Ping Zhang

Enhanced granulopoietic activity is crucial for host defense against bacterial pneumonia. Alcohol impairs this response. The underlying mechanisms remain obscure. G-CSF produced by infected lung tissue plays a key role in stimulating bone marrow granulopoiesis. This study investigated the effects of alcohol on G-CSF signaling in the regulation of marrow myeloid progenitor cell proliferation in mice with Streptococcus pneumoniae pneumonia. Chronic alcohol consumption plus acute alcohol intoxication suppressed the increase in blood granulocyte counts following intrapulmonary challenge with S. pneumoniae. This suppression was associated with a significant decrease in bone marrow granulopoietic progenitor cell proliferation. Alcohol treatment significantly enhanced STAT3 phosphorylation in bone marrow cells of animals challenged with S. pneumoniae. In vitro experiments showed that G-CSF–induced activation of STAT3–p27^Kip1 pathway in murine myeloid progenitor cell line 32D-G-CSFR cells was markedly enhanced by alcohol exposure. Alcohol dose dependently inhibited G-CSF–stimulated 32D-G-CSFR cell proliferation. This impairment of myeloid progenitor cell proliferation was not attenuated by inhibition of alcohol metabolism through either the alcohol dehydrogenase pathway or the cytochrome P450 system. These data suggest that alcohol enhances G-CSF–associated STAT3–p27^Kip1 signaling, which impairs granulopoietic progenitor cell proliferation by inducing cell cycling arrest and facilitating their terminal differentiation during the granulopoietic response to pulmonary infection.

Sepsis has continuously been a leading cause of neonatal morbidity and mortality despite current advances in chemotherapy and patient intensive care facilities. Neonates are at high risk for developing bacterial infections due to quantitative and qualitative insufficiencies of innate immunity, particularly granulocyte lineage development and response to infection. Although antibiotics remain the mainstay of treatment, adjuvant therapies enhancing immune function have shown promise in treating sepsis in neonates. This article reviews current strategies for the clinical management of neonatal sepsis and analyzes mechanisms underlying insufficiencies of neutrophil defense in neonates with emphasis on new directions for adjuvant therapy development.

Background:  Alcohol intoxication suppresses both the innate and adaptive immunities. Dendritic cells (DCs) are the major cell type bridging the innate and acquired immune responses. At the present time, the effects of alcohol on DC development in hematopoietic tissues and the functional activities of DCs are incompletely elucidated. This study investigated the impact of chronic alcohol exposure on the alteration of hematopoietic precursor cell and DC populations in the bone marrow and peripheral blood of rhesus macaques.Methods:  Rhesus macaques were administered alcohol or isocaloric sucrose daily for a period of 3 months through surgically implanted gastric catheters. Peripheral blood mononuclear cells (PBMCs) and bone marrow cells (BMCs) were isolated for flow cytometric analysis after 3 months. Monocytes were cultured with human IL‐4 (10 ng/ml) and GM‐CSF (50 ng/ml) in the absence and presence of alcohol (50 mM). On day 6 of the culture, a cocktail of stimulants including IL‐1β (18 ng), IL‐6 (1800 U), TNF‐α (18 ng), and PGE₂ (1.8 μg) were added to the designated wells for transformation of immature dendritic cells (iDCs) to mature myeloid DCs. The cells were analyzed on day 8 by flow cytometry for expression of DC costimulatory molecule expression.Results:  EtOH‐treated animals had significantly lower numbers of myeloid DCs (lineage‐HLA‐DR+CD11c+CD123−) in both the PBMCs and BMCs compared to controls (5,654 ± 1,273/10⁶ vs. 2,353 ± 660/10⁶ PBMCs and 503 ± 34 vs. 195 ± 44/10⁶ BMCs). Under culture conditions, the number of lineage‐HLA‐DR+CD83+ cells was low in control wells (0.38 ± 0.08%). Alcohol inhibited the increase in the number of lineage‐HLA‐DR+CD83+ cells in iDC wells (2.30 ± 0.79% vs. 5.73 ± 1.40%). Alcohol also inhibited the increase in the number of lineage‐HLA‐DR+CD83+ cells in mature DC wells (1.23 ± 0.15% vs. 4.13 ± 0.62%).Conclusions:  Chronic EtOH decreases the bone marrow and circulating pools of myeloid DCs. Additionally, EtOH suppresses costimulatory molecule CD83 expression during DC transformation, which may attenuate the ability of DCs to initiate T‐cell expansion.

Alcohol abuse predisposes the host to bacterial infections. In response to bacterial infection, the bone marrow hematopoietic activity shifts toward granulocyte production, which is critical for enhancing host defense. This study investigated the hematopoietic precursor cell response to bacteremia and how alcohol affects this response. Acute alcohol intoxication was induced in BALB/c mice 30 min before initiation of Escherichia coli bacteremia. Bacteremia caused a significant increase in the number of bone marrow lineage (lin⁻)-c-kit⁺Sca-1⁺ cells. Marrow lin⁻c-kit⁺Sca-1⁺ cells isolated from bacteremic mice showed an increase in CFU-granulocyte/macrophage activity compared with controls. In addition to enhanced proliferation of lin⁻c-kit⁺Sca-1⁺ cells as reflected by BrdU incorporation, phenotypic inversion of lin⁻c-kit⁺Sca-1⁺Sca-1⁻ cells primarily accounted for the rapid increase in marrow lin⁻c-kit⁺Sca-1⁺ cells following bacteremia. Bacteremia increased plasma concentration of TNF-α. Culture of marrow lin⁻c-kit⁺Sca-1⁺Sca-1⁻ cells with murine rTNF-α for 24 h caused a dose-dependent increase in conversion of these cells to lin⁻c-kit⁺Sca-1⁺ cells. Sca-1 mRNA expression by the cultured cells was also up-regulated following TNF-α stimulation. Acute alcohol intoxication inhibited the increase in the number of lin⁻c-kit⁺Sca-1⁺ cells in the bone marrow after E. coli infection. Alcohol impeded the increase in BrdU incorporation into marrow lin⁻c-kit⁺Sca-1⁺ cells in response to bacteremia. Alcohol also suppressed the plasma TNF-α response to bacteremia and inhibited TNF-α-induced phenotypic inversion of lin⁻c-kit⁺Sca-1⁺Sca-1⁻ cells in vitro. These data show that alcohol inhibits the hematopoietic precursor cell response to bacteremia, which may serve as one mechanism underlying the impaired host defense in alcohol abusers with severe bacterial infections.

During bacterial infection, the bone marrow hematopoietic activity shifts toward granulocyte production, which is critical for host defenses. Along with this enhancement of granulopoiesis, the bone marrow also increases its release of hematopoietic precursors. At the present time, little is known about the commitment of hematopoietic precursor cells, including hematopoietic stem cells and progenitors, in this response. To investigate the hematopoietic precursor cell response to bacterial infection, bacteremia was established in Balb/c mice by i.v. injection of Escherichia coli. Bacteremia caused a 10-fold increase in the number of lineage (lin)−c-kit+Sca-1+ cells in the bone marrow. This dramatic expansion of the lin−c-kit+Sca-1+ cell pool resulted from both increased mitosis of these cells and inversion from lin−c-kit+Sca-1− cell phenotype. Lipopolysaccharide, tumor necrosis factor-α, and interleukin-6 were potent factors capable of mediating phenotypic inversion of lin−c-kit+Sca-1− cells. Cells in the expanded lin−c-kit+Sca-1+ cell pool contained more colony-forming unit-granulocyte/macrophage. Mobilization of lin−c-kit+Sca-1+ cells into the circulation was significantly enhanced following bacteremia. These results demonstrate that the lin−c-kit+Sca-1+ cell population in the bone marrow constitutes a key component of the host defense response to bacteremia. Functional modifications of these primitive hematopoietic precursors are critical for enhancing granulocyte production following bacterial infection.Disclosure of potential conflicts of interest is found at the end of this article.

Background: Alcohol is known to inhibit the recruitment of polymorphonuclear leukocytes (PMNs) into tissue sites including the lung. During infection and inflammation, recruited neutrophils (PMNs) release S100 proteins that function to promote the recruitment of additional phagocytes.Methods and Results: This study investigated the effects of alcohol intoxication on S100 protein production in the lung in response to lipopolysaccharide (LPS). Animals were administered alcohol (5.5 g/kg) or saline 30 minutes before intratracheal challenge with LPS (100 μg/rat). Alcohol suppressed PMN recruitment into the lung following intratracheal LPS, which was associated with an inhibition of increase in S100A8 levels in both the bronchoalveolar lavage (BAL) fluid and lysates of cells recovered by BAL at 90 minutes and 4 hours post‐LPS challenge. S100A8 and S100A9 mRNA expression in cells recovered by BAL was significantly up‐regulated at both 90 minutes and 4 hours after the LPS challenge, and alcohol also suppressed this response. In addition, intratracheal LPS caused a transient increase in S100A8 mRNA expression in circulating leukocytes at 90 minutes after the challenge. Similarly, this LPS‐induced up‐regulation of S100A8 mRNA expression was inhibited in rats intoxicated with alcohol.Conclusion: These data show that alcohol inhibits the S100 protein response in the lung, which may serve as a mechanism underlying alcohol‐induced suppression of PMN recruitment into the terminal airways during pulmonary infection.