查看更多>>摘要：Prophenoloxidase (PPO), an important immunity protein in insects, is mainly produced by hemocytes and released into the hemolymph upon cell lysis. In addition, PPO can also be produced by epidermal cells in the foregut to detoxify the toxic plant secondary metabolites and in the hindgut to kill pathogens through PPOinduced melanization. Previously, we noticed a pair of tubes extended from the larval hindgut became melanized upon staining in dopamine dissolved in 30% ethanol. However, the structure and function of these tubes are largely unknown. In this study, we performed staining of the tubes and the neighboring Malpighian tubule for further confirmation. Eventually, we detected PPO inside epidermal cells of the tubes, and called them as PPOpositive tubes. We observed that the PPO-positive tubes are physically derived from the hindgut but strongly adhere to the Malpighian tubule. Inside the PPO-positive tubes, there is an acellular peritrophic membrane to protect the epidermal cells. Furthermore, the PPO-positive tubes act like a doorkeeper to firstly detoxify the metabolite wastes collected by the Malpighian tubule from the hemolymph.
查看更多>>摘要：Toll-like receptors (TLRs) mediated signaling plays a vital role in activating innate and adaptive immunity. Although TLR mediated signaling has been comprehensively investigated in mammalian species, the mechanisms underlying TLR signaling in molluscs remain obscure. In the present study, a novel TLR isoform namely McTLRlike1 was identified in the thick shell mussel Mytilus coruscus. McTLR-like1 was highly expressed in molluscan immune-related tissues, and its transcriptional levels in hemocytes were significantly increased when challenged by V. alginolyticus. McTLR-like1 activated nuclear factor kappa B (NF-kappa B) and strengthened the transcription and phosphorylation of NF-kappa B subunit P65 in mammalian cells. Upon the silencing of McTLR-like1, the mRNA expression levels of pro-inflammatory cytokines were down-regulated, and the animals exhibited higher levels of resistance when challenged with V. alginolyticus. McMyD88a mRNA expression was also downregulated alongside McTLR-like1. Furthermore, GST-pull down assays revealed a visible affinity between McTLR-like1 and McMyD88a. Collectively, these results demonstrated that the newly identified gene affiliated to the molluscan TLR family and plays a role in the TLR-mediated activation of inflammatory response via its affinity with MyD88. The present study enhances our knowledge of TLR signaling mechanisms in molluscs and provides new insights into the evolution of TLRs.
查看更多>>摘要：As a representative species of Lepidoptera, Bombyx mori has been widely studied and applied. However, bacterial infection has always been an important pathogen threatening the growth of silkworms. Bombyx mori can resist various pathogenic bacteria through their own physical barrier and innate immune system. However, compared with other insects, such as Drosophila melanogaster, research on the antibacterial mechanism of silkworms is still in its infancy. This review systematically summarized the routes of bacterial infection in silkworms, the antibacterial mechanism of silkworms after ingestion or wounding infection, and the intestinal bacteria and infection of silkworms. Finally, we will discuss silkworms as a model animal for studying bacterial infectious diseases and screening antibacterial drugs.
查看更多>>摘要：Cathelicidins have antimicrobial and immunomodulatory activities. Previous studies have shown that chicken cathelicidin-2 (CATH-2) exerts strong anti-inflammatory activity through LPS neutralization. However, it is still unclear whether other intracellular signaling pathways are involved in CATH-2 immunomodulation. Therefore, the CATH-2-meadiated immune response was investigated in LPS-primed neutrophils. Firstly, inflammatory cytokines release was determined in LPS-primed neutrophils. The results showed that CATH-2 significantly promoted secretion of IL-1(i and IL-1 alpha while IL-6 and TNF-alpha were not affected. IL-1(i is the key indicator of inflammasome activation. Next, NLRP3 inflammasome signaling pathway was explored using neutrophils of Nlrp3- /-, Asc-/- and Casp1-/- mice and the results showed that the CATH-2-enhanced IL-1(i release was completely abrogated, indicating it is NLRP3-dependent. Moreover, CATH-2 significantly induced activation of caspase-1 and gasdermin D (GSDMD) but did not affect LPS-induced mRNA expression of IL-1(i and NLRP3, demonstrating that CATH-2 serves as the second signal activating the NLRP3 inflammasome. Furthermore, CATH-2-mediated IL-1(i secretion and caspase-1 activation is dependent on potassium efflux but independent of P2X7R. In addition, other signaling pathways including JNK, ERK and SyK were investigated using different inhibitors and the results showed that these signaling pathway inhibitors partially attenuated CATH-2-enhanced IL-1(i secretion, especially the JNK inhibitor. Finally, the role of serine protease in CATH-2-mediated NLRP3 inflammasome activation was investigated in neutrophils and the results showed that serine protease activity is involved in CATH-2-enhanced IL-1(i secretion and caspase-1 activation. In conclusion, after LPS priming in neutrophils, CATH-2 can be an agonist of the NLRP3 inflammasome. Our study increases the understanding on immunomodulatory effects of chicken cathelicidins and provides new insight on chicken cathelicidins-mediated immune response.
查看更多>>摘要：Inflammatory cytokine interleukin-17 (IL-17) binds its receptors (IL-17Rs) to activate the downstream immune signals and plays an important role in host defense. In the present study, an IL-17 receptor (designated as CgIL-17R1) was identified from oyster Crassostrea gigas with an open reading frame of 3141 bp encoding 1047 amino acids. The amino acid sequence of CgIL-17R1 with two conserved FN3 domains shared higher similarity with other known IL-17Rs from mollusc species. The recombinant CgIL-17R1 protein (rCgIL-17R1) displayed high binding affinity to the recombinant CgIL-17 protein (rCgIL-17) in vitro. The mRNA transcripts of CgIL-17R1 were significantly higher expressed in haemocytes, especially in granunolyctes, compared with that in other tissues. After the stimulation with Vibrio splendidus or rCgIL17-1 in vivo, the expressions of CgIL-17R1 and cell proliferation related genes (CgRunx-1, CgCDC-6, CgCDC-45, and CgCDK-2) were significantly up-regulated in haemocytes (p < 0.01). When the CgIL-17R1 expression was interfered by specific CgIL-17R1-dsRNA, the expressions of these cell proliferation related genes reduced significantly, and the proliferation rate of haemocytes declined dramatically at 6 h post V. splendidus stimulation (p < 0.01), compared to that of blank group. These results collectively indicated that CgIL-17R1 expressed in granulocytes mediated the CgIL-17 induced haemocytes proliferation during immune response in oyster C. gigas, which provided novel information about the regulation of haemocyte proliferation in invertebrates.
查看更多>>摘要：Penaeus vannamei is an important cultured shrimp that has high commercial value in the worldwide. However, the industry suffers heavy economic losses each year due to disease outbreaks caused by pathogenic bacteria. In the present study, after Vibrio alginolyticus infection, DNA damage in the hemocytes of the shrimp markedly increased, and autophagy and apoptosis increased significantly. Subsequently, hemocytes were sampled from the control and infected shrimp and sequenced for mRNA and microRNA (miRNA) 24 h after V. alginolyticus infection to better understand the response mechanism to bacterial infection in P. vannamei. We identified 1,874 and 263 differentially expressed mRNAs (DEGs) and miRNAs (DEMs) respectively, and predicted that 997 DEGs were targeted by DEMs. These DEGs were involved in the regulation of multiple signalling pathways, such as Toll and IMD signalling, TGF-beta signalling, MAPK signalling, and cell apoptosis, during Vibrio alginolyticus infection of the shrimp. We identified numerous mRNA-miRNA interactions, which provide insight into the defense mechanism that occur during the antimicrobial process of P. vannamei.
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Elsevier