Doxorubicin metabolism moderately attributes to putative toxicity in prodigiosin/doxorubicin synergism in vitro cells.

Doxorubicin (Dox) is a widely neoplasm chemotherapeutic drug with high incidences of cardiotoxicity. Prodigiosin (PG), a red bacterial pigment from Serratia marcescens, has been demonstrated to potentiate Dox's cytotoxicity against oral squamous cell carcinoma cells through elevating Dox influx and identified as a Dox enhancer via PG-induced autophagy; however, toxicity of normal cell remains unclear. This study is conducted to evaluate putative cytotoxicity features of PG/Dox synergism in the liver, kidney, and heart cells and further elucidate whether PG augmented Dox's effect via modulating Dox metabolism in normal cells. Murine hepatocytes FL83B, cardio-myoblast h9c2, and human kidney epithelial cells HK-2 were sequentially treated with PG and Dox by measuring cell viability, cell death characteristics, oxidative stress, Dox flux, and Dox metabolism. PG could slightly significant increase Dox cytotoxicity in all tested normal cells whose toxic alteration was less than that of oral squamous carcinoma cells. The augmentation of Dox cytotoxicity might be attributed to the increase of Dox-mediated ROS accumulation that might cause slight reduction of Dox influx and reduction of Dox metabolism. It was noteworthy to notice that sustained cytotoxicity appeared in normal cells after PG and Dox were removed. Taken together, moderately metabolic reduction of Dox might be ascribed to the mechanism of increase Dox cytotoxicity in PG-induced normal cells; nevertheless, the determination of PG/Dox dose with sustained cytotoxicity in normal cells needs to be comprehensively considered.

8-chloro-adenosine activity in FLT3-ITD acute myeloid leukemia.

Nucleoside analogs represent the backbone of several distinct chemotherapy regimens for acute myeloid leukemia (AML) and combination with tyrosine kinase inhibitors has improved survival of AML patients, including those harboring the poor-risk FLT3-ITD mutation. Although these compounds are effective in killing proliferating blasts, they lack activity against quiescent leukemia stem cells (LSCs), which contributes to initial treatment refractoriness or subsequent disease relapse. The reagent 8-chloro-adenosine (8-Cl-Ado) is a ribose-containing, RNA-directed nucleoside analog that is incorporated into newly transcribed RNA rather than in DNA, causing inhibition of RNA transcription. In this report, we demonstrate antileukemic activities of 8-Cl-Ado in vitro and in vivo and provide mechanistic insight into the mode of action of 8-Cl-Ado in AML. 8-Cl-Ado markedly induced apoptosis in LSC, with negligible effects on normal stem cells. 8-Cl-Ado was particularly effective against AML cell lines and primary AML blast cells harboring the FLT3-ITD mutation. FLT3-ITD is associated with high expression of miR-155. Furthermore, we demonstrate that 8-Cl-Ado inhibits miR-155 expression levels accompanied by induction of DNA-damage and suppression of cell proliferation, through regulation of miR-155/ErbB3 binding protein 1(Ebp1)/p53/PCNA signaling. Finally, we determined that combined treatment of NSG mice engrafted with FLT3-ITD + MV4-11 AML cells with 8-Cl-Ado and the FLT3 inhibitor AC220 (quizartinib) synergistically enhanced survival, compared with that of mice treated with the individual drugs, suggesting a potentially effective approach for FLT3-ITD AML patients.

Growth factors and medium hyperglycemia induce Sox9+ ductal cell differentiation into ß cells in mice with reversal of diabetes.

We previously reported that long-term administration of a low dose of gastrin and epidermal growth factor (GE) augments ß-cell neogenesis in late-stage diabetic autoimmune mice after eliminating insulitis by induction of mixed chimerism. However, the source of ß-cell neogenesis is still unknown. SRY (sex-determining region Y)-box 9(+) (Sox9(+)) ductal cells in the adult pancreas are clonogenic and can give rise to insulin-producing ß cells in an in vitro culture. Whether Sox9(+) ductal cells in the adult pancreas can give rise to ß cells in vivo remains controversial. Here, using lineage-tracing with genetic labeling of Insulin- or Sox9-expressing cells, we show that hyperglycemia (>300 mg/dL) is required for inducing Sox9(+) ductal cell differentiation into insulin-producing ß cells, and medium hyperglycemia (300-450 mg/dL) in combination with long-term administration of low-dose GE synergistically augments differentiation and is associated with normalization of blood glucose in nonautoimmune diabetic C57BL/6 mice. Short-term administration of high-dose GE cannot augment differentiation, although it can augment preexisting ß-cell replication. These results indicate that medium hyperglycemia combined with long-term administration of low-dose GE represents one way to induce Sox9(+) ductal cell differentiation into ß cells in adult mice.

CBFß-SMMHC creates aberrant megakaryocyte-erythroid progenitors prone to leukemia initiation in mice.

Acute myeloid leukemia (AML) arises through multistep clonal evolution characterized by stepwise accumulation of successive alterations affecting the homeostasis of differentiation, proliferation, self-renewal, and survival programs. The persistence and dynamic clonal evolution of leukemia-initiating cells and preleukemic stem cells during disease progression and treatment are thought to contribute to disease relapse and poor outcome. Inv(16)(p13q22) or t(16;16)(p13.1;q22), one of the most common cytogenetic abnormalities in AML, leads to expression of a fusion protein CBFß-SMMHC (CM) known to disrupt myeloid and lymphoid differentiation. Anemia is often observed in AML but is presumed to be a secondary consequence of leukemic clonal expansion. Here, we show that CM expression induces marked deficiencies in erythroid lineage differentiation and early preleukemic expansion of a phenotypic pre-megakaryocyte/erythrocyte (Pre-Meg/E) progenitor population. Using dual-fluorescence reporter mice in lineage tracking and repopulation assays, we show that CM expression cell autonomously causes expansion of abnormal Pre-Meg/E progenitors with compromised erythroid specification and differentiation capacity. The preleukemic Pre-Meg/Es display dysregulated erythroid and megakaryocytic fate-determining factors including increased Spi-1, Gata2, and Gfi1b and reduced Zfpm1, Pf4, Vwf, and Mpl expression. Furthermore, these abnormal preleukemic Pre-Meg/Es have enhanced stress resistance and are prone to leukemia initiation upon acquiring cooperative signals. This study reveals that the leukemogenic CM fusion protein disrupts adult erythropoiesis and creates stress-resistant preleukemic Pre-Meg/E progenitors predisposed to malignant transformation. Abnormality in Meg/E or erythroid progenitors could potentially be considered an early predictive risk factor for leukemia evolution.

Exosome-mediated microenvironment dysregulation in leukemia.

The hematopoietic stem cell (HSC) niche is composed of a complex set of stromal support cells that maintain HSCs and promote normal hematopoiesis. We now know that molecular changes within the hematopoietic niche contribute to leukemia development. Leukemia cells often reorganize the hematopoietic niche to promote and support their own survival and growth. Here we will summarize recent works that decipher the normal hematopoietic niche cellular components and describe how the leukemia-transformed niche contributes to hematological malignances. Finally, we will discuss recent publications that highlight a possible role for exosomes in the leukemia-induced niche reorganization. This article is part of a Special Issue entitled: Tumor Microenvironment Regulation of Cancer Cell Survival, Metastasis, Inflammation, and Immune Surveillance edited by Peter Ruvolo and Gregg L. Semenza.

Osteoblast ablation reduces normal long-term hematopoietic stem cell self-renewal but accelerates leukemia development.

Hematopoietic stem cells (HSCs) reside in regulatory niches in the bone marrow (BM). Although HSC niches have been extensively characterized, the role of endosteal osteoblasts (OBs) in HSC regulation requires further clarification, and the role of OBs in regulating leukemic stem cells (LSCs) is not well studied. We used an OB visualization and ablation mouse model to study the role of OBs in regulating normal HSCs and chronic myelogenous leukemia (CML) LSCs. OB ablation resulted in increase in cells with a LSK Flt3(-)CD150(+)CD48(-) long-term HSC (LTHSC) phenotype but reduction of a more highly selected LSK Flt3(-)CD34(-)CD49b(-)CD229(-) LTHSC subpopulation. LTHSCs from OB-ablated mice demonstrated loss of quiescence and reduced long-term engraftment and self-renewal capacity. Ablation of OB in a transgenic CML mouse model resulted in accelerated leukemia development with reduced survival compared with control mice. The notch ligand Jagged-1 was overexpressed on CML OBs. Normal and CML LTHSCs cultured with Jagged-1 demonstrated reduced cell cycling, consistent with a possible role for loss of Jagged-1 signals in altered HSC and LSC function after OB ablation. These studies support an important role for OBs in regulating quiescence and self-renewal of LTHSCs and a previously unrecognized role in modulating leukemia development in CML.

Altered lymphopoiesis and immunodeficiency in miR-142 null mice.

MicroRNAs (miRNAs) are a class of powerful posttranscriptional regulators implicated in the control of diverse biological processes, including regulation of hematopoiesis and the immune response. To define the biological functions of miR-142, which is preferentially and abundantly expressed in immune cells, we created a mouse line with a targeted deletion of this gene. Our analysis of miR-142(-/-) mice revealed a critical role for this miRNA in the development and homeostasis of lymphocytes. Marginal zone B cells expand in the knockout spleen, whereas the number of T and B1 B cells in the periphery is reduced. Abnormal development of hematopoietic lineages in miR-142(-/-) animals is accompanied by a profound immunodeficiency, manifested by hypoimmunoglobulinemia and failure to mount a productive immune response to soluble antigens and virus. miR-142(-/-) B cells express elevated levels of B-cell-activating factor (BAFF) receptor (BAFF-R) and as a result proliferate more robustly in response to BAFF stimulation. Lowering the BAFF-R gene dose in miR-142(-/-) mice rescues the B-cell expansion defect, suggesting that BAFF-R is a bona fide miR-142 target through which it controls B-cell homeostasis. Collectively, our results uncover miR-142 as an essential regulator of lymphopoiesis, and suggest that lesions in this miRNA gene may lead to primary immunodeficiency.

CD150(-) Side Population Defines Leukemia Stem Cells in a BALB/c Mouse Model of CML and Is Depleted by Genetic Loss of SIRT1.

Leukemia stem cells (LSCs) of chronic myeloid leukemia (CML) are refractory to tyrosine kinase inhibitor treatment, persist in the residual disease, and are important source for disease recurrence. Better understanding CML LSCs will help devise new strategies to eradicate these cells. The BALB/c mouse model of CML using retroviral bone marrow transduction and transplantation is a widely used mouse model system for CML, but LSCs in this model are poorly characterized. Here, we show that lineage negative CD150(-) side population (CD150(-)SP), but not CD150(+)SP, are CML LSCs in this model, although both CD150(-)SP and CD150(+)SP cells are enriched for long-term hematopoietic stem cells in normal BALB/c mice. We previously showed that BCR-ABL transformation activates protein lysine deacetylase SIRT1 and inhibition of SIRT1 sensitizes CML stem/progenitor cells to tyrosine kinase inhibitors by acetylating and activating p53. In this study, we demonstrate that SIRT1 homozygous knockout substantially reduces CD150(-)SP CML LSCs, and compromises the maintenance of CML LSCs in the BALB/c model. We identified several molecular alterations in CD150(-)SP LSCs that included the elevated expression of cyclin-dependent kinase Cdk6 facilitating LSC activation and significantly reduced p53 expression. SIRT1 knockout suppressed Cdk6 expression and likely increases p53 protein functions through deacetylation without increasing its expression. Our results shed novel insight into CML LSCs and support a crucial role of SIRT1 in CML LSCs. Our study also provides a novel means for assessing new agents to eradicate CML LSCs.

Clonal precursor of bone, cartilage, and hematopoietic niche stromal cells.

Organs are composites of tissue types with diverse developmental origins, and they rely on distinct stem and progenitor cells to meet physiological demands for cellular production and homeostasis. How diverse stem cell activity is coordinated within organs is not well understood. Here we describe a lineage-restricted, self-renewing common skeletal progenitor (bone, cartilage, stromal progenitor; BCSP) isolated from limb bones and bone marrow tissue of fetal, neonatal, and adult mice. The BCSP clonally produces chondrocytes (cartilage-forming) and osteogenic (bone-forming) cells and at least three subsets of stromal cells that exhibit differential expression of cell surface markers, including CD105 (or endoglin), Thy1 [or CD90 (cluster of differentiation 90)], and 6C3 [ENPEP glutamyl aminopeptidase (aminopeptidase A)]. These three stromal subsets exhibit differential capacities to support hematopoietic (blood-forming) stem and progenitor cells. Although the 6C3-expressing subset demonstrates functional stem cell niche activity by maintaining primitive hematopoietic stem cell (HSC) renewal in vitro, the other stromal populations promote HSC differentiation to more committed lines of hematopoiesis, such as the B-cell lineage. Gene expression analysis and microscopic studies further reveal a microenvironment in which CD105-, Thy1-, and 6C3-expressing marrow stroma collaborate to provide cytokine signaling to HSCs and more committed hematopoietic progenitors. As a result, within the context of bone as a blood-forming organ, the BCSP plays a critical role in supporting hematopoiesis through its generation of diverse osteogenic and hematopoietic-promoting stroma, including HSC supportive 6C3(+) niche cells.

LRF-mediated Dll4 repression in erythroblasts is necessary for hematopoietic stem cell maintenance.

Hematopoietic stem cells (HSCs) are the most primitive cells in the hematopoietic system and are under tight regulation for self-renewal and differentiation. Notch signals are essential for the emergence of definitive hematopoiesis in mouse embryos and are critical regulators of lymphoid lineage fate determination. However, it remains unclear how Notch regulates the balance between HSC self-renewal and differentiation in the adult bone marrow (BM). Here we report a novel mechanism that prevents HSCs from undergoing premature lymphoid differentiation in BM. Using a series of in vivo mouse models and functional HSC assays, we show that leukemia/lymphoma related factor (LRF) is necessary for HSC maintenance by functioning as an erythroid-specific repressor of Delta-like 4 (Dll4) expression. Lrf deletion in erythroblasts promoted up-regulation of Dll4 in erythroblasts, sensitizing HSCs to T-cell instructive signals in the BM. Our study reveals novel cross-talk between HSCs and erythroblasts, and sheds a new light on the regulatory mechanisms regulating the balance between HSC self-renewal and differentiation.

Endochondral ossification is required for haematopoietic stem-cell niche formation.

Little is known about the formation of niches, local micro-environments required for stem-cell maintenance. Here we develop an in vivo assay for adult haematopoietic stem-cell (HSC) niche formation. With this assay, we identified a population of progenitor cells with surface markers CD45(-)Tie2(-)alpha(V)(+)CD105(+)Thy1.1(-) (CD105(+)Thy1(-)) that, when sorted from 15.5 days post-coitum fetal bones and transplanted under the adult mouse kidney capsule, could recruit host-derived blood vessels, produce donor-derived ectopic bones through a cartilage intermediate and generate a marrow cavity populated by host-derived long-term reconstituting HSC (LT-HSC). In contrast, CD45(-)Tie2(-)alpha(V)(+)CD105(+)Thy1(+) (CD105(+)Thy1(+)) fetal bone progenitors form bone that does not contain a marrow cavity. Suppressing expression of factors involved in endochondral ossification, such as osterix and vascular endothelial growth factor (VEGF), inhibited niche generation. CD105(+)Thy1(-) progenitor populations derived from regions of the fetal mandible or calvaria that do not undergo endochondral ossification formed only bone without marrow in our assay. Collectively, our data implicate endochondral ossification, bone formation that proceeds through a cartilage intermediate, as a requirement for adult HSC niche formation.

Regularization using Monte Carlo simulation to make optimal beamformers robust to system perturbations.

Design of optimal beamformers that withstand system perturbations such as channel mismatch, sensor position error, and pointing error has been a key issue in real-world applications of arrays. This paper aims to characterize the array performance in relation to the random perturbations from a statistical perspective. In the synthesis stage, directivity index and front-to-back ratio are employed as the performance measures for beamformer optimization. Filter coefficients of the arrays are determined using the least-squares and convex optimization approaches using the preceding performance measures. Next, Monte Carlo sampling are conducted to simulate the stochastic system perturbations following either uniform distribution or normal distribution. Statistics including the sample mean, maximum, minimum, and the maximum likelihood (ML) of the preceding performance measures are calculated. Three regularization criteria based on max-mean, max-min, and max-ML of performance measures are proposed for choosing regularization parameters used in beamformer optimization. The max-mean criterion was found most useful to determine either a simple constant or a frequency-dependent regularization parameter. To validate the proposed methods, experiments of beam patterns and automatic speech recognition test were conducted for directional and diffuse noise suppression problems, where optimal beamformers designed with the regularization parameter selected by the preceding procedures were utilized.

The chymase mouse mast cell protease 4 degrades TNF, limits inflammation, and promotes survival in a model of sepsis.

Mouse mast cell protease 4 (mMCP-4), the mouse counterpart of human mast cell chymase, is thought to have proinflammatory effects in innate or adaptive immune responses associated with mast cell activation. However, human chymase can degrade the proinflammatory cytokine TNF, a mediator that can be produced by mast cells and many other cell types. We found that mMCP-4 can reduce levels of mouse mast cell-derived TNF in vitro through degradation of transmembrane and soluble TNF. We assessed the effects of interactions between mMCP-4 and TNF in vivo by analyzing the features of a classic model of polymicrobial sepsis, cecal ligation and puncture (CLP), in C57BL/6J-mMCP-4-deficient mice versus C57BL/6J wild-type mice, and in C57BL/6J-Kit(W-sh/W-sh) mice containing adoptively transferred mast cells that were either wild type or lacked mMCP-4, TNF, or both mediators. The mMCP-4-deficient mice exhibited increased levels of intraperitoneal TNF, higher numbers of peritoneal neutrophils, and increased acute kidney injury after CLP, and also had significantly higher mortality after this procedure. Our findings support the conclusion that mMCP-4 can enhance survival after CLP at least in part by limiting detrimental effects of TNF, and suggest that mast cell chymase may represent an important negative regulator of TNF in vivo.

Reduced mast cell and basophil numbers and function in Cpa3-Cre; Mcl-1fl/fl mice.

It has been reported that the intracellular antiapoptotic factor myeloid cell leukemia sequence 1 (Mcl-1) is required for mast cell survival in vitro, and that genetic manipulation of Mcl-1 can be used to delete individual hematopoietic cell populations in vivo. In the present study, we report the generation of C57BL/6 mice in which Cre recombinase is expressed under the control of a segment of the carboxypeptidase A3 (Cpa3) promoter. C57BL/6-Cpa3-Cre; Mcl-1(fl/fl) mice are severely deficient in mast cells (92%-100% reduced in various tissues analyzed) and also have a marked deficiency in basophils (58%-78% reduced in the compartments analyzed), whereas the numbers of other hematopoietic cell populations exhibit little or no changes. Moreover, Cpa3-Cre; Mcl-1(fl/fl) mice exhibited marked reductions in the tissue swelling and leukocyte infiltration that are associated with both mast cell- and IgE-dependent passive cutaneous anaphylaxis (except at sites engrafted with in vitro-derived mast cells) and a basophil- and IgE-dependent model of chronic allergic inflammation, and do not develop IgE-dependent passive systemic anaphylaxis. Our findings support the conclusion that Mcl-1 is required for normal mast cell and basophil development/survival in vivo in mice, and also suggest that Cpa3-Cre; Mcl-1(fl/fl) mice may be useful in analyzing the roles of mast cells and basophils in health and disease.

Particle velocity estimation based on a two-microphone array and Kalman filter.

A traditional method to measure particle velocity is based on the finite difference (FD) approximation of pressure gradient by using a pair of well matched pressure microphones. This approach is known to be sensitive to sensor noise and mismatch. Recently, a double hot-wire sensor termed Microflown became available in light of micro-electro-mechanical system technology. This sensor eliminates the robustness issue of the conventional FD-based methods. In this paper, an alternative two-microphone approach termed the u-sensor is developed from the perspective of robust adaptive filtering. With two ordinary microphones, the proposed u-sensor does not require novel fabrication technology. In the method, plane wave and spherical wave models are employed in the formulation of a Kalman filter with process and measurement noise taken into account. Both numerical and experimental investigations were undertaken to validate the proposed u-sensor technique. The results have shown that the proposed approach attained better performance than the FD method, and comparable performance to a Microflown sensor.

Bayesian approach of nearfield acoustic reconstruction with particle filters.

This paper demonstrates that inverse source reconstruction can be performed using a methodology of particle filters that relies primarily on the Bayesian approach of parameter estimation. In particular, the proposed approach is applied in the context of nearfield acoustic holography based on the equivalent source method (ESM). A state-space model is formulated in light of the ESM. The parameters to estimate are amplitudes and locations of the equivalent sources. The parameters constitute the state vector which follows a first-order Markov process with the transition matrix being the identity for every frequency-domain data frame. Filtered estimates of the state vector obtained are assigned weights adaptively. The implementation of recursive Bayesian filters involves a sequential Monte Carlo sampling procedure that treats the estimates as point masses with a discrete probability mass function (PMF) which evolves with iteration. The weight update equation governs the evolution of this PMF and depends primarily on the likelihood function and the prior distribution. It is evident from the simulation results that the inclusion of the appropriate prior distribution is crucial in the parameter estimation.

Diterpene promptly executes a non-canonical autophagic cell death in doxorubicin-resistant lung cancer.

16-hydroxycleroda-3,13-dien-15,16-olide (HCD) has antitumor activity reported in numerous types of cancers. However, the efficacy of HCD treatment in non-small-cell lung cancer (NSCLC) cells and doxorubicin-resistant (Dox-R)-NSCLC cells remains to be unraveled. The underlying anti-cancer mechanism of HCD on Dox-R and Dox-sensitive (Dox-S) of A549 cells was also investigated. Cytotoxicity of HCD against two cell lines (Dox-S and Dox-R) were determined via MTT assay, flow cytometry, and Western blot. A further examination of its anti-cancer efficacy was performed in A549-bearing xenograft mice via orthotopic intratrachea (IT) inoculation, which showed that HCD could arrest both Dox-S and Dox-R cells at G2/M phase without altering the sub-G1 cycle along with increasing of cleaved-PARP. HCD downregulated the mTOR/Akt/PI3K-p85 and PI3K-ClassIII/Beclin-1 signals and upregulated p62/LC3-I/II expressions to further confirm that the cell autophagy of NSCLC cells after being HCD-induced. Morphological observations of mouse lung sections illustrated that fewer cancer cells accumulated close to the trachea while less neoplastic activities were found in HCD orthotopic treated mice without liver, kidney, and spleen toxicity. Lastly, Dox, HCD, and target therapy medicines of EGFR and ALK were nicely docked with EGFR, ALK, and mTOR. Conclusively, HCD was demonstrated the chemotherapeutic potential regardless of Dox-R and Dox-S cells, suggesting natural autophagic inducer HCD provides a promising lead compound for new drug discovery and development of lung cancer therapies.

Thymic stromal lymphopoietin contributes to myeloid hyperplasia and increased immunoglobulins, but not epidermal hyperplasia, in RabGEF1-deficient mice.

Mice overexpressing the proallergic cytokine thymic stromal lymphopoietin (TSLP) in the skin develop a pathology resembling atopic dermatitis. RabGEF1, a guanine nucleotide exchange factor for Rab5 GTPase, is a negative regulator of IgE-dependent mast cell activation, and Rabgef1-/- and TSLP transgenic mice share many similar phenotypic characteristics, including elevated serum IgE levels and severe skin inflammation, with infiltrates of both lymphocytes and eosinophils. We report here that Rabgef1-/- mice also develop splenomegaly, lymphadenopathy, myeloid hyperplasia, and high levels of TSLP. Rabgef1-/-TSLPR-/- mice, which lack TSLP/TSLP receptor (TSLPR) signaling, had levels of blood neutrophils, spleen myeloid cells, and serum IL-4, IgG1, and IgE levels that were significantly reduced compared with those in Rabgef1-/-TSLPR+/+ mice. However, Rabgef1-/-TSLPR-/- mice, like Rag1- or eosinophil-deficient Rabgef1-/- mice, developed cutaneous inflammation and epidermal hyperplasia. Therefore, in Rabgef1-/- mice, TSLP/TSLPR interactions are not required for the development of epidermal hyperplasia but contribute to the striking myeloid hyperplasia and overproduction of immunoglobulins observed in these animals. Our study shows that RabGEF1 can negatively regulate TSLP production in vivo and that excessive production of TSLP contributes to many of the phenotypic abnormalities in Rabgef1-/- mice. However, the marked epidermal hyperplasia, cutaneous inflammation, and increased numbers of dermal mast cells associated with RabGEF1 deficiency can develop via a TSLPR-independent pathway, as well as in the absence of Rag1 or eosinophils.

Mast cell-derived TNF can exacerbate mortality during severe bacterial infections in C57BL/6-KitW-sh/W-sh mice.

We used mast cell-engrafted genetically mast cell-deficient C57BL/6-Kit(W-sh/W-sh) mice to investigate the roles of mast cells and mast cell-derived tumor necrosis factor in two models of severe bacterial infection. In these mice, we confirmed findings derived from studies of mast cell-deficient WBB6F(1)-Kit(W/W-v) mice indicating that mast cells can promote survival in cecal ligation and puncture (CLP) of moderate severity. However, we found that the beneficial role of mast cells in this setting can occur independently of mast cell-derived tumor necrosis factor. By contrast, using mast cell-engrafted C57BL/6-Kit(W-sh/W-sh) mice, we found that mast cell-derived tumor necrosis factor can increase mortality during severe CLP and can also enhance bacterial growth and hasten death after intraperitoneal inoculation of Salmonella typhimurium. In WBB6F(1)-Kit(W-sh/W-sh) mice, mast cells enhanced survival during moderately severe CLP but did not significantly change the survival observed in severe CLP. Our findings in three types of genetically mast cell-deficient mice thus support the hypothesis that, depending on the circumstances (including mouse strain background, the nature of the mutation resulting in a mast cell deficiency, and type and severity of infection), mast cells can have either no detectable effect or opposite effects on survival during bacterial infections, eg, promoting survival during moderately severe CLP associated with low mortality but, in C57BL/6-Kit(W-sh/W-sh) mice, increasing mortality during severe CLP or infection with S. typhimurium.