Alcohol impairs the myeloid proliferative response to bacteremia in mice by inhibiting the stem cell antigen-1/ERK pathway

The bone marrow endothelial progenitor cell response to septic infection

Early increase in the level of endothelial progenitor cells (EPCs) in the systemic circulation occurs in patients with septic infection/sepsis. The significance and underlying mechanisms of this response remain unclear. This study investigated the bone marrow EPC response in adult mice with septic infection induced by intravenous injection (i.v.) of Escherichia coli. For in vitro experiments, sorted marrow stem/progenitor cells (SPCs) including lineage(lin)-stem cell factor receptor (c-kit)+stem cell antigen-1 (Sca-1)-, lin-c-kit+, and lin- cells were cultured with or without lipopolysaccharides (LPSs) and recombinant murine vascular endothelial growth factor (VEGF) in the absence and presence of anti-Sca-1 crosslinking antibodies. In a separate set of experiments, marrow lin-c-kit+ cells from green fluorescence protein (GFP)+ mice, i.v. challenged with heat-inactivated E. coli or saline for 24 h, were subcutaneously implanted in Matrigel plugs for 5 weeks. Marrow lin-c-kit+ cells from Sca-1 knockout (KO) mice challenged with heat-inactivated E. coli for 24 h were cultured in the Matrigel medium for 8 weeks. The marrow pool of EPCs bearing the lin-c-kit+Sca-1+VEGF receptor 2 (VEGFR2)+ (LKS VEGFR2+) and LKS CD133+VEGFR2+ surface markers expanded rapidly following septic infection, which was supported by both proliferative activation and phenotypic conversion of marrow stem/progenitor cells. Increase in marrow EPCs and their reprogramming for enhancing angiogenic activity correlated with cell-marked upregulation of Sca-1 expression. Sca-1 was coupled with Ras-related C3 botulinum toxin substrate 2 (Rac2) in signaling the marrow EPC response. Septic infection caused a substantial increase in plasma levels of IFN-γ, VEGF, G-CSF, and SDF-1. The early increase in circulating EPCs was accompanied by their active homing and incorporation into pulmonary microvasculature. These results demonstrate that the marrow EPC response is a critical component of the host defense system. Sca-1 signaling plays a pivotal role in the regulation of EPC response in mice with septic infection.

Alcohol Consumption in Rheumatoid Arthritis: A Path through the Immune System

Benefits and harms of different components of human diet have been known for hundreds of years. Alcohol is one the highest consumed, abused, and addictive substances worldwide. Consequences of alcohol abuse are increased risks for diseases of the cardiovascular system, liver, and nervous system, as well as reduced immune system function. Paradoxically, alcohol has also been a consistent protective factor against the development of autoimmune diseases such as type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, and rheumatoid arthritis (RA). Here, we focused on summarizing current findings on the effects of alcohol, as well as of its metabolites, acetaldehyde and acetate, on the immune system and RA. Heavy or moderate alcohol consumption can affect intestinal barrier integrity, as well as the microbiome, possibly contributing to RA. Additionally, systemic increase in acetate negatively affects humoral immune response, diminishing TFH cell as well as professional antigen-presenting cell (APC) function. Hence, alcohol consumption has profound effects on the efficacy of vaccinations, but also elicits protection against autoimmune diseases. The mechanism of alcohol's negative effects on the immune system is multivariate. Future studies addressing alcohol and its metabolite acetate's effect on individual components of the immune system remains crucial for our understanding and development of novel therapeutic pathways.

Acute Alcohol Intoxication Impairs Sonic Hedgehog-Gli1 Signaling and Activation of Primitive Hematopoietic Precursor Cells in the Early Stage of Host Response to Bacteremia

BACKGROUND

Activation of hematopoietic stem cells [HSCs, lineage(lin)- stem cell growth factor receptor (c-kit)+ stem cell antigen-1(Sca-1)+ , or LKS cells in mice] is critical for initiating the granulopoietic response. This study determined the effect of alcohol exposure on sonic hedgehog (SHH) signaling in the regulation of HSC activation during bacteremia.

METHODS

Acute alcohol intoxication was induced in mice by intraperitoneal (i.p.) injection of 20% alcohol (5 g alcohol/kg body weight). Control mice received i.p. saline. Thirty minutes later, mice were intravenously (i.v.) injected with Escherichia coli (E. coli, 1 to 5 × 107 CFUs/mouse) or saline.

RESULTS

SHH expression by lineage-negative bone marrow cells (BMCs) was significantly increased 24 hours after E. coli infection. Extracellular signal-regulated kinase 1/2 (ERK1/2)-specificity protein 1 (Sp1) signaling promotes SHH expression. ERK1/2 was markedly activated in BMCs 8 hours following E. coli infection. Alcohol suppressed both the activation of ERK1/2 and up-regulation of SHH expression following E. coli infection. E. coli infection up-regulated GLI family zinc finger 1 (Gli1) gene expression by BMCs and increased Gli1 protein content in LKS cells. The extent of Gli1 expression was correlated with the activity of proliferation in LKS cells. Alcohol inhibited up-regulation of Gli1 expression and activation of LKS cells in response to E. coli infection. Alcohol also interrupted the granulopoietic response to bacteremia.

CONCLUSION

These data show that alcohol disrupts SHH-Gli1 signaling and HSC activation in the early stage of the granulopoietic response, which may serve as an important mechanism underlying the impairment of immune defense against bacterial infection in host excessively consuming alcohol.

Alcohol abuse and disorder of granulopoiesis

Granulocytes are the major type of phagocytes constituting the front line of innate immune defense against bacterial infection. In adults, granulocytes are derived from hematopoietic stem cells in the bone marrow. Alcohol is the most frequently abused substance in human society. Excessive alcohol consumption injures hematopoietic tissue, impairing bone marrow production of granulocytes through disrupting homeostasis of granulopoiesis and the granulopoietic response. Because of the compromised immune defense function, alcohol abusers are susceptible to infectious diseases, particularly septic infection. Alcoholic patients with septic infection and granulocytopenia have an exceedingly high mortality rate. Treatment of serious infection in alcoholic patients with bone marrow inhibition continues to be a major challenge. Excessive alcohol consumption also causes diseases in other organ systems, particularly severe alcoholic hepatitis which is life threatening. Corticosteroids are the only therapeutic option for improving short-term survival in patients with severe alcoholic hepatitis. The existence of advanced alcoholic liver diseases and administration of corticosteroids make it more difficult to treat serious infection in alcoholic patients with the disorder of granulopoieis. This article reviews the recent development in understanding alcohol-induced disruption of marrow granulopoiesis and the granulopoietic response with the focus on progress in delineating cell signaling mechanisms underlying the alcohol-induced injury to hematopoietic tissue. Efforts in exploring effective therapy to improve patient care in this field will also be discussed.

EVI1 overexpression reprograms hematopoiesis via upregulation of Spi1 transcription

Inv(3q26) and t(3:3)(q21;q26) are specific to poor-prognosis myeloid malignancies, and result in marked overexpression of EVI1, a zinc-finger transcription factor and myeloid-specific oncoprotein. Despite extensive study, the mechanism by which EVI1 contributes to myeloid malignancy remains unclear. Here we describe a new mouse model that mimics the transcriptional effects of 3q26 rearrangement. We show that EVI1 overexpression causes global distortion of hematopoiesis, with suppression of erythropoiesis and lymphopoiesis, and marked premalignant expansion of myelopoiesis that eventually results in leukemic transformation. We show that myeloid skewing is dependent on DNA binding by EVI1, which upregulates Spi1, encoding master myeloid regulator PU.1. We show that EVI1 binds to the -14 kb upstream regulatory element (-14kbURE) at Spi1; knockdown of Spi1 dampens the myeloid skewing. Furthermore, deletion of the -14kbURE at Spi1 abrogates the effects of EVI1 on hematopoietic stem cells. These findings support a novel mechanism of leukemogenesis through EVI1 overexpression.

Sonic Hedgehog Signaling Regulates Hematopoietic Stem/Progenitor Cell Activation during the Granulopoietic Response to Systemic Bacterial Infection

Activation and reprogramming of hematopoietic stem/progenitor cells play a critical role in the granulopoietic response to bacterial infection. Our current study determined the significance of Sonic hedgehog (SHH) signaling in the regulation of hematopoietic precursor cell activity during the host defense response to systemic bacterial infection. Bacteremia was induced in male Balb/c mice via intravenous injection (i.v.) of Escherichia coli (5 × 10⁷ CFUs/mouse). Control mice received i.v. saline. SHH protein level in bone marrow cell (BMC) lysates was markedly increased at both 24 and 48 h of bacteremia. By contrast, the amount of soluble SHH ligand in marrow elutes was significantly reduced. These contrasting alterations suggested that SHH ligand release from BMCs was reduced and/or binding of soluble SHH ligand to BMCs was enhanced. At both 12 and 24 h of bacteremia, SHH mRNA expression by BMCs was significantly upregulated. This upregulation of SHH mRNA expression was followed by a marked increase in SHH protein expression in BMCs. Activation of the ERK1/2–SP1 pathway was involved in mediating the upregulation of SHH gene expression. The major cell type showing the enhancement of SHH expression in the bone marrow was lineage positive cells. Gli1 positioned downstream of the SHH receptor activation serves as a key component of the hedgehog (HH) pathway. Primitive hematopoietic precursor cells exhibited the highest level of baseline Gli1 expression, suggesting that they were active cells responding to SHH ligand stimulation. Along with the increased expression of SHH in the bone marrow, expression of Gli1 by marrow cells was significantly upregulated at both mRNA and protein levels following bacteremia. This enhancement of Gli1 expression was correlated with activation of hematopoietic stem/progenitor cell proliferation. Mice with Gli1 gene deletion showed attenuation in activation of marrow hematopoietic stem/progenitor cell proliferation and inhibition of increase in blood granulocytes following bacteremia. Our results indicate that SHH signaling is critically important in the regulation of hematopoietic stem/progenitor cell activation and reprogramming during the granulopoietic response to serious bacterial infection.

Young Bone Marrow Sca-1 Cells Rejuvenate the Aged Heart by Promoting Epithelial-to-Mesenchymal Transition

Background: To improve the regenerative capacity of aged individuals, we reconstituted bone marrow (BM) of aged mice with young Sca-1 cells, which repopulated cardiac progenitors and prevented cardiac dysfunction after a myocardial infarction (MI). However, the mechanisms involved were incompletely elucidated. This study aimed to investigate whether young, highly regenerative BM Sca-1 cells exert their cardio-protective effects on the aged heart through reactivation of the epithelial-to-mesenchymal transition (EMT) process. Methods:In vitro, BM Sca-1 cells were co-cultured with epicardial-derived cells (EPDCs) under hypoxia condition; mRNA and protein levels of EMT genes were measured along with cellular proliferation and migration. In vivo, BM Sca-1⁺ or Sca-1^- cells from young mice (2-3 months) were transplanted into lethally-irradiated old mice (20-22 months) to generate chimeras. In addition, Sca-1 knockout (KO) mice were reconstituted with wild type (WT) BM Sca-1⁺ cells. The effects of BM Sca-1 cell on EMT reactivation and improvement of cardiac function after MI were evaluated. Results:In vitro, BM Sca-1⁺ cells increased EPDC proliferation, migration, and EMT relative to Sca-1^- cells and these effects were inhibited by a TGF-β blocker. In vivo, more young BM Sca-1⁺ than Sca-1^- cells homed to the epicardium and induced greater host EPDC proliferation, migration, and EMT after MI. Furthermore, reconstitution of Sca-1 KO mice with WT Sca-1⁺ cells was associated with the reactivation of EMT and improved cardiac function after MI. Conclusions: Young BM Sca-1⁺ cells improved cardiac regeneration through promoting EPDC proliferation, migration and reactivation of EMT via the TGF-β signaling pathway.

Impairment of Hematopoietic Precursor Cell Activation during the Granulopoietic Response to Bacteremia in Mice with Chronic-Plus-Binge Alcohol Administration

Alcohol abuse impairs immune defense. To study the effect of chronic-plus-binge alcohol exposure on the granulopoietic response, acute alcohol intoxication (intraperitoneal injection of 5 g alcohol/kg body weight) was introduced to mice chronically fed on the Lieber-DeCarli low-fat liquid alcohol diet for 5 weeks. Bacteremia was induced by intravenous injection of Escherichia coli Bacteremia caused a remarkable increase in marrow lin^- c-kit⁺ Sca-1⁺ cells. Activation of cell proliferation supported the increase in marrow lin^- c-kit⁺ Sca-1⁺ cells. Alcohol administration inhibited this activation of lin^- c-kit⁺ Sca-1⁺ cells. The bone marrow of pair-fed control mice receiving intraperitoneal saline stored a large number of mature granulocytes expressing a high level of Gr1 (Gr1^hi cells). The proportion of Gr1^hi cells and the total number of Gr1⁺ cells were markedly reduced in the bone marrow, along with an increase in the ratio of Gr1⁺ granulocytes in peripheral white blood cells following bacteremia. E. coli infection stimulated proliferation of granulopoietic precursor cells, resulting in a marked increase in the ratio of immature Gr1^lo cells in the bone marrow. Alcohol administration itself triggered marrow release of Gr1⁺ cells, resulting in reduction of the marrow granulocyte reserve with an elevation of granulocytes in the circulation. Alcohol also impaired activation of granulopoietic precursor proliferation following bacteremia. Alcohol disrupted lipopolysaccharide (LPS)-TLR4-ERK1/2-cyclin D1 signaling and inhibited upregulation of Sca-1 and C/EBPβ expression by lineage-negative marrow cells in response to bacteremia. These results indicate that chronic-plus-binge alcohol exposure inhibits the granulopoietic response by disrupting key cell signaling for hematopoietic precursor cell activation and commitment to granulocyte lineage development.

Young Bone-Marrow Sca-1+ Stem Cells Rejuvenate the Aged Heart and Improve Function after Injury through PDGFRβ-Akt pathway

Bone marrow (BM) reconstitution with young BM cells in aged recipients restores the functionality of cardiac resident BM-derived progenitors. This study investigated the cell type primarily responsible for this effect. We reconstituted old mice with BM cells from young or old mice and found that the number of stem cell antigen 1 (Sca-1) cells homing to the heart was significantly greater in young than old chimeras. We then reconstituted old mice with young BM Sca-1⁺ or Sca-1⁻ cells. We found that Sca-1 cells repopulated the recipient BM and homed to the heart. The number of BM-derived cells in the aged myocardium co-expressing PDGFRβ was 3 times greater in Sca-1⁺ than Sca-1⁻ chimeric mice. Sca-1⁺ chimeras had more active cell proliferation in the infarcted heart and improved ventricular function after MI. The improved regeneration involved activation of the PDGFRβ/Akt/p27^Kip1 pathway. Sca-1⁺ stem cells rejuvenated cardiac tissue in aged mice. Restoration of the Sca-1⁺ subset of stem cells by BM reconstitution improved cardiac tissue regeneration after injury in aged mice.

Alteration in the concentrations of Interleukin-7 (IL-7), Interleukin-10 (IL-10) and Granulocyte Colony Stimulating Factor (G-CSF) in alcohol-dependent individuals without liver disease, during detoxification therapy

BACKGROUND

The course of Interleukin-7 (IL-7), Interleukin-10 (IL-10) and Granulocyte Colony Stimulating Factor (G-CSF) was investigated in alcohol-dependent individuals without liver disease in order to ascertain the use of these cytokines as markers for the follow-up testing and the outcome of the detoxification treatment.

METHODS

Forty-eight alcohol-dependent individuals were admitted for alcohol detoxification. Blood was obtained upon admission, two weeks later and after the completion of the detoxification period (4-5 weeks). Serum IL-7, IL-10 and G-CSF were measured with a commercially available sandwich enzyme immunoassay.

RESULTS

IL-7 concentration was steadily high from admission up to two weeks later and then showed a fall, yet still remaining significantly higher than in the control group at the end of the detoxification treatment. IL-10 concentration was significantly low on admission, presenting a linear increase during therapy and remained insignificantly low at the end. G-CSF was significantly elevated on admission and presented a linear fall ending up in almost normal values at the end of the detoxification therapy.

CONCLUSIONS

The alterations in the concentration of IL-7, IL-10 and G-CSF and their trend to normalization during the detoxification therapy are indicative of the generalized immune system disorder, caused by alcohol abuse. Further studies will help in further elucidating the pathophysiology of the immune system function in alcohol abuse, while immunological parameters might serve as biological markers and diagnostic tools for the assessment of the course and the outcome of the detoxification therapy.

Blood Leukocyte Counts and Genetic Polymorphisms of Alcohol Dehydrogenase-1B and Aldehyde Dehydrogenase-2 in Japanese Alcoholic Men

BACKGROUND

Roughly 40% of East Asians have inactive aldehyde dehydrogenase-2 (ALDH2) encoded by the ALDH2*2 allele, and 90% have highly active alcohol dehydrogenase-1B (ADH1B) encoded by the ADH1B*2 allele. Macrocytosis and macrocytic anemia in alcoholics have been associated with ADH1B and ALDH2 gene variants which increase acetaldehyde (AcH) levels.

METHODS

We investigated the relationship between ADH1B*2, ALDH2*2, and leukocyte counts of Japanese alcoholic men (N = 1,661).

RESULTS

After adjusting for age, drinking habits, smoking habits, body mass index, presence of liver cirrhosis, and serum levels of C-reactive protein, we found that total and differential leukocyte counts were lower in the presence of the ALDH2*1/*2 genotype (vs. ALDH2*1/*1 genotype). ALDH2*2/*2 carriers were not found in our study population. Leukocyte, granulocyte, and monocyte counts were also lower in the presence of ADH1B*2 (vs. ADH1B*1/*1 genotype), but the lymphocyte count was higher. The ALDH2*1/*2 genotype was associated with leukocytopenia (<4,000/μl; adjusted odds ratio [95% confidence interval] = 1.89 [1.27 to 2.80]), granulocytopenia (<2,000/μl; 1.86 [1.22 to 2.82]), monocytopenia (<250/μl; 2.22 [1.49 to 3.29]), and lymphocytopenia (<1,000/μl; 1.93 [1.32 to 2.83]). In contrast, the ADH1B*2 had the opposite effect on lymphocytopenia (0.65 [0.46 to 0.93]). Considering genotype effects under conditions of immune stimulation, we observed suppressive effects of ADH1B*2 allele on leukocytosis (≥9,000/μl; 0.69 [0.50 to 0.97]), granulocytosis (≥6,500/μl; 0.66 [0.47 to 0.93]), and monocytosis (≥750/μl; 0.56 [0.39 to 0.79]). The ADH1B*2 plus ALDH2*1/*2 combination had the greatest suppressive effects on the leukocyte, granulocyte, and monocyte counts.

CONCLUSIONS

The total and differential blood leukocyte counts of Japanese alcoholics were strongly affected by their ADH1B and ALDH2 gene variants. High AcH exposure levels probably play a critical role in the suppression of blood leukocyte counts in alcoholics.

Alcohol's Effect on Host Defense

Alcohol affects many organs, including the immune system, with even moderate amounts of alcohol influencing immune responses. Although alcohol can alter the actions of all cell populations involved in the innate and adaptive immune responses, the effect in many cases is a subclinical immunosuppression that becomes clinically relevant only after a secondary insult (e.g., bacterial or viral infection or other tissue damage). Alcohol's specific effects on the innate immune system depend on the pattern of alcohol exposure, with acute alcohol inhibiting and chronic alcohol accelerating inflammatory responses. The proinflammatory effects of chronic alcohol play a major role in the pathogenesis of alcoholic liver disease and pancreatitis, but also affect numerous other organs and tissues. In addition to promoting proinflammatory immune responses, alcohol also impairs anti-inflammatory cytokines. Chronic alcohol exposure also interferes with the normal functioning of all aspects of the adaptive immune response, including both cell-mediated and humoral responses. All of these effects enhance the susceptibility of chronic alcoholics to viral and bacterial infections and to sterile inflammation.

Production and differentiation of myeloid cells driven by proinflammatory cytokines in response to acute pneumovirus infection in mice

Respiratory virus infections are often pathogenic, driving severe inflammatory responses. Most research has focused on localized effects of virus infection and inflammation. However, infection can induce broad-reaching, systemic changes that are only beginning to be characterized. In this study, we assessed the impact of acute pneumovirus infection in C57BL/6 mice on bone marrow hematopoiesis. We hypothesized that inflammatory cytokine production in the lung upregulates myeloid cell production in response to infection. We demonstrate a dramatic increase in the percentages of circulating myeloid cells, which is associated with pronounced elevations in inflammatory cytokines in serum (IFN-γ, IL-6, CCL2), bone (TNF-α), and lung tissue (TNF-α, IFN-γ, IL-6, CCL2, CCL3, G-CSF, osteopontin). Increased hematopoietic stem/progenitor cell percentages (Lineage(-)Sca-I(+)c-kit(+)) were also detected in the bone marrow. This increase was accompanied by an increase in the proportions of committed myeloid progenitors, as determined by colony-forming unit assays. However, no functional changes in hematopoietic stem cells occurred, as assessed by competitive bone marrow reconstitution. Systemic administration of neutralizing Abs to either TNF-α or IFN-γ blocked expansion of myeloid progenitors in the bone marrow and also limited virus clearance from the lung. These findings suggest that acute inflammatory cytokines drive production and differentiation of myeloid cells in the bone marrow by inducing differentiation of committed myeloid progenitors. Our findings provide insight into the mechanisms via which innate immune responses regulate myeloid cell progenitor numbers in response to acute respiratory virus infection.

Alcohol Disrupts Human Liver Stem/Progenitor Cell Proliferation and Differentiation

OBJECTIVE

Excessive alcohol consumption injures the liver resulting in various liver diseases including liver cirrhosis. Advanced liver disease continues to be a major challenge to human health. Liver stem/progenitor cells (LSPCs) are tissue specific precursors with a distinct capacity of multi-lineage differentiation. These precursor cells may play an important role in the process of tissue injury repair and pathological transition of liver structures. At the present time, knowledge about the effect of alcohol on LSPC function during the development of alcoholic liver disease remains absent. This study was conducted to investigate changes in LSPC activity of proliferation and differentiation following alcohol exposure. The disruption of cell signaling mechanisms underlying alcohol-induced alteration of LSPC activities was also examined.

METHODS

Primary and immortalized human liver stem cells (HL1-1 cells and HL1-hT1 cells, respectively) were cultured in media optimized for cell proliferation and hepatocyte differentiation in the absence and presence of ethanol. Changes in cell morphology, proliferation and differentiation were determined. Functional disruption of cell signaling components following alcohol exposure was examined.

RESULTS

Ethanol exposure suppressed HL1-1 cell growth [as measured by cell 5-bromo-2-deoxyuridine (BrdU) incorporation] mediated by epidermal growth factor (EGF) or EGF plus interleukin-6 (IL-6) in an ethanol dose-dependent manner. Similarly, ethanol inhibited BrdU incorporation into HL1-hT1 cells. Cyclin D1 mRNA expression by HL1-hT1 cells was suppressed when cells were cultured with 50 and 100 mM ethanol. Ethanol exposure induced morphological change of HL1-1 cells toward a myofibroblast-like phenotype. Furthermore, ethanol down-regulated E-cadherin expression while increasing collagen I expression by HL1-1 cells. Ethanol also stimulated Snail transcriptional repressor (Snail) and α-smooth muscle actin (α-SMA) gene expression by HL1-1 cells.

CONCLUSION

These results demonstrate that the direct effect of alcohol on LSPCs is inhibiting their proliferation and promoting mesenchymal transition during their differentiation. Alcohol interrupts LSPC differentiation through interfering Snail signaling.

Neutropenia during HIV infection: adverse consequences and remedies

Neutropenia frequently occurs in patients with Human immunodeficiency virus (HIV) infection. Causes for neutropenia during HIV infection are multifactoral, including the viral toxicity to hematopoietic tissue, the use of myelotoxic agents for treatment, complication with secondary infections and malignancies, as well as the patient's association with confounding factors which impair myelopoiesis. An increased prevalence and severity of neutropenia is commonly seen in advanced stages of HIV disease. Decline of neutrophil phagocytic defense in combination with the failure of adaptive immunity renders the host highly susceptible to developing fatal secondary infections. Neutropenia and myelosuppression also restrict the use of many antimicrobial agents for treatment of infections caused by HIV and opportunistic pathogens. In recent years, HIV infection has increasingly become a chronic disease because of progress in antiretroviral therapy (ART). Prevention and treatment of severe neutropenia becomes critical for improving the survival of HIV-infected patients.

Chronic alcohol induces M2 polarization enhancing pulmonary disease caused by exposure to particulate air pollution

BACKGROUND

Chronic alcohol consumption causes persistent oxidative stress in the lung, leading to impaired alveolar macrophage (AM) function and impaired immune responses. AMs play a critical role in protecting the lung from particulate matter (PM) inhalation by removing particulates from the airway and secreting factors which mediate airway repair. We hypothesized AM dysfunction caused by chronic alcohol consumption increases the severity of injury caused by PM inhalation.

METHODS

Age- and sex-matched C57BL/6 mice were fed the Lieber-DeCarli liquid diet containing either alcohol or an isocaloric substitution (control diet) for 8 weeks. Mice from both diet groups were exposed to combustion-derived PM (CDPM) for the final 2 weeks. AM number, maturation, and polarization status were assessed by flow cytometry. Noninvasive and invasive strategies were used to assess pulmonary function and correlated with histomorphological assessments of airway structure and matrix deposition.

RESULTS

Co-exposure to alcohol and CDPM decreased AM number and maturation status (CD11c expression), while increasing markers of M2 activation (interleukin [IL]-4Rα, Ym1, Fizz1 expression, and IL-10 and transforming growth factor [TGF]-β production). Changes in AM function were accompanied by decreased airway compliance and increased elastance. Altered lung function was attributable to elevated collagen content localized to the small airways and loss of alveolar integrity. Intranasal administration of neutralizing antibody to TGF-β during the CDPM exposure period improved changes in airway compliance and elastance, while reducing collagen content caused by co-exposure.

CONCLUSIONS

Combustion-derived PM inhalation causes enhanced disease severity in the alcoholic lung by stimulating the release of latent TGF-β stores in AMs. The combinatorial effect of elevated TGF-β, M2 polarization of AMs, and increased oxidative stress impairs pulmonary function by increasing airway collagen content and compromising alveolar integrity.

Toll-like receptor 4/stem cell antigen 1 signaling promotes hematopoietic precursor cell commitment to granulocyte development during the granulopoietic response to Escherichia coli bacteremia

In response to severe bacterial infection, bone marrow hematopoietic activity shifts toward promoting granulopoiesis. The underlying cell signaling mechanisms remain obscure. To study the role of Toll-like receptor 4 (TLR4)/stem cell antigen-1 (Sca-1) signaling in this process, bacteremia was induced in mice by intravenous injection of Escherichia coli. A subgroup of animals also received intravenous 5-bromo-2-deoxyuridine (BrdU). In a separate set of experiments, bone marrow lineage-negative (lin(-)) stem cell growth factor receptor-positive (c-kit(+)) Sca-1(-) cells containing primarily common myeloid progenitors were cultured in vitro without or with E. coli lipopolysaccharide (LPS). In genotypic background control mice, bacteremia significantly upregulated Sca-1 expression by lin(-) c-kit(+) cells, as reflected by a marked increase in BrdU-negative lin(-) c-kit(+) Sca-1(+) cells in the bone marrow. In mice with the TLR4 gene deletion, this bacteremia-evoked Sca-1 response was blocked. In vitro, LPS induced a dose-dependent increase in Sca-1 expression by cultured marrow lin(-) c-kit(+) Sca-1(-) cells. LPS-induced upregulation of Sca-1 expression was regulated at the transcriptional level. Inhibition of c-Jun N-terminal kinase/stress-activated protein kinase (JNK) activity with the specific inhibitor SP600125 suppressed LPS-induced upregulation of Sca-1 expression by marrow lin(-) c-kit(+) Sca-1(-) cells. Engagement of Sca-1 with anti-Sca-1 antibodies enhanced the expression of Sfpi1 spleen focus-forming virus (SFFV) proviral integration 1 (PU.1) in marrow lin(-) c-kit(+) Sca-1(-) cells cultured with LPS. Sca-1 null mice failed to maintain the marrow pool of granulopoietic cells following bacteremia. These results demonstrate that TLR4/Sca-1 signaling plays an important role in the regulation of hematopoietic precursor cell programming and their enhancement of granulocyte lineage commitment in response to E. coli bacteremia.

Cutting edge: Type I IFN drives emergency myelopoiesis and peripheral myeloid expansion during chronic TLR7 signaling

Mice overexpressing TLR7 (TLR7.1 mice) are a model of systemic lupus erythematosus pathogenesis and exhibit peripheral myeloid expansion. We show that TLR7.1 mice have a dramatic expansion of splenic cells that derive from granulocyte/macrophage progenitors (GMP) compared with wild-type mice. In the bone marrow, TLR7.1 mice exhibited hallmarks of emergency myelopoiesis and contained a discrete population of Sca-1(+) GMP, termed emergency GMP, which are more proliferative and superior myeloid precursors than classical Sca-1(-) GMP. The emergency myelopoiesis and peripheral myeloid expansion in TLR7.1 mice was dependent on type I IFN signaling. TLR7 agonist administration to nontransgenic mice also drove type I IFN-dependent emergency myelopoiesis. TLR7.1 plasmacytoid dendritic cells were cell-intrinsically activated by TLR7 overexpression and constitutively produced type I IFN mRNA. This study shows that type I IFN can act upon myeloid progenitors to promote the development of emergency GMP, which leads to an expansion of their progeny in the periphery.

Stem cell antigen 1 protects against cardiac hypertrophy and fibrosis after pressure overload

Stem cell antigen (Sca) 1, a glycosyl phosphatidylinositol-anchored protein localized to lipid rafts, is upregulated in the heart during myocardial infarction and renovascular hypertension-induced cardiac hypertrophy. It has been suggested that Sca-1 plays an important role in myocardial infarction. To investigate the role of Sca-1 in cardiac hypertrophy, we performed aortic banding in Sca-1 cardiac-specific transgenic mice, Sca-1 knockout mice, and their wild-type littermates. Cardiac hypertrophy was evaluated by echocardiographic, hemodynamic, pathological, and molecular analyses. Sca-1 expression was upregulated and detected in cardiomyocytes after aortic banding surgery in wild-type mice. Sca-1 transgenic mice exhibited significantly attenuated cardiac hypertrophy and fibrosis and preserved cardiac function compared with wild-type mice after 4 weeks of aortic banding. Conversely, Sca-1 knockout dramatically worsened cardiac hypertrophy, fibrosis, and dysfunction after pressure overload. Furthermore, aortic banding-induced activation of Src, mitogen-activated protein kinases, and Akt was blunted by Sca-1 overexpression and enhanced by Sca-1 deficiency. Our results suggest that Sca-1 protects against cardiac hypertrophy and fibrosis via regulation of multiple pathways in cardiomyocytes.