amino acid protein containing two typical Ca2+ binding EF-hand motifs and shares a 48-95% amino acid sequence identity with other animal AIF-1s. Tissue-specific expression analysis indicates that Ca-AIF1 is highly expressed in hemocytes. Significant and continuous up-regulation of Ca-AIF1 is detected when hemocytes are stimulated with RLO/LPS (RLO or LPS). Treatment with recombinant Ca-AIF1 protein significantly up-regulates the expression levels of LITAF, MyD88 and TGFβ. When anti-CaAIF1 antibody is added to RLO/LPS-challenged hemocyte monolayers, a significant reduction of RLO/LPS-induced LITAF is observed at 1.5-12 h after treatment, suggesting that interference with Ca-AIF1 can suppress the inflammatory response. Furthermore, flow cytometric analysis indicated that anti-CaAIF1 administration reduces RLO/LPS-induced apoptosis and necrosis rates of hemocytes. Collectively these findings suggest that Ca-AIF1 functions as a pro-inflammatory cytokine in the oyster immune response and is a potential target for controlling RLO infection and LPS-induced inflammation.

A high mobility group box 1 (HMGB1) gene from Chlamys farreri and the DNA-binding ability and pro-inflammatory activity of its recombinant protein

High-mobility group box 1 (HMGB1) protein, a highly conserved DNA binding protein, plays an important role in maintaining nucleosome structures, transcription, and inflammation. In the present research, a cDNA of 1268 bp for the Zhikong scallop Chlamys farreri HMGB1 (designed as CfHMGB1) was cloned via rapid amplification of cDNA ends (RACE) technique and expression sequence tag (EST) analysis. The complete cDNA sequence of CfHMGB1 contained an open reading frame (ORF) of 648 bp, which encoded a protein of 215 amino acids. The amino acid sequence of CfHMGB1 shared 53-57% similarity with other identified HMGB1s. There were two HMG domains, two low complexity regions and a conserved acidic tail in the amino acid sequence of CfHMGB1. The mRNA transcripts of CfHMGB1 were constitutively expressed in all the tested tissues, including haemocytes, muscle, mantle, gill, hepatopancreas, kidney and gonad, with the highest expression level in hepatopancreas. The mRNA expression profiles of CfHMGB1 in haemocytes after the stimulation with different pathogen-associated molecular patterns (PAMPs), including lipopolysaccharide (LPS), peptidoglycan (PGN) and glucan (Glu), were similar with an up-regulation in the early stage and then recovered to the original level. The recombinant CfHMGB1 protein could bind double-stranded DNA and induce the release of TNF-α activity in mixed primary culture of scallop haemocytes. These results collectively indicated that CfHMGB1, with DNA-binding ability and pro-inflammatory activity, could play an important role in the immune response of scallops.

High mobility group box 1 can enhance NF-κB activation and act as a pro-inflammatory molecule in the Pacific oyster, Crassostrea gigas

High-mobility group box 1 (HMGB1), a highly conserved DNA-binding protein, is involved in nucleosome formation and transcriptional regulation, and can also act as an extracellular cytokine to trigger inflammation and immune responses. In this study, we identified a HMGB1 gene (hereafter designated as CgHMGB1) in the Pacific oyster Crassostrea gigas. The full-length CgHMGB1 cDNA is 833 bp including 5' and 3'-untranslated regions (UTRs) of 145 and 79 bp, respectively, and an open reading frame (ORF) of 609 bp. The gene encodes a 202 amino acid polypeptide with an estimated molecular mass of 23.3 kDa. Sequence alignment shows that CgHMGB1 contains two basic HMG boxes and a highly acidic C-terminal domain. Recombinant CgHMGB1 proteins can enhance the mRNA level of various inflammatory cytokines in vivo. Typically, CgHMGB1 is localized in the nucleus, though lipopolysaccharide can induce its release to cytoplasm. Moreover, luciferase reporter assays reveal that CgHMGB1 cannot stimulate Nuclear Factor-κB reporter activity alone, but it can enhance Rel-dependent NF-κB activation in a dose-dependent manner. CgHMGB1 is highly expressed in hemocytes and its transcripts are significantly more abundant following bacterial challenge. Our results suggest that CgHMGB1 plays an essential role in innate defense by enhancing Rel-activated NF-κB activity and inducing the expression of inflammatory cytokines.