Macrophages mediate lung inflammation in a mouse model of ischemic acute kidney injury

Serum IL-6 is increased in acute kidney injury (AKI) and inhibition of IL-6 reduces AKI-mediated lung inflammation. We hypothesized that circulating monocytes produce IL-6 and that alveolar macrophages mediate lung inflammation after AKI via chemokine (CXCL1) production. To investigate systemic and alveolar macrophages in lung injury after AKI, sham operation or 22 min of renal pedicle clamping (AKI) was performed in three experimental settings: 1) systemic macrophage depletion via diphtheria toxin (DT) injection to CD11b-DTR transgenic mice, 2) DT injection to wild-type mice, and 3) alveolar macrophage depletion via intratracheal (IT) liposome-encapsulated clodronate (LEC) administration to wild-type mice. In mice with AKI and systemic macrophage depletion (CD11b-DTR transgenic administered DT) vs. vehicle-treated AKI, blood monocytes and lung interstitial macrophages were reduced, renal function was similar, serum IL-6 was increased, lung inflammation was improved, lung CXCL1 was reduced, and lung capillary leak was increased. In wild-type mice with AKI administered DT vs. vehicle, serum IL-6 was increased. In mice with AKI and alveolar macrophage depletion (IT-LEC) vs. AKI with normal alveolar macrophage content, blood monocytes and lung interstitial macrophages were similar, alveolar macrophages were reduced, renal function was similar, lung inflammation was improved, lung CXCL1 was reduced, and lung capillary leak was increased. In conclusion, administration of DT in AKI is proinflammatory, limiting the use of the DTR-transgenic model to study systemic effects of AKI. Mice with AKI and either systemic mononuclear phagocyte depletion or alveolar macrophage depletion had reduced lung inflammation and lung CXCL1, but increased lung capillary leak; thus, mononuclear phagocytes mediate lung inflammation, but they protect against lung capillary leak after ischemic AKI. Since macrophage activation and chemokine production are key events in the development of acute lung injury (ALI), these data provide further evidence that AKI may cause ALI.     

Plasticity of Ly-6C(hi) myeloid cells in T cell regulation

CD11b(+)Ly-6C(hi) cells, including inflammatory monocytes (IMCs) and inflammatory dendritic cells (IDCs), are important in infectious, autoimmune, and tumor models. However, their role in T cell regulation is controversial. In this article, we show that T cell regulation by IMCs and IDCs is determined by their activation state and is plastic during an immune response. Nonactivated IMCs and IDCs function as APCs, but activated IMCs and IDCs suppress T cells through NO production. Suppressive IMCs are induced by IFN-γ, GM-CSF, TNF-α, and CD154 derived from activated T cells during their interaction. In experimental autoimmune encephalomyelitis, CD11b(+)Ly-6C(hi) cells in the CNS are increasingly activated from disease onset to peak and switch their function from Ag presentation to T cell suppression. Furthermore, transfer of activated IMCs or IDCs enhances T cell apoptosis in the CNS and suppresses experimental autoimmune encephalomyelitis. These data highlight the interplay between innate and adaptive immunity: immunization leads to the expansion of Ly-6C(hi) myeloid cells initially promoting T cell function. As T cells become highly activated in the target tissue, they induce activation and NO production in Ly-6C(hi) myeloid cells, which in turn suppress T cells and lead to the contraction of local immune response.     

2',4',6'-Tris(methoxymethoxy) chalcone (TMMC) attenuates the severity of cerulein-induced acute pancreatitis and associated lung injury

Acute pancreatitis (AP) is an inflammatory disease involving acinar cell injury and rapid production and release of inflammatory cytokines, which play a dominant role in local pancreatic inflammation and systemic complications. 2',4',6'-Tris (methoxymethoxy) chalcone (TMMC), a synthetic chalcone derivative, displays potent anti-inflammatory effects. Therefore, we aimed to investigate whether TMMC might affect the severity of AP and pancreatitis-associated lung injury in mice. We used the cerulein hyperstimulation model of AP. Severity of pancreatitis was determined in cerulein-injected mice by histological analysis and neutrophil sequestration. The pretreatment of mice with TMMC reduced the severity of AP and pancreatitis-associated lung injury and inhibited several biochemical parameters (activity of amylase, lipase, trypsin, trypsinogen, and myeloperoxidase and production of proinflammatory cytokines). In addition, TMMC inhibited pancreatic acinar cell death and production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 by inhibiting NF-κB and extracellular signal-regulated protein kinase 1/2 (ERK1/2) activation. Neutralizing antibodies for TNF-α, IL-1β, and IL-6 inhibited cerulein-induced cell death in isolated pancreatic acinar cells. Moreover, pharmacological blockade of NF-κB/ERK1/2 reduced acinar cell death and production of TNF-α, IL-1β, and IL-6 in isolated pancreatic acinar cells. In addition, posttreatment of mice with TMMC showed reduced severity of AP and lung injury. Our results suggest that TMMC may reduce the complications associated with pancreatitis.     

Subpopulations of mouse blood monocytes differ in maturation stage and inflammatory response

Blood monocytes are well-characterized precursors for macrophages and dendritic cells. Subsets of human monocytes with differential representation in various disease states are well known. In contrast, mouse monocyte subsets have been characterized minimally. In this study we identify three subpopulations of mouse monocytes that can be distinguished by differential expression of Ly-6C, CD43, CD11c, MBR, and CD62L. The subsets share the characteristics of extensive phagocytosis, similar expression of M-CSF receptor (CD115), and development into macrophages upon M-CSF stimulation. By eliminating blood monocytes with dichloromethylene-bisphosphonate-loaded liposomes and monitoring their repopulation, we showed a developmental relationship between the subsets. Monocytes were maximally depleted 18 h after liposome application and subsequently reappeared in the circulation. These cells were exclusively of the Ly-6C(high) subset, resembling bone marrow monocytes. Serial flow cytometric analyses of newly released Ly-6C(high) monocytes showed that Ly-6C expression on these cells was down-regulated while in circulation. Under inflammatory conditions elicited either by acute infection with Listeria monocytogenes or chronic infection with Leishmania major, there was a significant increase in immature Ly-6C(high) monocytes, resembling the inflammatory left shift of granulocytes. In addition, acute peritoneal inflammation recruited preferentially Ly-6C(med-high) monocytes. Taken together, these data identify distinct subpopulations of mouse blood monocytes that differ in maturation stage and capacity to become recruited to inflammatory sites.     

Triglyceride enhances susceptibility to TNF-α-induced cell death in THP-1 cells

Monocytes and macrophages play a major role in atherosclerosis development. Previously, we found that triglyceride (TG) promoted cell death of PMA-differentiated THP-1 macrophages. In this study, we compared the responsiveness of THP-1 monocytes and PMA-differentiated THP-1 macrophages to TNF-α-induced cell death. We found that, whereas THP-1 monocytes were TNF-α-resistant, THP-1 macrophages were sensitive to TNF-α-induced cell death. THP-1 monocytes treated with TG underwent cell death beginning at 24 h and addition of TNF-α further increased cell death. Based on these observations, we hypothesized that TG-induced differentiation of THP-1 monocytes into THP-1 macrophages, subsequently allowing sensitivity to TNF-α. To determine if TG could induce differentiation of THP-1 monocytes into THP-1 macrophages, we examined the mRNA expression levels of the macrophage-specific markers, CD11b, CD18, CD36 and CD68, by RT-PCR analysis. Our results show that expression of CD11b, CD36 and CD68 increased in TG-treated THP-1 monocytes in a dose- and time-dependent manner; furthermore, TNF-α expression was upregulated in TG-treated THP-1 monocytes. We have concluded that TG induces differentiation of THP-1 monocytes into macrophages concomitant with the production of TNF-α and increased sensitivity to TNF-α-dependent cell death.     

Regulation of monocyte functional heterogeneity by miR-146a and Relb

Monocytes serve as a central defense system against infection and injury but can also promote pathological inflammatory responses. Considering the evidence that monocytes exist in at least two subsets committed to divergent functions, we investigated whether distinct factors regulate the balance between monocyte subset responses in vivo. We identified a microRNA (miRNA), miR-146a, which is differentially regulated both in mouse (Ly-6C(hi)/Ly-6C(lo)) and human (CD14(hi)/CD14(lo)CD16(+)) monocyte subsets. The single miRNA controlled the amplitude of the Ly-6C(hi) monocyte response during inflammatory challenge whereas it did not affect Ly-6C(lo) cells. miR-146a-mediated regulation was cell-intrinsic and depended on Relb, a member of the noncanonical NF-κB/Rel family, which we identified as a direct miR-146a target. These observations not only provide mechanistic insights into the molecular events that regulate responses mediated by committed monocyte precursor populations but also identify targets for manipulating Ly-6C(hi) monocyte responses while sparing Ly-6Clo monocyte activity.     

Tumor-associated macrophages recruit CCR6+ regulatory T cells and promote the development of colorectal cancer via enhancing CCL20 production in mice

Background

Tumor-associated macrophages (TAMs) remodel the colorectal cancer (CRC) microenvironment. Yet, findings on the role of TAMs in CRC seem to be contradictory compared with other cancers. FoxP3⁺ regulatory T (Treg)-cells dominantly infiltrate CRC. However, the underlying molecular mechanism in which TAMs may contribute to the trafficking of Treg-cells to the tumor mass remains unknown.

Methodology/Principal Findings

CRC was either induced by N-methyl-N-nitrosourea (MNU) and H. pylori or established by subcutaneous injection of mouse colorectal tumor cell line (CMT93) in mice. CMT93 cells were co-cultured with primary macrophages in a transwell apparatus. Recruitment of FoxP3 green fluorescence protein positive (FoxP3^GFP+) Treg-cells was assessed using the IVIS Imaging System or immunofluorescence staining. A role for macrophages in trafficking of Treg-cells and in the development of CRC was investigated in CD11b diphtheria toxin receptor (CD11b-DTR) transgenic C57BL/6J mice in which macrophages can be selectively depleted. Treg-cells remarkably infiltrated solid tumor, and predominantly expressed the homing chemokine receptor (CCR) 6 in the induced CRC model. Both CMT93 cancer cells and macrophages produced a large amount of CCL20, the sole ligand of CCR6 in vitro and in vivo. Injection of recombinant mouse CCL20 into tumor sites promoted its development with a marked recruitment of Treg-cells in the graft CRC model. Conditional macrophage ablation decreased CCL20 levels, blocked Treg-cell recruitment and inhibited tumor growth in CD11b-DTR mice grafted with CMT93.

Conclusions/Significance

TAMs recruit CCR6⁺ Treg-cells to tumor mass and promote its development via enhancing the production of CCL20 in a CRC mouse model.     

A unique hybrid renal mononuclear phagocyte activation phenotype in murine systemic lupus erythematosus nephritis

Renal infiltration with mononuclear cells is associated with poor prognosis in systemic lupus erythematosus. A renal macrophage/dendritic cell signature is associated with the onset of nephritis in NZB/W mice, and immune-modulating therapies can reverse this signature and the associated renal damage despite ongoing immune complex deposition. In nephritic NZB/W mice, renal F4/80(hi)/CD11c(int) macrophages are located throughout the interstitium, whereas F4/80(lo)/CD11c(hi) dendritic cells accumulate in perivascular lymphoid aggregates. We show here that F4/80(hi)/CD11c(int) renal macrophages have a Gr1(lo)/Ly6C(lo)/VLA4(lo)/MHCII(hi)/CD43(lo)/CD62L(lo) phenotype different from that described for inflammatory macrophages. At nephritis onset, F4/80(hi)/CD11c(int) cells upregulate cell surface CD11b, acquire cathepsin and matrix metalloproteinase activity, and accumulate large numbers of autophagocytic vacuoles; these changes reverse after the induction of remission. Latex bead labeling of peripheral blood Gr1(lo) monocytes indicates that these are the source of F4/80(hi)/CD11c(int) macrophages. CD11c(hi)/MHCII(lo) dendritic cells are found in the kidneys only after proteinuria onset, turnover rapidly, and disappear rapidly after remission induction. Gene expression profiling of the F4/80(hi)/CD11c(int) population displays increased expression of proinflammatory, regulatory, and tissue repair/degradation-associated genes at nephritis onset that reverses with remission induction. Our findings suggest that mononuclear phagocytes with an aberrant activation profile contribute to tissue damage in lupus nephritis by mediating both local inflammation and excessive tissue remodeling.     

An intracameral injection of antigen induces in situ chemokines and cytokines required for the generation of circulating immunoregulatory monocytes

Anterior Chamber-Associated Immune Deviation (ACAID) induced by an intracameral injection of antigen generates antigen-specific regulatory splenic T cells that suppress specifically cell-mediated immunity specific for the injected antigen. Circulating F4/80(+) cells recovered from mice receiving an intracameral injection of antigen are thought to be ocular in origin and induce the development of thymic and splenic regulatory T cells. We have shown previously that after the intracameral injection of antigen there is a CCR2/CCL2-dependent infiltration of circulating F4/80(+) cells into the anterior chamber associated with the generation of circulating, ACAID-inducing F4/80(+) monocytes. Here we tested the hypothesis that the intracameral injection of antigen induces events in the anterior chamber that are associated with the induction of circulating immunoregulatory monocytes that induce the suppression of cell-mediated immunity. The intracameral injection of antigen resulted in aqueous humor (i) a time- dependent increase of CCL2 and CCL7, (ii) a transient increase in TNF-α, and (iii) an infiltration of CD11b(hi), Gr1(hi) and F4/80(+) as well as F4/80(-) and Gr1(hi) peripheral blood cells into the anterior chamber. Further characterization of these F4/80(+) cells revealed that they are Ly 6C(hi), LY6G(lo) or negative, 7/4 (LY6B)(hi), CD115(+), CD45(+), CD49B(+), and CD62 L(+). Antibody-mediated neutralization of TGF-β in situ in the anterior chamber prevented the induction of circulating, ACAID-inducing monocytes and ACAID. These cells did not increase in the irides of ACAID-refractory CCR2-/- and CCL2-/- mice that received an intracameral injection of antigen. Our results extend our suggestion that ACAID is initiated as the result of a mild proinflammatory response to intracameral injection that results in the infiltration of a CCR2(+) subset of monocytes into the anterior chamber where there is a TGF-β-dependent induction of an immunosuppressive phenotype in the infiltrated monocytes that recirculate to induce antigen-specific regulatory T cells.     

The Ly-6Chigh monocyte subpopulation transports Listeria monocytogenes into the brain during systemic infection of mice

Mononuclear phagocytes can be used by intracellular pathogens to disseminate throughout the host. In the bloodstream these cells are generically referred to as monocytes. However, blood monocytes are a heterogeneous population, and the exact identity of the leukocyte(s) relevant for microbial spreading is not known. Experiments reported in this study used Listeria monocytogenes-infected mice to establish the phenotype of parasitized blood leukocytes and to test their role in systemic dissemination of intracellular bacteria. More than 90% of the blood leukocytes that were associated with bacteria were CD11b(+) mononuclear cells. Analysis of newly described monocyte subsets showed that most infected cells belonged to the Ly-6C(high) monocyte subset and that Ly-6C(high) and Ly-6C(neg-low) monocytes harbored similar numbers of bacteria per cell. Interestingly, systemic infection with wild-type or DeltaactA mutants of L. monocytogenes, both of which escape from phagosomes and replicate intracellularly, caused expansion of the Ly-6C(high) subset. In contrast, this was not evident after infection with Deltahly mutants, which neither escape phagosomes nor replicate intracellularly. Importantly, when CD11b(+) leukocytes were isolated from the brains of lethally infected mice, 88% of these cells were identified as Ly-6C(high) monocytes. Kinetic analysis showed a significant influx of Ly-6C(high) monocytes into the brain 2 days after systemic infection. This coincided with both bacterial invasion and up-regulation of brain macrophage chemoattractant protein-1 gene expression. These data indicate that the Ly-6C(high) monocyte subset transports L. monocytogenes into the brain and establish their role as Trojan horses in vivo.     

Activation of invariant NKT cells in early phase of experimental autoimmune encephalomyelitis results in differentiation of Ly6Chi inflammatory monocyte to M2 macrophages and improved outcome

Neuropathology in multiple sclerosis is closely linked to presence of macrophages in the CNS. Both M1 (inflammatory) and M2 (alternatively activated, noninflammatory) macrophages are found in the inflamed CNS and thought to differentiate from infiltrating monocytes. It is unclear whether the balance of M1 and M2 macrophages can be altered and whether this affects disease outcome. We show in this article that Ly6C(hi) inflammatory monocytes are the early and dominant infiltrating cells in the CNS during experimental autoimmune encephalomyelitis, a model for the acute phase of multiple sclerosis. Activation of invariant NKT (iNKT) cells reduced the frequency of Ly6C(hi) monocytes and increased the proportion of M2 macrophages in the CNS with associated improvement in neurologic impairment. In contrast, iNKT-deficient mice showed higher numbers of Ly6C(hi) monocytes, reduced M2, and much more severe disease. Adoptive transfer of M2-enriched cells to iNKT-deficient mice markedly improved neurologic impairment. In vitro and in vivo experiments showed that iNKT cells promote differentiation of monocytes to M2 macrophages in an IL-4 and CD1d-dependent process. These findings indicate that infiltrating Ly6C(hi) inflammatory monocytes are early players in acute neuroinflammation and that their frequency and differentiation can be influenced by activation of iNKT cells with resultant improvement in disease outcome.     

Persistent Salmonellosis Causes Pancreatitis in a Murine Model of Infection

Pancreatitis, a known risk factor for the development of pancreatic ductal adenocarcinoma, is a serious, widespread medical condition usually caused by alcohol abuse or gallstone-mediated ductal obstruction. However, many cases of pancreatitis are of an unknown etiology. Pancreatitis has been linked to bacterial infection, but causality has yet to be established. Here, we found that persistent infection of mice with the bacterial pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) was sufficient to induce pancreatitis reminiscent of the human disease. Specifically, we found that pancreatitis induced by persistent S. Typhimurium infection was characterized by a loss of pancreatic acinar cells, acinar-to-ductal metaplasia, fibrosis and accumulation of inflammatory cells, including CD11b⁺ F4/80⁺, CD11b⁺ Ly6C^int Ly6G⁺ and CD11b⁺ Ly6C^hi Ly6G⁻ cells. Furthermore, we found that S. Typhimurium colonized and persisted in the pancreas, associated with pancreatic acinar cells in vivo, and could invade cultured pancreatic acinar cells in vitro. Thus, persistent infection of mice with S. Typhimurium may serve as a useful model for the study of pancreatitis as it relates to bacterial infection. Increased knowledge of how pathogenic bacteria can cause pancreatitis will provide a more integrated picture of the etiology of the disease and could lead to the development of new therapeutic approaches for treatment and prevention of pancreatitis and pancreatic ductal adenocarcinoma.     

The Novel Cytokine Interleukin-33 Activates Acinar Cell Proinflammatory Pathways and Induces Acute Pancreatic Inflammation in Mice

Background

Acute pancreatitis is potentially fatal but treatment options are limited as disease pathogenesis is poorly understood. IL-33, a novel IL-1 cytokine family member, plays a role in various inflammatory conditions but its role in acute pancreatitis is not well understood. Specifically, whether pancreatic acinar cells produce IL-33 when stressed or respond to IL-33 stimulation, and whether IL-33 exacerbates acute pancreatic inflammation is unknown.

Methods/Results

In duct ligation-induced acute pancreatitis in mice and rats, we found that (a) IL-33 concentration was increased in the pancreas; (b) mast cells, which secrete and also respond to IL-33, showed degranulation in the pancreas and lung; (c) plasma histamine and pancreatic substance P concentrations were increased; and (d) pancreatic and pulmonary proinflammatory cytokine concentrations were increased. In isolated mouse pancreatic acinar cells, TNF-α stimulation increased IL-33 release while IL-33 stimulation increased proinflammatory cytokine release, both involving the ERK MAP kinase pathway; the flavonoid luteolin inhibited IL-33-stimulated IL-6 and CCL2/MCP-1 release. In mice without duct ligation, exogenous IL-33 administration induced pancreatic inflammation without mast cell degranulation or jejunal inflammation; pancreatic changes included multifocal edema and perivascular infiltration by neutrophils and some macrophages. ERK MAP kinase (but not p38 or JNK) and NF-kB subunit p65 were activated in the pancreas of mice receiving exogenous IL-33, and acinar cells isolated from the pancreas of these mice showed increased spontaneous cytokine release (IL-6, CXCL2/MIP-2α). Also, IL-33 activated ERK in human pancreatic tissue.

Significance

As exogenous IL-33 does not induce jejunal inflammation in the same mice in which it induces pancreatic inflammation, we have discovered a potential role for an IL-33/acinar cell axis in the recruitment of neutrophils and macrophages and the exacerbation of acute pancreatic inflammation.

Conclusion

IL-33 is induced in acute pancreatitis, activates acinar cell proinflammatory pathways and exacerbates acute pancreatic inflammation.     

A new subset of CD103+CD8alpha+ dendritic cells in the small intestine expresses TLR3, TLR7, and TLR9 and induces Th1 response and CTL activity

CD103(+) dendritic cells (DCs) are the major conventional DC population in the intestinal lamina propria (LP). Our previous report showed that a small number of cells in the LP could be classified into four subsets based on the difference in CD11c/CD11b expression patterns: CD11c(hi)CD11b(lo) DCs, CD11c(hi)CD11b(hi) DCs, CD11c(int)CD11b(int) macrophages, and CD11c(int)CD11b(hi) eosinophils. The CD11c(hi)CD11b(hi) DCs, which are CD103(+), specifically express TLR5 and induce the differentiation of naive B cells into IgA(+) plasma cells. These DCs also mediate the differentiation of Ag-specific Th17 and Th1 cells in response to flagellin. We found that small intestine CD103(+) DCs of the LP (LPDCs) could be divided into a small subset of CD8α(+) cells and a larger subset of CD8α(-) cells. Flow cytometry analysis revealed that CD103(+)CD8α(+) and CD103(+)CD8α(-) LPDCs were equivalent to CD11c(hi)CD11b(lo) and CD11c(hi)CD11b(hi) subsets, respectively. We analyzed a novel subset of CD8α(+) LPDCs to elucidate their immunological function. CD103(+)CD8α(+) LPDCs expressed TLR3, TLR7, and TLR9 and produced IL-6 and IL-12p40, but not TNF-α, IL-10, or IL-23, following TLR ligand stimulation. CD103(+)CD8α(+) LPDCs did not express the gene encoding retinoic acid-converting enzyme Raldh2 and were not involved in T cell-independent IgA synthesis or Foxp3(+) regulatory T cell induction. Furthermore, CD103(+)CD8α(+) LPDCs induced Ag-specific IgG in serum, a Th1 response, and CTL activity in vivo. Accordingly, CD103(+)CD8α(+) LPDCs exhibit a different function from CD103(+)CD8α(-) LPDCs in active immunity. This is the first analysis, to our knowledge, of CD8α(+) DCs in the LP of the small intestine.     

TNF contributes to the immunopathology of perforin/Fas ligand double deficiency

Perforin (pfp)/Fas ligand (FasL) double-deficient mice have previously been shown to be infertile, lose weight and die prematurely due to tissue destruction caused by a significant inflammatory infiltrate of monocytes/macrophages and T cells. Herein we have compared disease progression in mice additionally deficient in the inflammatory mediator TNF. Unlike pfp/FasL double-deficient mice (TNF+/+ pfp-/- gld), mice lacking functional TNF, FasL and pfp (TNF-/- pfp-/- gld) were comparatively fertile, with the majority of mice not suffering severe pancreatitis or hysterosalphingitis in the first 5 months of life. The mean lifespan of TNF-/- pfp-/- gld mice was 217 +/- 79 days compared with 69 +/- 10 days for TNF+/+ pfp-/- gld mice and the majority of moribund TNF-/- pfp-/- gld mice appeared to die as a result of severe pancreatitis, suggesting that loss of TNF was not completely protective. At 8 weeks of age, characteristics associated with the gld phenotype, such as expansion of B220+ CD4- CD8- T cells, lymphadenopathy and hypergammaglobulinemia were comparable between TNF+/+ pfp-/- gld and TNF-/- pfp-/- gld mice, although the lymphoid organs of TNF+/+ pfp-/- gld mice contained greater numbers of B220+ CD4- CD8- T cells, macrophages and T cells. We conclude that TNF is necessary for the full manifestation of immune dysregulation caused by pfp/FasL-deficiency, in particular in the early and overwhelming tissue infiltration and destruction caused by inflammatory cells.     

Ly-6G+CCR2- myeloid cells rather than Ly-6ChighCCR2+ monocytes are required for the control of bacterial infection in the central nervous system

Myeloid cell recruitment is a characteristic feature of bacterial meningitis. However, the cellular mechanisms important for the control of Streptococcus pneumoniae infection remain largely undefined. Previous pharmacological or genetic studies broadly depleted many myeloid cell types within the meninges, which did not allow defining the function of specific myeloid subsets. Herein we show that besides CD11b(+)Ly-6G(+)CCR2(-) granulocytes, also CD11b(+)Ly-6C(high)CCR2(+) but not Ly-6C(low)CCR2(-) monocytes were recruited in high numbers to the brain as early as 12 h after bacterial challenge. Surprisingly, CD11b(+)Ly-6C(high)CCR2(+) inflammatory monocytes modulated local CXCL2 and IL-1beta production within the meninges but did not provide protection against bacterial infection. Consistent with these results, CCR2 deficiency strongly impaired monocyte recruitment to the infected brains but was redundant for disease pathogenesis. In contrast, specific depletion of polymorphonuclear granulocytes caused elevated local bacterial titer within the brains, led to an aggravated clinical course, and enhanced mortality. These findings demonstrate that Ly-6C(high)CCR2(+) inflammatory monocytes play a redundant role for the host defense during bacterial meningitis and that predominantly CD11b(+)Ly-6G(+)CCR2(-) myeloid cells are involved in the restriction of the extracellular bacteria.     

The Role of M2 Macrophages in the Progression of Chronic Kidney Disease following Acute Kidney Injury

Introduction

Acute kidney injury (AKI) is a major risk factor in the development of chronic kidney disease (CKD). However, the mechanisms linking AKI to CKD remain unclear. We examined the alteration of macrophage phenotypes during an extended recovery period following ischemia/reperfusion injury (IRI) and determine their roles in the development of fibrosis.

Methods

The left renal pedicle of mice was clamped for 40 min. To deplete monocyte/macrophage, liposome clodronate was injected or CD11b-DTR and CD11c-DTR transgenic mice were used.

Results

Throughout the phase of IRI recovery, M2-phenotype macrophages made up the predominant macrophage subset. On day 28, renal fibrosis was clearly shown with increased type IV collagen and TGF-β. The depletion of macrophages induced by the liposome clodronate injection improved renal fibrosis with a reduction of kidney IL-6, type IV collagen, and TGF-β levels. Additionally, the adoptive transfer of the M2c macrophages partially reversed the beneficial effect of macrophage depletion, whereas the adoptive transfer of the M1 macrophages did not. M2 macrophages isolated from the kidneys during the recovery phase expressed 2.5 fold higher levels of TGF-β than the M1 macrophages. The injection of the diphtheria toxin into CD11b or CD11c-DTR transgenic mice resulted in lesser depletion or no change in M2 macrophages and had little impact on renal fibrosis.

Conclusion

Although M2 macrophages are known to be indispensible for short-term recovery, they are thought to be main culprit in the development of renal fibrosis following IRI.     

The inhibitory effects of Nardostachys jatamansi on alcoholic chronic pancreatitis

Nardostachys jatamansi (NJ) belonging to the Valerianaceae family has been used as a remedy for gastrointestinal inflammatory diseases for decades. However, the potential for NJ to ameliorate alcoholic chronic pancreatitis (ACP) is unknown. The aim of this study was to examine the inhibitory effects of NJ on ACP. C57black/6 mice received ethanol injections intraperitoneally for 3 weeks against a background of cerulein-induced acute pancreatitis. During ACP, NJ was ad libitum administrated orally with water. After 3 weeks of treatment, the pancreas was harvested for histological examination. NJ treatment increased the pancreatic acinar cell survival (confirmed by amylase level testing) and reduced collagen deposition and pancreatic stellate cell (PSC) activation. In addition, NJ treatment reduced the activation but not death of PSC. In conclusion, our results suggest that NJ attenuated ACP through the inhibition of PSC activation.