Protective effect of mucosal administration of recombinant human macrophage colony-stimulating factor (rhM-CSF) on mucosal infection of Sendai virus in mice

Macrophage colony stimulating factor (MCSF) of Japanese flounder (Paralichthys olivaceus): Immunoregulatory property, anti-infectious function, and interaction with MCSF receptor

Macrophage colony-stimulating factor (MCSF) is an essential growth factor to control the proliferation, differentiation and survival of the macrophage lineage in vertebrates. Sequences of MCSF have been identified in multiple teleost species, however, the functional investigations of MCSF were documented in only a few species. In this study, we examined the biological activity and the immunomodulatory property of a MCSF homologue, PoMCSF, from Japanese flounder (Paralichthys olivaceus). Structural analysis showed that PoMCSF possesses conserved structural characteristics of MCSF proteins, including a signal peptide, a CSF-1 domain, and a transmembrane region closed to the C-terminal. Under normal physiological condition, PoMCSF expression distributes in all the examined tissues, the highest three tissues are blood, muscle, and head kidney. When infected by extracellular and intracellular bacterial pathogens and viral pathogen, the PoMCSF expression patterns vary with different types of microbial pathogens infection and different immune tissues. In vitro experiment showed recombinant PoMCSF promoted the activity of macrophage. In vivo experiment indicated that PoMCSF overexpression boosted the defensive ability of flounder against Edwardsiella piscicida, a severe fish pathogen that infects multiple species of economically important fish, and regulated the expression of multiple immune-related genes. To explore the relationship between PoMCSF and its receptor PoMCSFR, anti-PoMCSFR antibody was prepared and PoMCSFR knockdown was conducted. The neutralization assay showed that when PoMCSFR was neutralized by its antibody, the role of PoMCSF on host defense against E. piscicida was weakened. Knockdown of PoMCSFR impaired the phagocytic capacity of macrophages. Collectively, these findings suggest that PoMCSF plays a crucial role in the immune defense system of Japanese flounder and the effect of PoMCSF is dependent on PoMCSFR. This study provides new insights into the biological activity of MCSF and the relationship between MCSF and MCSFR in teleost.

Ability of Orally Administered IFN-α-Containing Transgenic Potato Extracts to InhibitListeria monocytogenesInfection

Type I interferons (IFN-alpha/beta) were originally thought to be antiviral cytokines, but it has recently been reported that they also play an important role in potentiating innate and adaptive immune responses. Moreover, several studies have shown that the oral administration of type I IFN ameliorates various biologic activities. Here, we studied the ability of orally administered IFN-alpha to protect mice from systemic Listeria monocytogenes infection. Daily oral administration of purified natural IFN-alpha at a concentration of 1000 international units (IU)/20 microl reduced the bacterial burden in infected organs. We also examined the protective effect of IFN-alpha expressed in transgenic potato plants. A much lower concentration of IFN-alpha (20 IU/ 20 microl) in the plant extracts was almost as protective as much higher concentrations of purified natural IFN-alpha. Our observations indicate that transgenic cytokine-expressing plants can be used prophylactically as edible pharmaceuticals to enhance systemic defense responses in humans and animals.

Effect of polysaccharide Krestin on the up-regulation of macrophage colony-stimulating factor gene expression in protecting mouse peritoneal macrophages from oxidative injury

Oxidative injury caused by oxidatively modified low density lipoprotein (Ox-LDL) plays an important role in the transformation of macrophages into foam cells and atherogenesis. Treatments to protect macrophages from oxidative injury will be effective in treating atherosclerosis. A macrophage-specific growth factor, macrophage colony-stimulating factor (M-CSF), was reported to be able to prevent the progression of atherosclerosis in Watanabe heritable hypercholesterolemic (WHHL) rabbits. A protein-bound polysaccharide, polysaccharide Krestin (PSK), was also proven to have effects in preventing atherosclerosis in our previous work. We proposed that, both M-CSF and PSK could protect macrophages from oxidative injury, and the effects of PSK were associated with its capability of inducing M-CSF expression. In our present results, M-CSF could alleviate the Ox-LDL- or tert-butyl hydroperoxide (tbOOH)-induced injury to mouse peritoneal macrophages, and PSK exhibited some similar effects. PSK treatment could induce M-CSF gene expression and secretion in mouse peritoneal macrophages. Furthermore actinomycin D and cycloheximide could attenuate that induction. We concluded that, maybe PSK exerted its effects on macrophages partly through the transcriptional induction of M-CSF in the cells.

Expression of biologically active human tumor necrosis factor-alpha in transgenic potato plant

We report the successful insertion of the cDNA of human tumor necrosis factor-alpha (HuTNF-alpha) into the genome of potato plant species, Solanum tuberosum, using Agrobacterium tumefacience-mediated transformation. HuTNF-alpha is a known and essential cytokine mediating host defense against tumors and infectious diseases and an immunomodulating agent. To enhance the accumulation of foreign gene product expression in plant cells, the molecular design of the constructed HuTNF-alpha is presented. Transcription and translation of TNF-alpha in transformants were confirmed by Northern blot, RT-PCR, ELISA, and Western blot, respectively. Expression of the bioactive HuTNF-alpha in plant cells was confirmed by way of the cytotoxic effect of the extract obtained from the transformants against murine L929 cells. We think that the expression level of HuTNF-alpha (15 microg/g potato plant tissue) obtained in the present study may be sufficient to induce responses/effects similar to those generated by TNF-alpha in human milk administered orally. We believe that the TNF-alpha expressed in edible potato plants has tremendous potential for clinical use in the areas of medicine and veterinary science. Its usefulness and applicability, therefore, need to be fully explored.

Macrophage colony-stimulating factor reduces tert-butyl hydroperoxide induced oxidative injury to monocytes/macrophages

The transformation of macrophages into foam cells is an important event in the development of atherosclerosis, and the oxidative injury caused by oxidized low density lipoprotein (Ox-LDL) plays an essential role in that process. It has been proved that macrophage colony-stimulating factor (M-CSF) could prevent the progression of atherosclerosis in Watanabe heritable hypercholesterolemic (WHHL) rabbits. We proposed that the anti-atherogenic effect of M-CSF was partly associated with its protective effect on monocyte-derived macrophages from Ox-LDL induced oxidative injury. In order to prove this, we investigated the effect of M-CSF on the oxidative injury caused by tert-butyl hydroperoxide (tbOOH) to mouse peritoneal macrophages and U937/J774 cell lines. The results showed that M-CSF could protect mouse peritoneal macrophages from oxidative injury (presented by cell morphology and cell survival rate); L929 cell-conditioned medium (L929-CM) had the same effect as M-CSF; and anti-M-CSF monoclonal antibody could mostly block the protective effect of L929-CM on macrophages. L929-CM was proved to be also able to decrease the impact of plasma membrane fluidity in U937 and J774 cells treated with tbOOH. Incubation with tbOOH caused DNA fragmentation in U937 cells. The presence of L929-CM greatly reduced the number of apoptotic U937 cells characterized by DNA fragmentation. From these results, we concluded that M-CSF could protect monocytes/macrophages from oxidative injury. It may be one of the mechanisms which explain the anti-atherogenic effect of exogenous M-CSF in WHHL rabbits.

Cloning and sequencing of cDNA encoding bovine macrophage colony-stimulating factor (bM-CSF) and expression of recombinant bM-CSF using baculovirus

The cDNAs encoding bovine macrophage colony-stimulating factors alpha and beta (M-CSF alpha and M-CSF beta) were cloned and recombinant bovine M-CSF alpha (rbM-CSF beta) in its dimeric form was expressed by using a recombinant baculovirus/insect cell system. The predicted amino acid sequence of rbM-CSF alpha and rbM-CSF beta shared 83.3 and 75.9% (alpha), 75.3 and 65.9% (beta) similarity with the sequence for human and murine M-CSFs, respectively. The biological activity of rbM-CSF beta was confirmed by the colony-forming assay using mouse bone marrow cells. SDS-PAGE under a reducing condition showed that the molecular weight of rbM-CSF beta was approximately 34 kDa. On the other hand, Western blot analysis under a non-reducing condition revealed that this rbM-CSF beta was secreted in dimeric form into the cell supernatant.