Molecular cloning and identification of macrophage migration inhibitory factor (MIF) in teleost fish

Macrophage migration inhibitory factor is vital for inflammatory properties and survival of peripheral blood leukocytes via enhancing mitochondrial function in Ctenopharyngodon idellus

Macrophage migration inhibitory factor (MIF) is a pleiotropic protein implicated in a broad spectrum of inflammatory and proliferative disorders. The gene sequence of grass carp (Ctenopharyngodon idella) was identified and the expression level of it was regulated by cadmium exposure in our previous study. To further clarify the immune-regulatory activity of grass carp MIF, MIF was over-expressed and interfered in grass carp peripheral blood leukocytes via transfection of plasmids pcDNA3.1-MIF-EGFP and pLKO.1-shRNA-EGFP-puro, respectively. Subsequently, survival, phagocytic capacity, mitochondrial function and cytokine production of the transfected leukocytes were assayed. The results shown that grass carp MIF was necessary for leukocyte survival, because it enhanced leukocyte viability and inhibited cell apoptosis, while MIF interference disrupted the cell viability and induced leukocyte apoptosis. The effect might benefit from improved mitochondrial function as evidenced by increased ATP production, which was due to maintained mitochondrial trans-membrane potential. In addition, MIF is essential for neutral red uptake into leukocyte, and it provoked chemokine monocyte chemotactic protein-1 (MCP-1), pro-inflammatory cytokine tumor necrosis factor-alpha (TNFα), interleukin 1β (IL1β), interleukin 6 (IL6), interleukin 8 (IL8), and suppressed anti-inflammatory cytokine interleukin 10 (IL10) production. These results indicated that grass carp MIF played a vital role in regulating inflammatory properties and survival of peripheral blood leukocytes.

CD4-1 and CD8α T lymphocytes subsets in spotted sea bass (Lateolabrax maculatus) and comparison on antigenicity of T lymphocytes subsets in other three marine fish species

CD4 and CD8 molecules play an important role in the identification of T lymphocytes, and diverse among fish species. In this study, CD4-1 and CD8α gene of spotted sea bass (Lateolabrax maculatus) were cloned, polyclonal antibodies against CD4-1 (CD4-1 pAbs) and CD8α (CD8α pAbs) were produced, respectively. And the variations in CD4-1⁺ and CD8α⁺ T-lymphocytes in spotted sea bass and the cross-reactivity with leukocytes in pearl gentian grouper (Epinephelus fuscoguttatus x E. lanceolatus), schlegel's black rockfish (Sebastes schlegelii) and flounder (Paralichthys olivaceus) were investigated using CD4-1 pAbs and CD8α pAbs. The results showed that CD4-1 molecule ORF was 1413 bp and CD8α was 690 bp, both molecules are transmembrane glycoproteins with high amino acid homology to grouper. The CD4-1 pAbs specifically recognized both the CD4-1 recombinant and natural proteins, as does the CD8α pAbs to CD8α molecule, and no cross-reactivity between the two antibodies. CD4-1⁺ and CD8α⁺ T lymphocytes were detected in peripheral blood, spleen and head kidney leukocytes in spotted sea bass. In cross-reactivity assay with other three fish, CD4-1 pAbs could recognize the lymphocytes from pearl gentian grouper and schlegel's black rockfish, both with highest proportions in the spleen leukocytes, 5.3 ± 0.4% and 2.6 ± 0.3%, respectively, and CD8α pAbs could only recognize the lymphocytes in pearl gentian grouper, and no cross-reactivities to lymphocytes of flounder. These data suggested that the CD4-1 and CD8α molecules varied by fish species in the genes features and antigenicity, which might result in the diversities of T lymphocytes subpopulations. This will be a key to elucidating the classification and evolution of T lymphocytes in fish.

Macrophage migration inhibitory factor (MIF) of golden pompano (Trachinotus ovatus) is involved in the antibacterial immune response

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine with a unique structure involved in immune regulation and inflammation. In the present study, we identified a MIF from Trachinotus ovatus (golden pompano) and analyzed its function. TroMIF shares high homology (58.26%-94.78%) with the other known MIF sequences of vertebrates. TroMIF is most closely related to large yellow croaker (Larimichthys crocea). The expression of TroMIF was most abundant in the liver and head kidney, and was significantly up-regulated after Edwardsiella tarda infection. The subcellular localization of TroMIF was mostly distributed in the cytoplasm. In vitro results revealed that the recombinant protein rTroMIF could inhibit the migration of head kidney lymphocytes (HKLs) and macrophages (HKMs) and enhance the phagocytic activity of HKMs. As a pro-inflammatory cytokine, rTroMIF could increase the expression levels of some pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin 1-beta (IL-1β), IL-6, IL-8, and interferon-gamma (IFN-γ) and decrease the expression of IL-10. The rTroMIF was proved to have enzymatic redox activity in vitro. Furthermore, overexpression of TroMIF in the head kidney cell line of golden pompano could significantly enhance its ability to resist E. tarda infection from 1 h to 4 h. The knockdown of TroMIF expression induced a significant increase in the number of bacteria after E. tarda infection at 1, 2, and 4 hpi. Our results suggest that TroMIF is an essential effector of the innate immune system and plays a pivotal role in antibacterial immunity.

Identification and immunologic property of macrophage migration inhibitory factor (MIF) in grass carp (Ctenopharynogodon idella)

Macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine, plays an important regulatory role in the activation of T cells induced by mitogenic or antigenic stimuli. However, the immunologic property of MIF in freshwater fish is limitedly known by now. In the present study, MIF gene was identified in grass carp. Bioinformatics analysis revealed that the molecular weight of grass carp MIF protein was 12.377 kDa and it could also bind to CD74. MIF gene was predominantly expressed in immune tissues including spleen and head kidney, then liver, skin, gill, intestine and blood, while a relative low level expression in heart, brain, fat and red muscle. The predicted receptor and tissues distribution of MIF implied the immunologic activity of grass carp MIF. Then grass carp MIF antigen and the polyclonal antibodies against it were prepared. Using cadmium as an immunosuppressive agent, MIF expression in spleen and head kidney was depressed in a dose-dependent manner with cadmium consumption. On the same time, white blood cell count decrease displayed a similar pattern with MIF expression, which suggested a possible positive correlation between MIF and white blood cell count. Thereafter, MIF enhanced the viability of grass carp peripheral blood leukocytes and inhibited cell apoptosis with depressed reactive oxygen species production in vitro. In addition, recombinant grass carp MIF promoted tumor necrosis factor-alpha (TNF-α), interleukin 1β (IL1β) and interleukin 6 (IL6) secretion from peripheral blood leukocytes. These results indicated the immunologic property of grass carp MIF.

Characterization and expression of macrophage migration inhibitory factor (mif) in Chinese sturgeon (Acipenser sinensis)

The Chinese sturgeon (Acipenser sinensis) is one of the critically endangered aquatic species in China. It is also among the oldest extant actinopterygian fish species. To advance the characterization of the Chinese sturgeon immune system, we identified the gene encoding the macrophage migration inhibitory factor (MIF), a multifunctional cytokine that contributes to both innate and adaptive immune responses. Molecular and phylogenic analysis indicates the Chinese sturgeon (cs) MIF share a high degree of structural conservation with other MIF sequences and is closely related to other bony fish MIF. At steady state, cs-mif gene is expressed at relatively high levels in the brain, and to a lesser but significant level in liver, spleen, kidney, gut and skin. The spatial expression patterns determined by in situ hybridization indicates a preferential distribution of cs-mif transcripts in the cerebral cortex, the gut epithelium, hematopoietic tissues of kidney, spleen and liver parenchyma, and skin epidermis. Marked increase of cs-mif gene expression was induced by lipopolysaccharide (LPS) stimulation and Aeromonas hydrophila infection in all tested tissues. Furthermore, higher cs-mif transcript levels were detected in the liver, spleen, kidney, gut and skin during stress response resulting from hyperthermia. These results are not only consistent with the expected role of cs-mif gene in innate immunity but also suggest a potential role of this gene in stress response to hyperthermia in the Chinese sturgeon.

D-dopachrome tautomerase from Japanese sea bass ( Lateolabrax japonicus) is a chemokine-like cytokine and functional homolog of macrophage migration inhibitory factor

D-dopachrome tautomerase (DDT), a member of the macrophage migration inhibitory factor (MIF) protein superfamily, is a newly described cytokine with chemokine-like characteristics. However, research on fish DDT remains limited. In this study, we identified a DDT homolog (LjDDT) from the Japanese sea bass, Lateolabrax japonicus. Sequence analysis showed that LjDDT had typical sequence features of known DDT and MIF homologs and was most closely related to DDT of rock bream ( Oplegnathus fasciatus). LjDDT transcripts were detected in all tested tissues of healthy Japanese sea bass, with the highest expression found in the liver. Upon infection with Vibrio harveyi, LjDDT transcripts were significantly down-regulated in the three tested tissues, including the liver, spleen, and head kidney. Recombinant LjDDT (rLjDDT) and the corresponding antibody (anti-rLjDDT) were subsequently prepared. The administration of 100 μg/g anti-rLjDDT had a statistically significant protective effect on the survival of V. harveyi-infected fish. Moreover, rLjDDT was able to induce the migration of monocytes/macrophages (MO/MФ) and lymphocytes both in vitro and in vivo, but without significant influence on the migration of neutrophils. rLjDDT exhibited chemotactic activity for lipopolysaccharide (LPS) -stimulated M1-type MO/ MΦ in vitro, but not for cAMP-stimulated M2-type MO/MΦ. Furthermore, the knockdown of LjCD74, but not LjCXCR4, significantly down-regulated the rLjDDT-enhanced migration of MO/MΦ and relieved the rLjMIF-inhibited migration of MO/MΦ. These results indicate that LjCD74 may be the major chemotactic receptor of LjDDT and LjMIF in Japanese sea bass MO/MΦ. Combined rLjDDT+ rLjMIF treatment had no significant effect on the migration of MsiRNA, LjCD74si-, or LjCXCR4sitreated MO/MΦ compared to the control group, suggesting that the roles of LjDDT and LjMIF may be antagonistic. In conclusion, our study demonstrates for the first time that DDT may play a role in the immune responses of fish against bacterial infection through chemotactic recruitment of MO/MΦ via mediation of CD74 as an antagonist of MIF.

Characterization and immunologic functions of the macrophage migration inhibitory factor from Japanese sea bass, Lateolabrax japonicus

Macrophage migration inhibitory factor (MIF) is a cytokine playing critical roles in inflammatory and immune responses. However, its functions have not been well studied in fish. In this study, we identified a MIF molecule from Japanese sea bass (Lateolabrax japonicus; LjMIF). Multiple sequence alignment showed that LjMIF has the typical structural features of MIFs. Phylogenetic tree analysis revealed that LjMIF is most closely related to the yellowfin tuna (Thunnus albacares), large yellow croaker (Larimichthys crocea), and red drum (Sciaenops ocellatus) homologs. Constitutive mRNA expression of LjMIF was detected in all tested tissues, with the highest level in the liver. Upon Vibro harveyi infection, LjMIF transcripts were altered in the tested tissues, including the liver, spleen, and head kidney. Subsequently, we prepared recombinant LjMIF (rLjMIF) and the corresponding antibody (anti-LjMIF). The in vitro study showed that rLjMIF inhibited the trafficking of Japanese sea bass monocytes/macrophages (MO/MΦ) and lymphocytes, but not of neutrophils, while anti-LjMIF had the opposite effect. rLjMIF also enhanced phagocytosis and intracellular killing of V. harveyi by MO/MΦ, while anti-LjMIF only inhibited phagocytosis by MO/MΦ. The in vivo study showed that rLjMIF aggravated the course of V. harveyi infection in Japanese sea bass, but anti-LjMIF increased the survival rate of the fish and decreased the bacterial burden. In conclusion, our observation revealed that LjMIF is closely involved in the immune responses of Japanese sea bass for combating V. harveyi infection.

Immunomodulatory Effects of Dietary Seaweeds in LPS Challenged Atlantic Salmon Salmo salar as Determined by Deep RNA Sequencing of the Head Kidney Transcriptome

Seaweeds may represent immuno-stimulants that could be used as health-promoting fish feed components. This study was performed to gain insights into the immunomodulatory effects of dietary seaweeds in Atlantic salmon. Specifically tested were 10% inclusion levels of Laminaria digitata (SW1) and a commercial blend of seaweeds (Oceanfeed^®) (SW2) against a fishmeal based control diet (FMC). Differences between groups were assessed in growth, feed conversion ratio and blood parameters hematocrit and hemoglobin. After a LPS challenge of fish representing each of the three groups, RNAseq was performed on the head kidney as major immune organ to determine transcriptomic differences in response to the immune activation. Atlantic salmon fed with dietary seaweeds did not show major differences in performance in comparison with fishmeal fed fish. RNAseq resulted in ∼154 million reads which were mapped against a NCBI Salmo salar reference and against a de novo assembled S. salar reference for analyses of expression of immune genes and ontology of immune processes among the 87,600 cDNA contigs. The dietary seaweeds provoked a more efficient immune response which involved more efficient identification of the infection site, and processing and presentation of antigens. More specifically, chemotaxis and the chemokine-mediated signaling were improved and therewith the defense response to Gram-positive bacterium reduced. Specific Laminaria digitata effects included reduction of the interferon-gamma-mediated signaling. Highly upregulated and specific for this diet was the expression of major histocompatibility complex class I-related gene protein. The commercial blend of seaweeds caused more differential expression than Laminaria digitata and improved immune processes such as receptor-mediated endocytosis and cell adhesion, and increased the expression of genes involved in response to lipopolysaccharide and inflammatory response. Particularly, expression of many important immune receptors was up-regulated illustrating increased responsiveness. NF-kappa-B inhibitor alpha is an important gene that marked the difference between both seaweed diets as Laminaria digitata inhibits the expression for this cytokine while the blend of seaweeds stimulates it. It can be concluded that the inclusion of seaweeds such as Laminaria digitata can have important modulatory effects on the immune capacity of Atlantic salmon resulting in a more efficient immune response.

A Prokineticin (PK)-like cytokine from Chinese mitten crab Eriocheir sinensis promotes the production of hemocytes via reactive oxygen species

Astakine is a cytokine-like factor containing a prokineticin domain, which directly participates in hematopoiesis and blood cell differentiation. In the present study, a novel Astakine gene was identified from Chinese mitten crab Eriocheir sinensis (designated as EsAst). The full-length cDNA of EsAst was of 1163 bp, consisting of a 5' untranslated region (UTR) of 120 bp, a 3' UTR of 656 bp, and an open reading frame (ORF) of 387 bp encoding a polypeptide of 128 amino acids. There were a signal peptide and a prokineticin domain with nine conserved cysteine residues in the deduced amino acid sequence of EsAst. EsAst shared higher similarity with Astakines from Penaeus monodon and Pacifastacus leniusculus, and it was closely clustered with the Astakine from shrimp P. monodon in the phylogenetic tree. The EsAst mRNA transcript was higher expressed in hemocytes and hepatopancreas. The relative expression level of EsAst in hemocytes was continuously increased from 1.5 to 48 h after Vibro anguillarum challenge compared that in the untreated control group. After Pichia pastoris GS115 challenge, the relative expression level of EsAst in hemocytes was also up-regulated. After rEsAst injection, ROS levels in HPT cells were also increased at 12 and 24 h, and the total hemocyte counts were also significantly increased at 6, 9, 12, and 24 h post rEsAst injection. The interference of EsAst expression with dsRNA injection could delay the recovery of hemocytes production post A. hydrophila stimulation. When mitochondrial complexes I was knock down by dsRNA, ROS levels were decreased and THCs were also decreased. Recovery of hemocyte production inducing by A. hydrophila stimulation and rEsAst injection were delayed with dsEsbc1 injection. When ROS levels were increased after RNAi of Lon protease, THCs were also increased. The expression levels of five genes (EsJNK, EsSTAT, EsPI3K, EsAKT1, EsP70S6K) involved in SAPK-JNK and mTOR signaling pathways were up-regulated at 12 and 24 h in rEsAst group and EsLon dsRNA group compared with that in EGFP dsRNA group, and were similar to the trend of ROS levels. These results collectively suggested that EsAst should be a novel Astakine to promote the production of hemocytes in a ROS-dependent way in E. sinensis.

Reprint of: The non-mammalian MIF superfamily

Macrophage migration inhibitory factor (MIF) was first described as a cytokine 50 years ago, and emerged in mammals as a pleiotropic protein with pro-inflammatory, chemotactic, and growth-promoting activities. In addition, MIF has gained substantial attention as a pivotal upstream mediator of innate and adaptive immune responses and with pathologic roles in several diseases. Of less importance in mammals is an intrinsic but non-physiologic enzymatic activity that points to MIF's evolution from an ancient defense molecule. Therefore, it is not surprising that mif-like genes also have been found across a range of different organisms including bacteria, plants, protozoa, helminths, molluscs, arthropods, fish, amphibians and birds. While Genebank analysis identifying mif-like genes across species is extensive, contained herein is an overview of the non-mammalian MIF-like proteins that have been most well studied experimentally. For many of these organisms, MIF contributes to an innate defense system or plays a role in development. For parasitic organisms however, MIF appears to function as a virulence factor aiding in the establishment or persistence of infection by modulating the host immune response. Consequently, a combined targeting of both parasitic and host MIF could lead to more effective treatment strategies for parasitic diseases of socioeconomic importance.

The non-mammalian MIF superfamily

Macrophage migration inhibitory factor (MIF) was first described as a cytokine 50 years ago, and emerged in mammals as a pleiotropic protein with pro-inflammatory, chemotactic, and growth-promoting activities. In addition, MIF has gained substantial attention as a pivotal upstream mediator of innate and adaptive immune responses and with pathologic roles in several diseases. Of less importance in mammals is an intrinsic but non-physiologic enzymatic activity that points to MIF's evolution from an ancient defense molecule. Therefore, it is not surprising that mif-like genes also have been found across a range of different organisms including bacteria, plants, ‎protozoa, helminths, molluscs, arthropods, fish, amphibians and birds. While Genebank analysis identifying mif-like genes across species is extensive, contained herein is an overview of the non-mammalian MIF-like proteins that have been most well studied experimentally. For many of these organisms, MIF contributes to an innate defense system or plays a role in development. For parasitic organisms however, MIF appears to function as a virulence factor aiding in the establishment or persistence of infection by modulating the host immune response. Consequently, a combined targeting of both parasitic and host MIF could lead to more effective treatment strategies for parasitic diseases of socioeconomic importance.

Cloning, characterization, and expression of the macrophage migration inhibitory factor gene from the black tiger shrimp (Penaeus monodon)

Macrophage migration inhibitory factor (MIF) is an ancient cytokine that engages in innate immune system of vertebrates and invertebrates. In this study, the MIF gene homologue (PmMIF) was cloned from the black tiger shrimp, Penaeus monodon. The full-length cDNA sequence of PmMIF was 838 bp and contained 78 bp 5' untranslated region (UTR) and 397 bp 3' UTR, and an open reading frame (ORF) of 363 bp which coded 120 amino acids (aa). Multiple alignment analysis showed that the deduced amino acid sequence shared 98% identities with MIF from closely related species of Litopenaeus vannamei. Quantitative real-time PCR (qRT-PCR) analysis indicated that PmMIF was highly expression observed in hepatotpancreas and gills. After Vibrio harveyi challenge, PmMIF mRNA level in hepatopancreas and gills were sharply up-regulated at 6 h post-injection, and reached the maximum at 12 h. PmMIF expression level in the hepatopancreas and gills were up-regulated markedly under low (2.3%) and high (4.3%) salinity exposure, respectively. PmMIF expression level in gills increased significantly at 12 h and reached peak values (2.5- fold, 6.4-fold and 1.8-fold compared with the control) at 12 h, 48 h and 12 h after zinc, cadmium and copper exposure, respectively. In the hepatopancreas, the expression of PmMIF reached maximum levels (8.5- fold, 6.2-fold and 2.1-fold compared with the control) at 24 h, 6 h and 48 h after zinc, cadmium and copper exposure, respectively. All the results indicate that PmMIF plays an important role in responding in the innate immune system of shrimps.

The polymorphisms of a MIF gene and their association with Vibrio resistance in the clam Meretrix meretrix

Macrophage migration inhibitory factor (MIF) is an important proinflammatory cytokine that mediates both innate and adaptive immune responses. In this study, a homolog of MIF was identified in the clam Meretrix meretrix. Ten SNPs in the DNA partial sequence of MmMIF were found to be significantly associated with Vibrio resistance (P < 0.05). Distinct expression patterns of MmMIF among different haplotypes were observed after Vibrio challenge. The results showed that haplotypes did not affect MmMIF expression in the negative control group, while the expression of MmMIF in clams with Hap1 and Hap1/Hap2 was significantly lower than that with Hap2 at 24 h in the PBS-injected group but significantly higher than that with Hap2 in the Vibrio-injected group. The results also indicate that Hap1 and Hap1/Hap2 can specifically respond to mechanical stimulation while Hap2 can specifically respond to Vibrio infection. The effect of a missense mutation was detected by site-directed mutagenesis using fusion expression of the protein, which showed that the SNP g.737 (I > V) has no effect on redox activity and tautomerase activity. These studies identified a potential marker that is enriched in Vibrio-resistant clams that can be used for the genetic breeding of Meretrix meretrix.

Macrophage migration inhibitory factor (MIF) family in arthropods: Cloning and expression analysis of two MIF and one D-dopachrome tautomerase (DDT) homologues in mud crabs, Scylla paramamosain

The macrophage migration inhibitory factor (MIF) family, consisting of MIF and D-dopachrome tautomerase (DDT) in vertebrates, is evolutionarily ancient and has been found across Kingdoms including vertebrates, invertebrates, plants and bacteria. The mammalian MIF family are chemokines at the top of the inflammatory cascade in combating infections. They also possess enzymatic activities, e.g. DDT catalysis results in the production of 5,6-dihydroxyindole (DHI), a precursor of eumelanin. MIF-like genes are widely distributed, but DDT-like genes have only been described in vertebrates and a nematode. In this report, we cloned a DDT-like gene, for the first time in arthropods, and a second MIF in mud crab. The mud crab MIF family have a three exon/two intron structure as seen in vertebrates. The identification of a DDT-like gene in mud crab and other arthropods suggests that the separation of MIF and DDT preceded the divergence of protostomes and deuterostomes. The MIF family is differentially expressed in tissues of adults and during embryonic development and early life. The high level expression of the MIF family in immune tissues, such as intestine and hepatopancreas, suggests an important role in mud crab innate immunity. Mud crab DDT is highly expressed in early embryos, in megalops and crablets and this coincides with the requirement for melanisation in egg chorion tanning and cuticular hardening in arthropods, suggesting a potential novel role of DDT in melanogenesis via its tautomerase activity to produce DHI in mud crab. The clarification of the presence of both MIF and DDT in this report paves the way for further investigation of their functional roles in immunity and in melanogenesis in mud crab and other arthropods.

Characterization of MIF family proteins: MIF and DDT from rock bream, Oplegnathus fasciatus

Macrophage migration inhibitory factor (MIF) is a pleiotropic molecule playing vital roles in various signaling cascades, including cell proliferation, and activation of immune responses against infections. It is well known as a pivotal regulator of innate immunity. In this study, we have rescued and characterized two members of the MIF family, macrophage migration inhibitory factor (OfMIF) and D-Dopachrome tautomerase (OfDDT) from rock bream, Oplegnathus fasciatus. The deduced OfMIF and OfDDT protein sequences revealed the presence of the catalytic oxidoreductase (CXXC), motif. They also possessed highly conserved proline (P(2)) and lysine residues (K(33)), responsible for their isomerase and tautomerase functions. Rock bream MIF and DDT homologues shared higher identity with fish homologues and also with mammals and occupied a distinct position in the phylogenetic tree, depicting their evolutionary conservation. The spatial expression analysis revealed the highest expression of both OfMIF and OfDDT in liver, while portraying constitutive expression in other tissues. The recombinant proteins purified using the Escherichia coli system revealed potent oxidoreductase activity against insulin with both dithiothreitol and glutathione as reducing agents. Stimulation of rock bream head kidney cells with recombinant OfMIF and OfDDT proteins induced the expression of proinflammatory cytokines like tumor necrosis factor alpha (TNF-α), interleukin-8 (IL-8) and interleukin-1β (IL-1β). These results together suggest their involvement in rock bream immune defense and this study on the novel MIF family member DDT from rock bream will pave the way for further studies of this homologue in other teleosts and delineate its multiple functions.

Macrophage migration inhibitory factor of Sciaenops ocellatus regulates immune cell trafficking and is involved in pathogen-induced immune response

Macrophage migration inhibitory factor (MIF) is a multi-functional cytokine involved in immunoregulation and inflammation. In this study, we examined the expression and biological function of a MIF, SoMIF, from red drum Sciaenops ocellatus. SoMIF is composed of 115 residues and shares 85-99% overall sequence identities with the MIF of a number of teleost. SoMIF expression was detected in a wide range of tissues and upregulated by bacterial and viral infection in a time-dependent manner. In head kidney (HK) leukocytes, pathogen infection induced SoMIF expression, and the expressed SoMIF was secreted into the extracellular milieu. Recombinant SoMIF (rSoMIF) purified from Escherichia coli inhibited the migration of both HK monocytes and lymphocytes, and this inhibitory effect was abolished by the presence of anti-rSoMIF antibodies. When rSoMIF was administered into red drum, it stimulated the production of reactive oxygen species in HK monocytes both in the presence and absence of pathogen infection. In vivo infection study showed that compared to untreated fish, fish pre-treated with rSoMIF before bacterial infection exhibited significantly lower bacterial loads in blood, kidney, spleen, and liver. Taken together, these results indicate that SoMIF is a secreted protein that regulates immune cell trafficking and is involved in pathogen-induced immune response.

Macrophage migration inhibitory factor (MIF) of the protozoan parasite Eimeria influences the components of the immune system of its host, the chicken

Macrophage migration inhibitory factor (MIF) is a soluble factor produced by sensitized T lymphocytes that inhibits the random migration of macrophages. Homologues of MIF from invertebrates have been identified, making it an interesting molecule from a functional perspective. In the present study, the localization of a parasite MIF protein as well as its effect on the host was characterized. Western blot analysis shows that Eimeria MIF (EMIF) is found during all parasite developmental stages tested. Transmission electron microscopy shows that MIF is distributed throughout cytosol and nucleus of Eimeria acervulina merozoites. Immunohistochemical analysis suggests that EMIF may be released into the surrounding tissues as early as 24 h after infection, while later during oocyst formation, MIF expression is localized to areas immediately surrounding the oocysts, as well as in wall-forming bodies. The chemotaxis assay revealed an inhibitory function of EMIF on chicken monocyte migration. Quantitative real-time PCR was performed to examine the effect of EMIF on host immune system by measuring the transcripts of inflammatory mediators. An ex vivo stimulation study showed that E. acervulina MIF (EaMIF) enhanced expression of pro-inflammatory cytokines and chemokines in the presence of lipopolysaccharide (LPS). Furthermore, sequential treatment of adherent peripheral blood mononuclear cells with EaMIF, chicken MIF, and LPS in 2-h intervals led to the highest levels of interleukin (IL)-1B, chemokine CCLi3, IL-18, and interferon-gamma mRNA expression. This study shows that parasite MIF is widely expressed and may have potential effects on the immune system of the host.

A macrophage migration inhibitory factor like oxidoreductase from pearl oyster Pinctada fucata involved in innate immune responses

Macrophage migration inhibitory factor (MIF) is an important cytokine and plays a crucial role as a pivotal regulator of innate immunity. In this study, a MIF cDNA was identified and characterized from the pearl oyster Pinctada fucata (designated as PoMIF). The full-length of PoMIF was 1544 bp and consisted of a 5'-untranslated region (UTR) of 45 bp, a 3'-UTR of 1139 bp with a polyadenylation signal (AATAAA) at 12 nucleotides upstream of the poly (A) tail. The open reading frame (ORF) of PoMIF was 360 bp which encoded a polypeptide of 120 amino acids with an estimated molecular mass of 13.3 kDa and a predicted pI of 6.1. SMART analysis showed that PoMIF contained the catalytic-sites P² and K³³ for tautomerase activity, a motif C⁵⁷GSV⁶⁰ for oxidoreductase activity and a MIF family signature D⁵⁵PCGSVEVYSIGALG⁶⁹. Homology analysis revealed that the PoMIF shared 40.3-65.5% similarity and 26.9-45.0% identity to other known MIF sequences. PoMIF mRNA was constitutively expressed in seven selected tissues of healthy pearl oysters, with the highest expression level in digestive gland. Eight hours after P. fucata was injected with Vibrio alginolyticus, the expression of PoMIF mRNA was significantly up-regulated in digestive gland, gills, hemocytes and intestine. The cDNA fragment encoding mature protein of PoMIF was subcloned to expression vector pRSET and transformed into Escherichia coli BL21 (DE3). The recombinant PoMIF (rPoMIF) was expressed and purified under optimized conditions. Function analysis showed that rPoMIF had oxidoreductase activity and could utilize dithiothreitol (DTT) as reductant to reduce insulin.

Discovery of the DIGIRR gene from teleost fish: a novel Toll-IL-1 receptor family member serving as a negative regulator of IL-1 signaling

Toll-IL-1R (TIR) family members play crucial roles in a variety of defense, inflammatory, injury, and stress responses. Although they have been widely investigated in mammals, little is known about TIRs in ancient vertebrates. In this study, we report a novel double Ig IL-1R related molecule (DIGIRR) from three model fish (Tetraodon nigroviridis, Gasterosteus aculeatus, and Takifugu rubripes), adding a previously unknown homolog to the TIR family. This DIGIRR molecule contains two Ig-like domains in the extracellular region, one Arg-Tyr-mutated TIR domain in the intracellular region, and a unique subcellular distribution within the Golgi apparatus. These characteristics distinguish DIGIRR from other known family members. In vitro injection of DIGIRR into zebrafish embryos dramatically inhibited LPS-induced and IL-1β-induced NF-κB activation. Moreover, in vivo knockdown of DIGIRR by small interfering RNA significantly promoted the expression of IL-1β-stimulated proinflammatory cytokines (IL-6 and IL-1β) in DIGIRR-silenced liver and kidney tissues and in leukocytes. These results strongly suggest that DIGIRR is an important negative regulator of LPS-mediated and IL-1β-mediated signaling pathways and inflammatory responses. The Arg-Tyr-mutated site disrupted the signal transduction ability of DIGIRR TIR. Evolutionally, we propose a hypothesis that DIGIRR and single Ig IL-1R related molecule (SIGIRR) might originate from a common ancient IL-1R-like molecule that lost one (in DIGIRR) or two (in SIGIRR) extracellular Ig-like domains and intracellular Ser and Arg-Tyr amino acids. DIGIRR might be an evolutionary "transitional molecule" between IL-1R and SIGIRR, representing a shift from a potent receptor to a negative regulator. These results help define the evolutionary history of TIR family members and their associated signaling pathways and mechanisms.

A macrophage migration inhibitory factor like gene from scallop Chlamys farreri: Involvement in immune response and wound healing

Macrophage migration inhibitory factor (MIF) is an evolutionarily ancient and highly conserved cytokine with multiple functions. In the present study, a MIF-like gene was cloned from Zhikong scallop Chlamys farreri (designated as CfMIF) based on expressed sequence tag (EST) analysis and rapid amplification of cDNA ends (RACE) approach. The full-length cDNA of CfMIF was of 2296bp, consisting of a 5' untranslated region (UTR) of 60bp, a 3' UTR of 1903bp with a poly(A) tail and an open reading frame (ORF) of 333bp encoded 111 amino acid residues with a calculated molecular mass of 12.6kDa and a theoretical isoelectric point of 5.63. The deduced amino acid sequence of CfMIF shared 27-50.5% similarity with those of other known MIFs. A conserved MIF domain was identified in the deduced amino acid sequence of CfMIF, and conserved proline(2) and lysine(33) were also found to be present in CfMIF. Phylogenetic analysis revealed that CfMIF is one of MIF members. The tissue distribution and temporal expression of CfMIF in hemocytes of scallop after lipopolysaccharide (LPS), peptidoglycan (PGN) and β-glucan stimulation were detected by real-time RT-PCR. CfMIF gene was ubiquitously expressed in six selected tissues of healthy scallops, with the higher expression levels in hepatopancreas, mantle and gill. In comparison with the control group, the expression of CfMIF mRNA in hemocytes was up-regulated significantly at 6h, 24h and 48h after LPS treatment, and at all time points after PGN and glucan treatment. The cDNA fragment encoding mature peptide of CfMIF was recombined and expressed in Escherichia coli BL21 (DE3) pLysS. The recombinant protein of CfMIF (rCfMIF) promoted sheep fibroblast migration into scraped spaces in vitro. These results generated from the present study encourage us to suggest that CfMIF was a novel member of MIF family, and it was involved in immune response and wound healing by promoting fibroblast migration.

Molecular cloning and functional characterization of the avian macrophage migration inhibitory factor (MIF)

Macrophage migration inhibitory factor (MIF) is recognized as a soluble factor produced by sensitized T lymphocytes and inhibits the random migration of macrophages. Recent studies have revealed a more prominent role for MIF as a multi-functional cytokine mediating both innate and adaptive immune responses. This study describes the cloning and functional characterization of avian MIF in an effort to better understand its role in innate and adaptive immunity, and potential use in poultry health applications. The full-length avian MIF gene was amplified from stimulated chicken lymphocytes and cloned into a prokaryotic expression vector. The confirmed 115 amino acid sequence of avian MIF has 71% identity with human and murine MIF. The bacterially expressed avian recombinant MIF (rChMIF) was purified, followed by endotoxin removal, and then tested by chemotactic assay and quantitative real-time PCR (qRT-PCR). Diff-Quick staining revealed a substantial decrease in migration of macrophages in the presence of 0.01microg/ml rChMIF. qRT-PCR analysis revealed that the presence of rChMIF enhanced levels of IL-1beta and iNOS during PBMCs stimulation with LPS. Additionally, the Con A-stimulated lymphocytes showed enhanced interferon (IFN)-gamma and IL-2 transcripts in the presence of rChMIF. Interestingly, addition of rChMIF to the stimulated PBMCs, in the presence of lymphocytes, showed anti-inflammatory function of rChMIF. To our knowledge, this study represents the first report for the functional characterization of avian MIF, demonstrating the inhibition of macrophage migration, similar to mammalian MIF, and the mediation of inflammatory responses during antigenic stimulation.

Molecular and structural characterisation of a macrophage migration inhibitory factor from sea bass (Dicentrarchus labrax L.)

The macrophage migration inhibitory factor (MIF) is a cytokine produced in numerous cell types, mainly T lymphocytes and macrophages, in response to inflammatory stimuli. In this paper we report the identification of a cDNA encoding a MIF molecule from sea bass (Dicentrarchus labrax L.), its expression analysis and its 3D structure obtained by template-based modelling. The sea bass MIF cDNA consists of 609bp that translates in one reading frame to give the entire molecule containing 115 amino acids. The sequence contains three cysteine residues in conserved positions compared to human MIF and most Teleost fishes, with the exception of zebrafish and carp. The Cys(57)-Ala(58)-Leu(59)-Cys(60) motif, present inside the stretch important for JAB1-interaction and mediator of the thiol-protein oxidoreductase activity of MIF, is conserved in sea bass, together with the Pro(2) residue that is crucial for the tautomerase catalytic activity. Real-time PCR analyses revealed that MIF is constitutively expressed in all selected tissues and organs, with the highest mRNA level observed in thymus. MIF expression was induced after 4h in vitro stimulation of head kidney leukocytes with LPS and decreased after 24h. The predicted 3D model of sea bass MIF has been used to verify the presence of structural requirements for its known biological activities.

The DC-SIGN of zebrafish: insights into the existence of a CD209 homologue in a lower vertebrate and its involvement in adaptive immunity

Dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN/CD209) has become hot topic in recent studies because of its important roles in immune responses and immune escape. CD209 has been well characterized in humans and several other mammals, but little documentation exists about it in lower vertebrates. This is the first report on the identification and functional characterization of a fish DC-SIGN/CD209 molecule. The zebrafish DC-SIGN/CD209 cDNA translates into 343 aa organized into three domains structurally conserved among vertebrates. An EPN motif essential for interacting with Ca(2+) and for recognizing mannose-containing motifs has been identified. Several conserved motifs crucial for internalization and signal transduction are also present within the cytoplasmic tail. Phylogenetic analysis supports the hypothesis that CD209 family members diverged from a common ancestor. The expression of DC-SIGN/CD209 in immune-related tissues can be significantly up-regulated by exogenous Ags and IL-4. This molecule associates with various APCs, including macrophages, B lymphocytes, and a possible dendritic cell-like (CD83(+)/CD80(+)CD209(+)) population. Functionally, T cell activation, Ab (IgM) production, and bacterial vaccination-elicited immunoprotection can be dramatically inhibited by a CD209 blockade after stimulation with keyhole limpet hemocyanin (KLH) in vivo or challenged with Aeromonas hydrophila, suggesting that DC-SIGN/CD209 in zebrafish is crucial for the initiation and development of adaptive immunity. Phagocytosis analysis showed that DC-SIGN/CD209 does not participate in the uptake of KLH Ag, suggesting that other mechanisms might exist that underlie DC-SIGN/CD209 involvement. We hope that the present study will contribute to a better cross-species understanding of the evolutionary history of the DC-SIGN/CD209 family.

Molecular cloning and characterization of macrophage migration inhibitory factor from small abalone Haliotis diversicolor supertexta

The macrophage migration inhibitory factor (mif) cDNA and its genome were cloned from small abalone Haliotis diversicolor supertexta. Small abalone mif (samif) was originally identified from an expressed sequence tag (EST) fragment from a normalized cDNA library. It's 5' untranslated region (UTR) was obtained by 5' rapid amplification of cDNA end (RACE) techniques and its genomic DNA was cloned by PCR. The full-length cDNA of samif was of 535 bp, consisting of a 5'-terminal UTR of 49 bp, an open reading frame of 384 bp and a 3'-terminal UTR of 102 bp. The deduced protein was composed of 128 amino acids, with an estimated molecular mass of 14.0 kDa and a predicted pI of 6.90. The full-length samif genomic DNA comprises 3238 bp, containing three exons and two introns. Real time quantitative PCR analysis revealed that samif gene is constitutively expressed in 6 selected tissues, and its expression level in hepatopancreas is higher than that in the other tissues (p < 0.01). Samif expression level in the hepatopancreas at 24 and 48 h after Vibrio parahaemolyticus injection was upregulated significantly (p < 0.01), but there was no significant change after exposure to tributyltin (TBT) (p > 0.05).