Anti-tumor necrosis factor-alpha therapy during murine Klebsiella pneumoniae bacteremia: increased mortality in the absence of liver injury.

Klebsiella pneumoniae is a leading cause of gram-negative bacterial pneumonia, often resulting in bacteremia concurrent with the localized pulmonary infection. The beneficial role of tumor necrosis factor (TNF)-alpha during pulmonary infection has been well documented; however, consequences of TNF-alpha production during systemic bacterial infection are controversial. A murine model of K. pneumoniae was developed to address this important issue. Liver-associated TNF-alpha mRNA was induced within 30 min after intravenous bacterial inoculation and remained elevated through 6 h before returning to near-baseline at 24 h postinfection. Intravenous K. pneumoniae infection induced liver cellular injury that was completely ablated when mice were pretreated with a neutralizing anti-TNF-alpha antibody. Interestingly, this reduction in liver injury failed to translate into improved survival. Mice receiving anti-TNF-alpha continued to succumb to the infection even out to day 10 postinfection. Bacterial clearance after TNF-alpha neutralization was significantly impaired at later time points during infection. Correlating with impaired bacterial clearance was diminished production of liver-associated MIP-2, MIP-1alpha, MCP-1, and interferon-gamma. Further evidence of diminished antibacterial immune responses was noted when the activational status of splenic natural killer cells in anti-TNF-alpha-treated mice was examined 24 h postinfection. Natural killer cells displayed decreased CD69 expression. Combined, these data indicate that the beneficial effects of TNF-alpha during systemic K. pneumoniae infection outweigh the detrimental effects of TNF-alpha-mediated hepatocyte cellular injury. Anti-TNF-alpha therapy, although preventing liver injury during blood-borne bacterial infection, results in a dampened anti-bacterial host response, resulting in decreased bacterial clearance and overall survival

TLR2 expression is increased in rosacea and stimulates enhanced serine protease production by keratinocytes.

A diverse environment challenges skin to maintain temperature, hydration, and electrolyte balance while also maintaining normal immunological function. Rosacea is a common skin disease that manifests unique inflammatory responses to normal environmental stimuli. We hypothesized that abnormal function of innate immune pattern recognition could explain the enhanced sensitivity of patients with rosacea, and observed that the epidermis of patients with rosacea expressed higher amounts of Toll-like receptor 2 (TLR2) than normal patients. Increased expression of TLR2 was not seen in other inflammatory skin disorders such as atopic dermatitis or psoriasis. Overexpression of TLR2 on keratinocytes, treatment with TLR2 ligands, and analysis of TLR2-deficient mice resulted in a calcium-dependent release of kallikrein 5 from keratinocytes, a critical protease involved in the pathogenesis of rosacea. These observations show that abnormal TLR2 function may explain enhanced inflammatory responses to environmental stimuli and can act as a critical element in the pathogenesis of rosacea

Defective innate antibacterial host responses during murine Klebsiella pneumoniae bacteremia: tumor necrosis factor (TNF) receptor 1 deficiency versus therapy with anti-TNF-alpha.

Klebsiella pneumoniae is a leading cause of pneumonia due to gram-negative bacteria. A significant clinical complication of pulmonary infection with K. pneumoniae is peripheral blood dissemination, which results in a systemic infection coincident with the localized pulmonary infection. This study describes the critical importance of tumor necrosis factor (TNF) receptor 1 (TNFR1)-mediated signaling during K. pneumoniae bacteremia. TNFR1-deficient mice displayed a significantly increased mortality rate after intravenous inoculation. Unexpectedly, this increased mortality occurred in the absence of either increased bacterial burden or increased liver injury. However, excessive production of proinflammatory cytokines, including TNF-alpha , was observed in TNFR1-deficient mice, compared with that observed in infected C57BL/6 mice, which suggests that production was dysregulated in the absence of TNFR1 signaling. In contrast, other experiments examined the effect of immunotherapy with anti-TNF-alpha during K. pneumoniae bacteremia. Administration of a neutralizing anti-TNF-alpha antibody completely ablated K. pneumoniae-induced liver injury. This reduction in liver injury failed to translate into an improved survival rate, because mice died of the infection as late as 10 days after infection. Bacterial clearance after neutralization of TNF-alpha was significantly impaired at later time points during infection. Diminished production of liver-associated cytokines and chemokines correlated with impaired bacterial clearance, which suggests that antibacterial immune responses were dampened. These data indicate that the antibacterial host response is dysregulated in mice lacking TNFR1 or TNF-alpha bioactivity

β2-Microglobulin-Dependent Bacterial Clearance and Survival during Murine Klebsiella pneumoniae Bacteremia ▿

Klebsiella pneumoniae is a leading cause of both community-acquired and nosocomial gram-negative bacterial pneumonia. A significant clinical complication of Klebsiella pulmonary infections is peripheral blood dissemination, resulting in a systemic infection concurrent with the localized pulmonary infection. We report here on the critical importance of β2-microglobulin expression during murine K. pneumoniae bacteremia. β2-Microglobulin knockout mice displayed significantly increased mortality upon intravenous inoculation that correlated with increased bacterial burden in the blood, liver, and spleen. As β2-microglobulin knockout mice lack both CD8+ T cells and invariant NK T cells, mouse models specifically deficient in either cell population were examined to see if this would account for the increased mortality noted in β2-microglobulin knockout mice. Surprisingly, neither CD8 T-cell-deficient (TAP-1 knockout; in vivo anti-CD8 antibody treatment) nor invariant NK (iNK) T-cell-deficient (CD1d knockout, Jα281 knockout) mice were more susceptible to K. pneumoniae bacteremia. Combined, these studies clearly indicate the importance of a β2-microglobulin-dependent but CD8 T-cell- and iNK T-cell-independent mechanism critical for survival during K. pneumoniae bacteremia

Staphylococcus epidermidis antimicrobial delta-toxin (phenol-soluble modulin-gamma) cooperates with host antimicrobial peptides to kill group A Streptococcus.

Antimicrobial peptides play an important role in host defense against pathogens. Recently, phenol-soluble modulins (PSMs) from Staphylococcus epidermidis (S. epidermidis) were shown to interact with lipid membranes, form complexes, and exert antimicrobial activity. Based on the abundance and innocuity of the cutaneous resident S. epidermidis, we hypothesized that their PSMs contribute to host defense. Here we show that S. epidermidis delta-toxin (PSMgamma) is normally present in the epidermis and sparsely in the dermis of human skin using immunohistochemistry. Synthetic delta-toxin interacted with neutrophil extracellular traps (NETs) and colocalized with cathelicidin while also inducing NET formation in human neutrophils. In antimicrobial assays against Group A Streptococcus (GAS), delta-toxin cooperated with CRAMP, hBD2, and hBD3. In whole blood, addition of delta-toxin exerted a bacteriostatic effect on GAS, and in NETs, delta-toxin increased their killing capacity against this pathogen. Coimmunoprecipitation and tryptophan spectroscopy demonstrated direct binding of delta-toxin to host antimicrobial peptides LL-37, CRAMP, hBD2, and hBD3. Finally, in a mouse wound model, GAS survival was reduced (along with Mip-2 cytokine levels) when the wounds were pretreated with delta-toxin. Thus, these data suggest that S. epidermidis-derived delta-toxin cooperates with the host-derived antimicrobial peptides in the innate immune system to reduce survival of an important human bacterial pathogen

Isl1Cre reveals a common Bmp pathway in heart and limb development.

A number of human congenital disorders present with both heart and limb defects, consistent with common genetic pathways. We have recently shown that the LIM homeodomain transcription factor islet 1 (Isl1) marks a subset of cardiac progenitors. Here, we perform lineage studies with an Isl1Cre mouse line to demonstrate that Isl1 also marks a subset of limb progenitors. In both cardiac and limb progenitors, Isl1 expression is downregulated as progenitors migrate in to form either heart or limb. To investigate common heart-limb pathways in Isl1-expressing progenitors, we ablated the Type I Bmp receptor, Bmpr1a utilizing Isl1Cre/+. Analysis of consequent heart and limb phenotypes has revealed novel requirements for Bmp signaling. Additionally, we find that Bmp signaling in Isl1-expressing progenitors is required for expression of T-box transcription factors Tbx2 and Tbx3 in heart and limb. Tbx3 is required for heart and limb formation, and is mutated in ulnar-mammary syndrome. We provide evidence that the Tbx3 promoter is directly regulated by Bmp Smads in vivo

TLR2 expression is increased in rosacea and stimulates enhanced serine protease production by keratinocytes.

A diverse environment challenges skin to maintain temperature, hydration, and electrolyte balance while also maintaining normal immunological function. Rosacea is a common skin disease that manifests unique inflammatory responses to normal environmental stimuli. We hypothesized that abnormal function of innate immune pattern recognition could explain the enhanced sensitivity of patients with rosacea, and observed that the epidermis of patients with rosacea expressed higher amounts of Toll-like receptor 2 (TLR2) than normal patients. Increased expression of TLR2 was not seen in other inflammatory skin disorders such as atopic dermatitis or psoriasis. Overexpression of TLR2 on keratinocytes, treatment with TLR2 ligands, and analysis of TLR2-deficient mice resulted in a calcium-dependent release of kallikrein 5 from keratinocytes, a critical protease involved in the pathogenesis of rosacea. These observations show that abnormal TLR2 function may explain enhanced inflammatory responses to environmental stimuli and can act as a critical element in the pathogenesis of rosacea

Increased Mortality and Dysregulated Cytokine Production in Tumor Necrosis Factor Receptor 1-Deficient Mice following Systemic Klebsiella pneumoniae Infection

A significant clinical complication of pulmonary infections with Klebsiella pneumoniae is peripheral blood dissemination, resulting in a systemic infection concurrent with the localized pulmonary infection. In this context, little is known about the role of tumor necrosis factor receptor 1 (TNFR1)-mediated innate immune responses during systemic Klebsiella infections. Mice lacking TNFR1 were significantly more susceptible to Klebsiella-induced mortality following intravenous inoculation. Bacterial clearance was impaired in TNFR1-deficient mice at early times following infection. Unexpectedly, bacterial burdens at the onset of mortality (days 2 to 3 postinfection) were not higher in mice lacking TNFR1. However, elevated production of liver-associated proinflammatory cytokines (interleukin-12, tumor necrosis factor alpha [TNF-α[, and gamma interferon [IFN-γ]) and chemokines (MIP-1α, MIP-2, and MCP-1) was observed within the first 24 h of infection. Additionally, excessive plasma-associated IFN-γ was also observed late in the course of infection (day 3). Spleen cells from day-3 infected TNFR1-deficient mice secreted markedly enhanced levels of IFN-γ when cultured in vitro. Additionally, there was a marked increase in the total number of activated lymphocyte subsets as indicated by CD69 upregulation. A notable exception was the sharp decrease in the frequency of splenic NK T cells in infected TNFR1 knockout (KO) mice. Anti-TNF-α therapy in TNFR1 KO mice significantly reduced chemokine production and liver injury. Combined, these data indicate a dysregulated antibacterial host response following intravenous Klebsiella infection in the absence of TNFR1 signaling, resulting in heightened cytokine production and hyperactivation of specific splenic lymphocyte subsets