Host antibacterial defense of 6-10 Gy γ-irradiated mice subjected to lentiviral vector-based Gas5 gene therapy.

Gut bacteria-associated sepsis is a serious concern in patients with gastrointestinal acute radiation syndrome (GIARS). In our previous studies, all mice exposed to 8 Gy of whole body γ-irradiation (8 Gy GIARS-mice) died by sepsis stemming from bacterial translocation. M1Mϕ located in the bacterial translocation site (i.e., the mesenteric lymph nodes, MLNs) have been characterized as major antibacterial effector cells. However, M2bMϕ, inhibitor cells for M1Mϕ polarization, predominated in the MLNs of these mice. The reduced expression of long noncoding RNA Gas5 was associated with M2bMϕ polarization. In this study, we tried to reduce the mortality rate of 8 Gy GIARS-mice through Gas5 gene transduction using lentivirus (Gas5 lentivirus). After Gas5 lentivirus injection, Gas5 RNA was overexpressed in MLN-F4/80+ cells of 8 Gy GIARS-mice, and these cells were identified as non-M2bMϕ. All of the 8 Gy GIARS-mice injected with Gas5 lentivirus survived 30 days or more after irradiation, and bacterial translocation and subsequent sepsis were shown to be minimal in these mice. These results indicate that the antibacterial resistance of 8 Gy GIASR-mice can be restored through the modulation of M2bMϕ located in the bacterial translocation site by Gas5 transduction.

Glycyrrhizin Protects γ-Irradiated Mice from Gut Bacteria-Associated Infectious Complications by Improving miR-222-Associated Gas5 RNA Reduction in Macrophages of the Bacterial Translocation Site.

Gut bacteria-associated sepsis is a serious concern in patients with gastrointestinal acute radiation syndrome (GIARS). In our previous studies, gut bacteria-associated sepsis caused high mortality rates in mice exposed to 6-9 Gy of γ-rays. IL-12+CD38+ iNOS+ Mϕ (M1Mϕ) located in the bacterial translocation site (mesenteric lymph nodes [MLNs]) of unirradiated mice were characterized as host defense antibacterial effector cells. However, cells isolated from the MLNs of GIARS mice were mostly CCL1+IL-10+LIGHT+miR-27a+ Mϕ (M2bMϕ, inhibitor cells for the M1Mϕ polarization). Reduced long noncoding RNA Gas5 and increased miR-222 expression in MLN-Mϕ influenced by the irradiation were shown to be associated with M2bMϕ polarization. In this study, the mortality of mice exposed to 7 Gy of γ-rays (7 Gy GIARS mice) was completely controlled after the administration of glycyrrhizin (GL), a major active ingredient in licorice root (Glycyrrhiza glabra). Bacterial translocation and subsequent sepsis were minimal in 7 Gy GIARS mice treated with GL. Increased Gas5 RNA level and decreased miR-222 expression were shown in MLN-Mϕ isolated from 7 Gy GIARS mice treated with GL, and these macrophages did not display any properties of M2bMϕ. These results indicate that gut bacteria-associated sepsis in 7 Gy GIARS mice was controlled by the GL through the inhibition of M2bMϕ polarization at the bacteria translocation site. Expression of Ccl1, a gene required for M2bMϕ survival, is silenced in the MLNs of 7 Gy GIARS mice because of Gas5 RNA, which is increased in these cells after the suppression of miR-222 (a Gas5 RNA expression inhibitor) by the GL.

Survival of Mice with Gastrointestinal Acute Radiation Syndrome through Control of Bacterial Translocation.

Macrophages (Mϕ) with the M2b phenotype (Pheno2b-Mϕ) in bacterial translocation sites have been described as cells responsible for the increased susceptibility of mice with gastrointestinal acute radiation syndrome to sepsis caused by gut bacteria. In this study, we tried to reduce the mortality of mice exposed to 7-10 Gy of gamma rays by controlling Pheno2b-Mϕ polarization in bacterial translocation sites. MicroRNA-222 was induced in association with gamma irradiation. Pheno2b-Mϕ polarization was promoted and maintained in gamma-irradiated mice through the reduction of a long noncoding RNA growth arrest-specific transcript 5 (a CCL1 gene silencer) influenced by this microRNA. Therefore, the host resistance of 7-9-Gy gamma-irradiated mice to sepsis caused by bacterial translocation was improved after treatment with CCL1 antisense oligodeoxynucleotide. However, the mortality of 10-Gy gamma-irradiated mice was not alleviated by this treatment. The crypts and villi in the ileum of 10-Gy gamma-irradiated mice were severely damaged, but these were markedly improved after transplantation of intestinal lineage cells differentiated from murine embryonic stem cells. All 10-Gy gamma-irradiated mice given both of the oligodeoxynucleotide and intestinal lineage cells survived, whereas all of the same mice given either of them died. These results indicate that high mortality rates of mice irradiated with 7-10 Gy of gamma rays are reducible by depleting CCL1 in combination with the intestinal lineage cell transplantation. These findings support the novel therapeutic possibility of victims who have gastrointestinal acute radiation syndrome for the reduction of their high mortality rates.

M2b macrophage polarization accompanied with reduction of long noncoding RNA GAS5.

Macrophages (Mϕ) are highly plastic and change their functional phenotypes depending on microenvironmental signals. Recent studies have shown that microRNAs are involved in the polarization of Mϕ. In this study, we demonstrated that the phenotype of M2bMϕ [CCL1(+) IL-10(+) LIGHT(+)] switches to other phenotypes with interchangeability attained through the increased expression of growth arrest-specific 5 RNA (GAS5 RNA), a long noncoding RNA. GAS5 RNA has been described as a silencer of the CCL1 gene. Various phenotypes of Mϕ were prepared from bone marrow-derived Mϕ (BMDMϕ) after stimulation with IFNγ [M(IFNγ)/M1Mϕ], IL-4 [M(IL-4)/M2aMϕ], LPS and immobilized IgG [M(LPS + IC)/M2bMϕ], and IL-10 [M(IL-10)/M2cMϕ]. BMDMϕ cultured with medium [M(no)/quiescent Mϕ] were used as a control. As compared to Μ(no), M(IFNγ), M(IL-4) and M(IL-10), the reduced level of GAS5 RNA was shown in M(LPS + IC). CCL1 and LIGHT mRNAs (typical biomarkers of M2bMϕ) were not expressed by M(LPS + IC) transduced with a GAS5 gene using lentiviral vector. The reduction of GAS5 RNA in M(LPS + IC) was mediated by the activation of nonsense-mediated RNA decay (NMD) pathway. BMDMϕ overexpressed with GAS5 RNA after GAS5 gene transduction did not polarize to M2bMϕ even though they were stimulated with LPS and IC in combination. These results indicate that the reduction of GAS5 RNA influenced by the NMD pathway activation leads to the Mϕ polarization stimulated with LPS and IC in combination.

Lamina propria group 2 innate lymphoid cells impair the antibacterial defense of burned mice to enterococcal translocation.

Gut microbiota that invades to the defective mucosal barrier is one of the major sources of infectious complications in severely burned hosts. In this study, a role of group 2 innate lymphoid cells (ILC2) and effects of N-{4-[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]phenyl}-2-thiophenesulfonamide (SR3335) on the host antibacterial resistance against infectious complications caused by Enterococcus faecalis oral infection were investigated in burned mice. Retinoic acid receptor-related orphan receptor α (RORα) is a transcription factor required for the development of ILC2, and SR3335 is an RORα-selective inverse agonist. All of burned mice died within 6 d of E. faecalis infection (5 × 106 CFU/mouse), whereas 100% of the same mice treated with SR3335 survived. The increased ILC2 and their cytokine products (IL-5 and IL-13) were detected in the lamina propria of mice, 1-7 d after burn injury. However, the number of ILC2 did not increase in the lamina propria of burned mice treated with SR3335. The antibacterial resistance of SCID-beige (SCIDbg) mice to E. faecalis infection was impaired by the inoculation of ILC2. BALB/c, SCIDbg, and polymorphonuclear leukocyte (PMN)-depleted SCIDbg mice were shown to be resistant against E. faecalis infection. However, all Mϕ depleted SCIDbg mice died after the infection. These results indicate that host antibacterial effector Mϕ against enterococcal translocation are influenced by ILC2, increased in the bacterial translocation site of burned mice, and sepsis stemming from E. faecalis oral infection was amazingly mitigated in these mice after treatment with SR3335, an inhibitor of cellular differentiation from an ILC precursor (ILCP) to ILC2.

Short-Term Alcohol Abstinence Improves Antibacterial Defenses of Chronic Alcohol-Consuming Mice against Gut Bacteria-Associated Sepsis Caused by Enterococcus faecalis Oral Infection.

The effects of short-term alcohol abstinence on host antibacterial resistance against Enterococcus faecalis oral infection was investigated in chronic alcohol-consuming mice [mice with 0.1 g/day of 20% ethanol consumption for 12 or 16 weeks (CAC-mice)]. These mice were highly susceptible to the infection; however, after 7 days of alcohol abstinence (aaCAC-mice), their antibacterial resistances were completely restored to the normal mouse level. Normal mice inoculated with CAC-mouse hepatic macrophages were shown to be susceptible to the infection, whereas the same macrophage preparation from aaCAC-mice did not impair the antibacterial resistance of normal mice. aaCAC-mouse liver macrophages protected nonobese diabetic-severe combined immunodeficiency IL-2Rγnull mice exposed to E. faecalis, whereas those from CAC-mice did not. Monocyte-derived (MD) M2b macrophages were predominantly isolated from CAC-mouse livers, but these cells were not significantly isolated from aaCAC-mouse livers. Hepatic MD macrophages from aaCAC-mice switched to M1 macrophages in response to bacterial antigen, whereas the same macrophage preparation from CAC-mice did not. M1 Kupffer cells, M2a Kupffer cells, and MD M2b macrophages were shown to be not bactericidal, whereas E. faecalis was killed effectively by M1 macrophages derived from aaCAC-mouse hepatic MD macrophages. These results indicate that MD M2b macrophages predominantly distributed in the liver are responsible for the impaired resistance of CAC-mice to E. faecalis oral infection, and aaCAC-mice without MD M2b macrophages in the livers are resistant to the infection.

Host antitumor resistance improved by the macrophage polarization in a chimera model of patients with HCC.

Despite major advances in curative and palliative approaches, hepatocellular carcinoma (HCC) is still the third leading cause of cancer-related death worldwide. M1 macrophages (Mϕ) play a key role in host antitumor defenses in HCC. In our study, CD14+ cells were isolated from the peripheral blood of four groups of HCC patients (group-1, patients with stage 0 HCC; group-2, patients with stage A HCC; group-3, patients with stage B HCC; and group-4, patients with stage C HCC) and characterized phenotypically. Then, CD14+ cells from group-2 and group-3 HCC patients were induced to polarize and tested for their antitumor abilities in a chimera model of HCC patients. Human HCCs (HepG2 solid tumors) grew in a chimera model of group-3 patients (group-3 HCC chimeras) but not in a chimera model of group-2 patients (group-2 HCC chimeras). In response to HCC antigens, the majority of CD14+ cells from group-2 patients (group-2 CD14+ cells) switched to the M1 phenotype (IL-12+IL-10-iNOS+cells), whereas the majority of CD14+ cells from group-3 patients (group-3 CD14+ cells) did not switch to the M1 phenotype and continued to express M2b phenotypic properties (IL-12-IL-10+CCL1+iNOS-cells). Group-3 CD14+ cells showed M1Mϕ polarization after treatment with CCL1 antisense oligodeoxynucleotide (ODN). Therefore, our study indicates that anti-HCC defenses of group-3 HCC chimeras are improved after CCL1 antisense ODN treatment.

Macrophage polarization and MRSA infection in burned mice.

Mortality associated with Staphylococcus aureus infection remains high during the sub-acute phase of burn injury. In this study, we aimed to improve antibacterial resistance of sub-acutely burned mice through macrophage polarization. Sepsis did not develop in mice at the sub-acute phase of 5% total body surface area (TBSA) burn after being infected with methicillin-resistant S. aureus (MRSA), and M1 macrophages (interleukin (IL)-10-IL-12+ inducible nitric oxide synthase+ Mφ) were isolated from these mice. In contrast, predominantly M2b macrophages (C-C motif chemokine ligand 1 (CCL1)+IL-10+IL-12- Mφ) were isolated from mice with >15% TBSA burn, and all of these mice died after the same MRSA infection. Comparing NOD scid gamma mice inoculated with Mφ with 25% TBSA burns, all mice treated with CCL1 antisense oligodeoxynucleotide (ODN) survived after MRSA infection, whereas all untreated mice given the same infection died within 4 days. CCL1 antisense ODN has been characterized as a specific polarizer of M2bMφ. M1Mφ were isolated from MRSA-infected mice with 25% TBSA burn after treatment with CCL1 antisense ODN, and these mice were shown to be resistant against a lethal dose of MRSA infection. M1Mφ were also isolated from 25% TBSA-burned mice infected with MRSA when the ODN was administered therapeutically, and subsequent sepsis was effectively controlled in these mice. These results indicate that the M2bMφ polarizer is beneficial for controlling MRSA infection in mice at the sub-acute phase of severe burn injury.

The Polarization of M2b Monocytes in Cultures of Burn Patient Peripheral CD14+ Cells Treated with a Selected Human CCL1 Antisense Oligodeoxynucleotide.

M2b macrophages (Mφ) play a major role in the increased susceptibility of subacutely burned patients, to sepsis stemming from enterococcal translocation. Certain opportunistic infections in severely burned mice have been controlled by murine CCL1 antisense oligodeoxynucleotide (ODN), a specific polarizer of mouse M2bMφ. In the present study, we have screened CCL1 antisense ODN, which is active against human M2bMφ. Among the 20 CCL1 antisense ODNs synthesized in our laboratory, HCA-11 was shown to be the most active polarizer for human CCL1+CD163+CD14+ cells. Burn patient CCL1+CD163+CD14+ cells (3 × 105 cells/mL) switched to quiescent CCL1-CD163-CD14+ cells within 48 h in cultures supplemented with 100 µg/mL of HCA-11. After treatment with a 25 µg/chimera dose of HCA-11, the bacterial growth was not observed in various organs of patient chimeras (γNSG mice inoculated with burn patient WBCs) infected with a lethal dose of Methicillin-resistant Staphylococcus aureus. The host antibacterial defenses against certain opportunistic pathogens should be improved in severely burned patients treated with a human CCL1 antisense ODN, HCA-11.

M2b Monocytes Provoke Bacterial Pneumonia and Gut Bacteria-Associated Sepsis in Alcoholics.

Chronic alcohol consumption markedly impairs host antibacterial defense against opportunistic infections. γ-irradiated NOD-SCID IL-2Rγ(null) mice inoculated with nonalcoholic PBMCs (control PBMC chimeras) resisted Klebsiella pneumonia and gut bacteria-associated sepsis, whereas the chimeras created with alcoholic PBMCs (alcoholic PBMC chimeras) were very susceptible to these infections. M1 monocytes (IL-12(+)IL-10(-)CD163(-)CD14(+) cells), major effector cells in antibacterial innate immunity, were not induced by a bacterial Ag in alcoholic PBMC cultures, and M2b monocytes (CCL1(+)CD163(+)CD14(+) cells), which predominated in alcoholic PBMCs, were shown to be inhibitor cells on the Ag-stimulated monocyte conversion from quiescent monocytes to M1 monocytes. CCL1, which functions to maintain M2b macrophage properties, was produced by M2b monocytes isolated from alcoholic PBMCs. These M2b monocytes reverted to quiescent monocytes (IL-12(-)IL-10(-)CCL1(-)CD163(-)CD14(+) cells) in cultures supplemented with CCL1 antisense oligodeoxynucleotide, and the subsequent quiescent monocytes easily converted to M1 monocytes under bacterial Ag stimulation. Alcoholic PBMC chimeras treated with CCL1 antisense oligodeoxynucleotide were resistant against pulmonary infection by K. pneumoniae and sepsis stemming from enterococcal translocation. These results indicate that a majority of monocytes polarize to an M2b phenotype in association with alcohol abuse, and this polarization contributes to the increased susceptibility of alcoholics to gut and lung infections. Bacterial pneumonia and gut bacteria-associated sepsis, frequently seen in alcoholics, can be controlled through the polarization of macrophage phenotypes.

Orosomucoid 1 drives opportunistic infections through the polarization of monocytes to the M2b phenotype.

Orosomucoid (ORM, composed of two isoforms, ORM1 and ORM2) has been described as an inducer of M2 macrophages, which are cells that decrease host antibacterial innate immunities. However, it is unknown which phenotypes of M2 macrophages are induced by ORM. In this study, healthy donor monocytes stimulated with ORM (ORM-monocytes) were characterized phenotypically and biologically. CCL1 (a biomarker of M2b macrophages) and IL-10 were detected in monocyte cultures supplemented with ORM1; however, CCL17 (a biomarker of M2a macrophages) and CXCL13 (a biomarker of M2c macrophages) were not produced in these cultures. All of these soluble factors were not detected in the culture fluids of monocytes stimulated with ORM2. Monocytes stimulated with ORM1 were characterized as CD64(-)CD209(-)CD163(+)CCL1(+) cells. MRSA and Enterococcus faecalis infections were accelerated in chimeras (NOD/scid IL-2Rγ(null) mice reconstituted with white blood cells) after inoculation with monocytes stimulated with ORM1 or treatment with ORM1; however, the infections were greatly mitigated in both chimeras inoculated with ORM1-stimulated monocytes and treated with ORM1, after an additional treatment with an inhibitor of M2b macrophages (CCL1 antisense ODN). These results indicate that ORM1 stimulates quiescent monocytes to polarize to M2b monocytes. The regulation of M2b macrophages may be beneficial in controlling opportunistic infections in patients with a large amount of plasma ORM1.

M2b macrophage elimination and improved resistance of mice with chronic alcohol consumption to opportunistic infections.

Alcohol abuse was found to predispose persons to opportunistic infections. In this study, we tried to improve the host antibacterial resistance of chronic alcohol-consuming (CAC) mice to opportunistic infections. Bactericidal macrophages with functions to produce IL-12 and to express mRNAs for CXCL9 and inducible nitric oxide synthase (M1 macrophages) were characterized as the main effector cells in host antibacterial innate immunities against infections with opportunistic pathogens. However, CAC mice were found to be carriers of M2b macrophages [macrophages with functions to produce IL-10 and to express mRNAs for CD163, chemokine ligand (CCL)1, and LIGHT (homologous to lymphotoxin, exhibits inducible expression, competes with herpes simplex virus glycoprotein D for high-voltage electron microscopy on T cells)], which were inhibitory on macrophage conversion from resident macrophages to M1 macrophages. Under treatment with CCL1 antisense oligodeoxynucleotides, a specific inhibitor of M2b macrophages, CAC mouse macrophages reverted to resident macrophages, and M1 macrophages were induced by a bacterial antigen from macrophages of CAC mice that were previously treated with the oligodeoxynucleotides. Opportunistic infections (enterococcal translocation and Klebsiella pneumonia) in CAC mice were completely controlled by CCL1 antisense oligodeoxynucleotides. These results indicate that certain opportunistic infections in alcoholics are controllable through the modulation of M2b macrophages.

Depressed production of beta-defensins from mouse splenic dendritic cells following thermal injury and its influence on susceptibility to infection.

PURPOSE: Beta-defensins (BDs) and dendritic cells (DC) have been described as major effectors on host antimicrobial innate immunities. In the present study, the ability of DC to produce BDs was explored using DC from normal mice and full-thickness (FT)-burned mice. METHODS: DCs were isolated from spleens of mice, and 1 × 10(6) cells/ml of them were cultured with LPS or SAC. Culture fluids harvested 24 h after cultivation were assayed for BD1 and BD3 and antibacterial activity (colony-counting, Pseudomonas aeruginosa). Also, DCs were tested for BD mRNAs by RT-PCR. RESULTS: Sixty-five percent of the bacterial killing activity was shown by the culture fluids of splenic DC from normal mice, while only 15 % killing activity was shown by the culture fluids of splenic DC from FT-burned mice. X-irradiated NOD SCID IL-2rγ(null) mice inoculated with splenic DC from FT-burned mice showed increased susceptibility to P. aeruginosa infection compared to those from normal mice. Mice splenic DC expressed BD1 mRNA constitutively and expressed BD3 mRNA after stimulation. These BDs were produced by mice splenic DC. As compared with DC from normal mice, DC from FT-burned mice produced decreased amounts of BD1 and BD3 in their culture fluids. CONCLUSIONS: These results indicate that (1) DC from spleens of mice have an ability to produce BDs, and (2) the production of BDs by DC is influenced strongly by thermally injured stress. Since FT-burned mice are susceptible to P. aeruginosa infection, BDs produced by DC may play an important role on the host's antibacterial resistance.

Effect of glycyrrhizin on pseudomonal skin infections in human-mouse chimeras.

In our previous studies, peripheral blood lineage(-)CD34(+)CD31(+) cells (CD31(+) IMC) appearing in severely burned patients have been characterized as inhibitor cells for the production of ß-defensins (HBDs) by human epidermal keratinocytes (NHEK). In this study, the effect of glycyrrhizin on pseudomonal skin infections was studied in a chimera model of thermal injury. Two different chimera models were utilized. Patient chimeras were created in murine antimicrobial peptide-depleted NOD-SCID IL-2rγ(null) mice that were grafted with unburned skin tissues of severely burned patients and inoculated with the same patient peripheral blood CD31(+) IMC. Patient chimera substitutes were created in the same mice that were grafted with NHEK and inoculated with experimentally induced CD31(+) IMC. In the results, both groups of chimeras treated with glycyrrhizin resisted a 20 LD50 dose of P. aeruginosa skin infection, while all chimeras in both groups treated with saline died within 3 days of the infection. Human antimicrobial peptides were detected from the grafted site tissues of both groups of chimeras treated with glycyrrhizin, while the peptides were not detected in the same area tissues of controls. HBD-1 was produced by keratinocytes in transwell-cultures performed with CD31(+) IMC and glycyrrhizin. Also, inhibitors (IL-10 and CCL2) of HBD-1 production by keratinocytes were not detected in cultures of patient CD31(+) IMC treated with glycyrrhizin. These results indicate that sepsis stemming from pseudomonal grafted site infections in a chimera model of burn injury is controllable by glycyrrhizin. Impaired antimicrobial peptide production at the infection site of severely burned patients may be restored after treatment with glycyrrhizin.

Lineage -CD34+CD31+ cells that appear in association with severe burn injury are inhibitory on the production of antimicrobial peptides by epidermal keratinocytes.

Antimicrobial peptides are major host defense effectors against Pseudomonas aeruginosa skin infections. Due to the lack of such peptide production, severely burned hosts are greatly susceptible to P. aeruginosa burn wound infection. ß-Defensin (HBD) production by normal human epidermal keratinocytes (NHEK) was inhibited by lineage(-)CD34(+) cells isolated from peripheral blood of severely burned patients. Lineage(-)CD34(+) cells obtained from severely burned patients were characterized as CD31(+), while healthy donor lineage(-)CD34(+) cells were shown to be CD31(-) cells. Lineage(-)CD34(+)CD31(-) cells did not show any inhibitory activities on HBD-1 production by NHEK. CCL2 and IL-10 released from lineage(-)CD34(+)CD31(+) cells were shown to be inhibitory on the peptide production by NHEK, while these soluble factors were not produced by lineage(-)CD34(+)CD31(-) cells. After treatment with a mixture of mAbs for CCL2 and IL-10, the culture fluids of lineage(-)CD34(+)CD31(+) cells did not show any inhibitory activities on HBD-1 production by NHEK. Lineage(-)CD34(+)CD31(+) cells that appear in association with burn injuries play a role on the inhibition of antimicrobial peptide production by skin keratinocytes through the production of CCL2 and IL-10.

Role of M2b macrophages in the acceleration of bacterial translocation and subsequent sepsis in mice exposed to whole body [137Cs] γ-irradiation.

The influence of whole-body gamma-irradiation on the antibacterial host defense against Enterococcus faecalis translocation was investigated. Mice irradiated with or without 5 Gy [(137)Cs] gamma-rays were orally infected with 10(6) CFU/mouse E. faecalis. The pathogen was detected in the mesenteric lymph nodes (MLNs) of irradiated mice 1-4 d postinfection, whereas E. faecalis was not isolated from MLNs of normal mice. All irradiated mice died within 5 d of infection, whereas no mortality was shown in normal mice infected with the pathogen. Irradiated mice inoculated with normal mouse MLN macrophages (M) were shown to be resistant against the infection, although the same mice inoculated with irradiated mouse MLNM (I-MLNM) died postinfection. I-MLNM were identified as IL-10(+)IL-12(-)CCL1(+)LIGHT(+) M (M2bM) and were shown to be inhibitory on M conversion from resident M to IL-10(-)IL-12(+)M (M1M). M2bM were demonstrated in MLNs of mice 10-35 d after gamma-irradiation. M1M were not induced by E. faecalis Ag in cultures of I-MLNM, whereas normal mouse MLNM were converted to M1M in response to the Ag stimulation. After treatment with CCL1 antisense oligodeoxynucleotides, M2bM disappeared in MLNs of irradiated mice, and M1M were generated in MLNs of these mice following E. faecalis stimulation. These results indicate that M2bM presented in the I-MLNM populations were responsible for the impaired resistance of mice irradiated with gamma-rays to bacterial translocation and subsequent sepsis. E. faecalis translocation and subsequent sepsis may be controlled immunologically by the intervention of M2bM present in MLNs.

CCL1 released from M2b macrophages is essentially required for the maintenance of their properties.

Patients with 10-30 days postburn injury are greatly susceptible to infections. M1M (IL-10(-)IL-12(+) M) are essential cells in host antibacterial innate immunity against MRSA infections. However, these effector cells are not easily generated in hosts who are carriers of M2bM (IL-12(-)IL-10(+)CCL1(+)LIGHT(+) M). M2bM are inhibitory on M1M generation. In this study, the antibacterial resistance of mice, 10-30 days postburn injury against MRSA infection, was improved by the modulation of M2bM activities. Unburned mice inoculated with M preparations from mice, 10-30 days after burn injury, were susceptible to MRSA infection, whereas unburned mice, inoculated with M preparations from the same mice that were previously treated with CCL1 antisense ODN, were resistant to the infection. M2bM, isolated from Day 15 burn mice, lost their M2bM properties 3 days after cultivation under frequent medium changes, whereas their M2bM properties remained in the same cultures supplemented with rCCL1. In cultures, M preparations from Day 15 burn mice treated with CCL1 antisense ODN did not produce CCL1 and did convert to M1M after heat-killed MRSA stimulation. Also, Day 15 burn mice treated with the ODN became resistant against MRSA infection. These results indicate that CCL1 released from M2bM is essentially required for the maintenance of their properties. The increased susceptibility of mice, 10-30 days after burn injury to MRSA infection, may be controlled through the intervention of CCL1 production by M2bM appearing in association with severe burn injuries.

Impaired ability of burn patient neutrophils to stimulate ß-defensin production by keratinocytes.

Immunosuppressive neutrophils (PMN-II) appearing in association with burn injury have a role on the increased susceptibility of burn patients to various infections. In the present study, the role of PMN-II on the production of human ß-defensins (HBDs), important molecules on host antimicrobial innate immunities, by human keratinocytes was studied. Normal human epidermal keratinocytes (NHEKs) were cultured with neutrophils (PMNs) isolated from burn patients or healthy volunteers in dual-chamber transwells. Culture fluids harvested 24 h after cultivation were assayed for HBDs using enzyme-linked immunosorbent assay. Also, these culture fluids were assayed for their antimicrobial activities by a standard colony-counting method using Pseudomonas aeruginosa. In the results, PMNs isolated from peripheral blood of burn patients were confirmed as PMN-II, because these cells produced CC-chemokine ligand 2 (CCL2), but not interleukin (IL)-12 and CC-chemokine ligand 3 (CCL3). Culture fluids of NHEK transwell-cultured with healthy PMNs exhibited strong killing activities against P. aeruginosa (96% inhibition), however, the growth of bacteria was not dramatically inhibited by the culture fluids of NHEK transwell-cultured with burn-patient PMNs (36% inhibition). IL-12 and CCL3 containing culture fluids of healthy PMNs stimulated with the bacterial antigen or rCCL3 and rIL-12 enhanced the production of HBD2 and HBD3 by NHEK, whereas CCL2 containing culture fluids of burn-patient PMN stimulated with the antigen or rCCL2 inhibited the HBD production by NHEK. These results indicate that PMN-II appearing in association with burn injury contribute to the decreased production of HBDs in thermally injured patients.

Effect of IL-10 antisense gene therapy in severely burned mice intradermally infected with MRSA.

The effect of IL-10 antisense oligodeoxynucleotides (ODN) on the susceptibility of burned mice to intradermal (i.d.) infection of methicillin-resistant Staphylococcus aureus (MRSA) was studied. Abscesses formed and sepsis did not develop in normal mice infected i.d. with 10(8)CFU/mouse of MRSA. Similarly, sepsis caused by MRSA i.d. infection did not develop and abscesses formed in burned mice treated with IL-10 antisense ODN. However, all of the burned mice treated with scrambled ODN (control group) died by infectious complications stemming from MRSA i.d. infection, and an MRSA-abscess did not form in these mice. Macrophages (Mϕ) isolated from the infection site tissue of burned mice that were treated with IL-10 antisense ODN were identified as M1Mϕ, while Mϕ isolated from burned mice that were treated with scrambled ODN were shown to be M2Mϕ. MRSA-abscesses formed in burned mice inoculated with M1Mϕ, and these mice resisted a lethal dose of MRSA i.d. infection. However, an abscess did not form, and sepsis caused by MRSA i.d. infection developed in burned mice that were inoculated with M2Mϕ. These results indicate that severely burned mice treated with IL-10 antisense ODN are resistant against i.d. infection with MRSA. M1Mϕ appeared in the infection site tissues of severely burned mice that were treated with IL-10 antisense ODN may play a role on the abscess formation and inhibiting sepsis caused by MRSA i.d. infection.

Effect of CCL2 antisense oligodeoxynucleotides on bacterial translocation and subsequent sepsis in severely burned mice orally infected with Enterococcus faecalis.

Severely burned mice are susceptible to sepsis stemming from Enterococcus faecalis translocation due to the impaired generation of M1 macrophages (M1MΦs) in local translocation sites. In our previous studies, CCL2 has been characterized as a major effector molecule on the burn-associated generation of M2MΦs, an inhibitor cell type for resident MΦ conversion into M1MΦs. In this study, we tried to protect burned mice orally infected with E. faecalis utilizing CCL2 antisense oligodeoxynucleotides (ODNs). We show that M2MΦs in mesenteric lymph nodes (MLNs) were not demonstrated in burned mice treated with CCL2 antisense ODNs. M1MΦs were not induced by heat-killed E. faecalis from resident MΦs transwell-cultured with mesenteric lymph node macrophages (MLN-MΦs) from burned mice, while M1MΦs were induced by the same antigen from resident MΦs transwell-cultured with MΦs which were isolated from burned mice treated with CCL2 antisense ODNs. Bacterial growth in MLNs was shown in burned mice orally infected with a lethal dose of E. faecalis. However, after the same infection, sepsis did not develop in burned mice treated with CCL2 antisense ODNs. These results indicate that bacterial translocation and subsequent sepsis are controlled in burned mice orally infected with a lethal dose of E. faecalis by gene therapy utilizing CCL2 antisense ODNs.