PGE2/EP3/CXCR2 Axis Dictates Amplified Inflammatory Response during Skin Infection in Mice with Obesity.

Control of Pseudomonas aeruginosa Skin Infections in Mice Is Mast Cell-Dependent

The early events that shape the innate immune response to restrain pathogens during skin infections remain elusive. Methicillin-resistant Staphylococcus aureus (MRSA) infection engages phagocyte chemotaxis, abscess formation, and microbial clearance. Upon infection, neutrophils and monocytes find a gradient of chemoattractants that influence both phagocyte direction and microbial clearance. The bioactive lipid leukotriene B4 (LTB4) is quickly (seconds to minutes) produced by 5-lipoxygenase (5-LO) and signals through the G protein-coupled receptors LTB4R1 (BLT1) or BLT2 in phagocytes and structural cells. Although it is known that LTB4 enhances antimicrobial effector functions in vitro, whether prompt LTB4 production is required for bacterial clearance and development of an inflammatory milieu necessary for abscess formation to restrain pathogen dissemination is unknown. We found that LTB4 is produced in areas near the abscess and BLT1 deficient mice are unable to form an abscess, elicit neutrophil chemotaxis, generation of neutrophil and monocyte chemokines, as well as reactive oxygen species-dependent bacterial clearance. We also found that an ointment containing LTB4 synergizes with antibiotics to eliminate MRSA potently. Here, we uncovered a heretofore unknown role of macrophage-derived LTB4 in orchestrating the chemoattractant gradient required for abscess formation, while amplifying antimicrobial effector functions.

Staphylococcal bacteria are a common cause of skin infections in mice and humans. γδ T cells and the cytokine IL-17 are important in controlling these infections. To test roles for IL-17 in autoimmune Ets1 knockout (KO) mice, we generated double knockout (DKO) mice lacking both Ets1 and IL-17RA. We found that DKO mice develop worse autoimmune disease than Ets1 KO mice and are also susceptible to spontaneous Staphylococcus xylosus skin infections. While IL-17RA KO mice also develop skin lesions, these lesions are found at a higher rate and increased severity in DKO mice. Furthermore, exogenous infection of DKO skin with bioluminescent Staphylococcus aureus results in a failure to clear the bacteria, while IL-17RA KO mice are able to clear. Given that γδ T cells are important in controlling Staph skin infections, we examined these populations and found that both Ets1 KO and DKO mice lack the dendritic epidermal T cells (DETC), while other γδ T cell subsets are present. Further analysis showed that DETC progenitors are present in the fetal thymus of Ets1 KO mice, but DETC are missing from the skin of P5 and adult mice lacking Ets1. We hypothesized that loss of DETC (due to absence of Ets1) might cooperate with loss of IL-17 signaling (due to loss of IL-17RA) to create susceptibility to skin infections. To determine if DETC have a specific contribution to the skin immune response to Staphylococcal bacteria, we depleted DETC from wild-type mice using antibody against TCR Vγ5 followed by S. aureus infection. We found that DETC are not required to clear skin Staph infections, since depleted mice cleared with the same kinetics as non-depleted mice. Studies are in progress to further examine the roles of other γδ T cell populations in clearance of skin Staph infections. Supported by grant from NIH (R01 AI122720)

Antibiotic-resistant microbes, such as methicillin-resistant Staphylococcus aureus, seriously threaten human health. The outbreak of "superbugs" in recent years emphasizes once again the need for the development of new antimicrobial agents or resources. Antimicrobial peptides have an evident bactericidal effect against multidrug-resistant pathogens. In the present study, a new antimicrobial peptide, ctriporin, was cloned and characterized from the venom of the scorpion Chaerilus tricostatus, an animal which has not yet been explored for toxic peptide resources. The MICs of ctriporin against Staphylococcus aureus, Bacillus thuringiensis, Bacillus subtilis, Micrococcus luteus, and Candida albicans are 5 to 20 μg/ml. Meanwhile, it MIC against clinical antibiotic-resistant bacterial strains is 10 μg/ml. Furthermore, the potential for ctriporin to be used as a topical antibiotic for treating staphylococcal skin infections was investigated. External use of the peptide ctriporin dramatically decreased the bacterial counts and cured skin infections in mice. In addition, ctriporin demonstrates antimicrobial efficacy via the bactericidal mechanism of rapid cell lysis. Together, these results suggest the potential of developing ctriporin as a new topical antibiotic.

ISID1008 - The irreversible pan-caspase inhibitor emricasan is a potential host-directed immunotherapy against methicillin-resistant S. aureus (MRSA) skin infections in mice

Background: The bark oil of Dipterocarpus alatus Roxb. ex G. Don (resin tree) has been used for the treatment of ulcerated wounds in Ayurvedic medicine. However, information is still scarce about D. alatus extract and its constituents. Objectives: This study aimed to examine the antibacterial and wound healing effects of D. alatus crude extracts against methicillin-resistant Staphylococcus aureus (MRSA) in a superficial skin infection using a tape-stripping mouse model. Methods: Different parts (bark, leaves, twig, wood, and oleo-resin) of D. alatus were used for extraction. Crude extracts with two pure compounds (α,β-gurjunene and dipterocarpol) were examined for antibacterial activity against methicillin-susceptible S. aureus (MSSA) and MRSA in vitro. The in vivo antibacterial activity against MRSA was examined in a tape-stripping mouse model of superficial skin infection by evaluating transepidermal water loss (TEWL), colony counts from wound culture swabs, and H&E staining. Results: Dipterocarpus alatus twig extract showed the lowest MIC (250 µg/mL) and MBC (500 µg/mL) against MRSA among extracts from other D. alatus parts. In addition, α,β-gurjunene showed lower MIC (250 µg/mL) and MBC (250 µg/mL) against MRSA than dipterocarpol. In vivo, D. alatus twig extract significantly reduced the number of MRSA recovered from superficial wounds to levels comparable to the non-infected control group on the second day. Oleo-resin, D. alatus wood extract, α,β-gurjunene, and dipterocarpol also significantly reduced the number of MRSA. Moreover, D. alatus twig extract and dipterocarpol healed infected wounds at rates comparable to the non-infected control group. From H&E staining of wounds, fibrin accumulation and neutrophil infiltration were attenuated in mice treated with D. alatus twig extract and dipterocarpol. Conclusions: Dipterocarpus alatus twig extract and dipterocarpol possess antibacterial and wound healing properties against MRSA-induced superficial skin infection in mice.

Interleukin-1, tumour necrosis factor-alpha and interleukin-6 are considered to be major mediators of inflammatory processes. In the present study, cytokine gene transcription was detected by the polymerase chain reaction technique during cutaneous and intraperitoneal infection with herpes simplex virus-1. Epidermal cell suspensions obtained from mice infected with herpes simplex virus-1 in the ear pinna were enriched or depleted in Langerhans cells by immunomagnetic fractionation. Herpes simplex virus-1 infection in the skin was found to induce interleukin-1 beta, tumour necrosis factor-alpha and interleukin-6 gene transcription in keratinocytes at 24 hours post-infection. Gene transcription declined by 48 hours post-infection. Induction of interleukin-1 beta and tumour necrosis factor-alpha but not of IL-6 gene transcription was detected in Langerhans cells obtained from infected mice at 24 hours post-infection. In order to study cytokine gene transcription during intraperitoneal infection with herpes simplex virus-1, peritoneal exudate cells were obtained from infected mice. Maximal levels of interleukin-1 beta, tumour necrosis factor-alpha, and interleukin-6 mRNA were found in peritoneal exudate cells 6 hours after infection. RNA transcription declined at 24 hours post-infection and was no longer detectable at 48 hours post-infection. Since the higher susceptibility of newborn mice to intraperitoneal herpes simplex virus-1 infection has been suggested to be related to defective cytokine production, cytokine gene transcription was compared in peritoneal exudate cells obtained from infected newborn and adult mice. No significant differences in interleukin-1 beta, tumour necrosis factor-alpha and interleukin-6 gene expression were observed in peritoneal exudate cells obtained from newborn mice as compared with adult mice. In conclusion, cutaneous and intraperitoneal infection with herpes simplex virus-1 induces interleukin-1 beta, tumour necrosis factor-alpha and interleukin-6 gene transcription in epidermal and peritoneal exudate cells.

Topical cream-based oxyresveratrol in the treatment of cutaneous HSV-1 infection in mice

Advanced age is associated with an increased susceptibility to Coronavirus Disease (COVID)-19 and more severe outcomes, although the underlying mechanisms are understudied. The lung endothelium is located next to infected epithelial cells and bystander inflammation may contribute to thromboinflammation and COVID-19-associated coagulopathy. Here, we investigated age-associated SARS-CoV-2 pathogenesis and endothelial inflammatory responses using humanized K18-hACE2 mice. Survival was reduced to 20% in aged mice (85-112 weeks) versus 50% in young mice (12-15 weeks) at 10 days post infection (dpi). Bulk RNA-sequencing of endothelial cells from mock and infected mice at 2dpi of both age groups (aged: 72-85 weeks; young: 15 weeks) showed substantially lower significant differentially regulated genes in infected aged mice than in young mice (712 versus 2294 genes). Viral recognition and anti-viral pathways such as RIG-I-like receptor signaling, NOD-like receptor signaling and interferon signaling were regulated in response to SARS-CoV-2. Young mice showed several fold higher interferon responses (Ifitm3, Ifit1, Isg15, Stat1) and interferon-induced chemokines (Cxcl10 and Cxcl11) than aged mice. Endothelial cells from infected young mice displayed elevated expression of chemokines (Cxcl9, Ccl2) and leukocyte adhesion markers (Icam1) underscoring that inflammation of lung endothelium during infection could facilitate leukocyte adhesion and thromboinflammation. TREM1 and acute phase response signaling were particularly prominent in endothelial cells from infected young mice. Immunohistochemistry was unable to detect viral protein in pulmonary endothelium. In conclusion, our data demonstrate that the early host response of the endothelium to SARS-CoV-2 infection declines with aging, which could be a potential contributor to disease severity.

The present study was undertaken to investigate the role of exogenous and endogenous angiotensin II (Ang II) in ovarian steroidogenesis and production of prostaglandin (PG) in in vitro perfused rabbit ovaries. The addition of 100 or 10 micrograms Ang II at 2-h intervals to the perfusate did not stimulate progesterone production, but significantly stimulated estradiol (E2) production by perfused rabbit ovaries. When the specific antagonist of Ang II, saralasin at 2 x 10(-6) M, was added to the perfusate 30 min before the onset of Ang II administration, Ang II-stimulated production of E2 was significantly blocked. Ang II also significantly stimulated both PGE2 and PGF2 alpha production, while the addition of saralasin to the perfusate significantly inhibited the Ang II-stimulated production of PG. The levels of PGs in ovaries perfused with saralasin plus 100 micrograms Ang II did not differ significantly from those in control ovaries perfused with medium alone. Exposure to human CG (hCG) significantly stimulated production of progesterone and E2 by perfused rabbit ovaries, while the concomitant administration of 2 x 10(-6) M saralasin significantly reduced only E2 production. Addition of saralasin to the perfusate inhibited hCG-stimulated PG production in a dose-dependent manner. The ovulatory efficiency in ovaries treated with hCG alone or hCG plus saralasin was significantly correlated with PG production by perfused rabbit ovaries at 12 h after exposure to hCG. The production of PG stimulated by Ang II was completely reduced by indomethacin treatment during the entire perfusion period. Indomethacin completely blocked Ang II-induced ovulation, but not Ang II-stimulated oocyte maturation. Concurrent administration of staurosporine, a protein kinase C inhibitor, at 10(-6) M significantly inhibited Ang II-stimulated meiotic maturation of ovulated ova and follicular oocytes. In conclusion, these results indicate that Ang II has a direct role in ovarian production of E2 and PG. An intrinsic renin-angiotensin system in the rabbit ovary may act as an intermediary of gonadotropin-stimulated PG production. Locally produced Ang II may induce ovulation in the rabbit ovary, at least in part, by stimulating PG production.

BackgroundInfluenza is an acute viral respiratory illness that causes high morbidity and mortality globally. Therapeutic actions are limited to vaccines and a few anti-viral drugs. Polygala (P.) japonica herba is rich in Polygalasaponin F (PSF, C53H86O23), used for acute bronchitis, pharyngitis, pneumonia, amygdalitis, and respiratory tract infections treatment in China. Hypercytokinemia is often correlated with severe pneumonia caused by several influenza viruses. PSF was reported to have anti-inflammatory effects and its mechanism is associated with the nuclear factor (NF)-κB signaling pathway. The action of PSF to alleviate pulmonary inflammation caused by influenza A virus (IAV) infection requires careful assessment. In the present study, we evaluated the effect and mechanism of PSF on mice with pneumonia caused by influenza H1N1 (A/FM/1/47).MethodsMice were infected intranasally with fifteen 50% mouse lethal challenge doses (MLD50) of influenza virus. BALB/c mice were treated with PSF or oseltamivir (oral administration) for 2 h post-infection and received concomitant treatment for 5 days after infection. On day 6 post-infection, 10 mice per group were killed to collect related samples, measure body weight and lung wet weight, and detect the viral load, cytokine, prostaglandins, pathological changes, and cell pathway protein expression in the lungs. In addition, the survival experiments were carried out to investigate the survival of mice. The expression profile of cell pathway proteins was detected and analyzed using a broad pathway antibody array and confirmed the findings from the array by western blotting.ResultsPolygalasaponin F and oseltamivir can protect against influenza viral infection in mice. PSF and oseltamivir significantly relieved the signs and symptoms, reduced body weight loss, and improved the survival rate of H1N1-infected mice. Moreover, PSF efficiently decreased the level of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-4, interferon (IFN)-γ, thromboxane A2 (TXA2), and prostaglandin E2 (PGE2) in lung tissues of mice infected with influenza virus (p < 0.05–0.01). Oseltamivir had a similar effect to lung cytokine of PSF, but did not decrease the levels of TXA2 and PGE2. There was a twofold or greater increase in four cell pathway protein, namely NF-κB p65 (2.68-fold), I-kappa-B-alpha (IκBα) (2.56-fold), and MAPK/ERK kinase 1 (MEK1) (7.15-fold) assessed in the array induced by influenza virus. Western blotting showed that the expression of these proteins was significantly decreased in lung after influenza virus challenge in PSF and oseltamivir-treated mice (p < 0.05–0.01).ConclusionPolygalasaponin F appears to be able to augment protection against IAV infection in mice via attenuation of pulmonary inflammatory responses. Its effect on IAV-induced pulmonary inflammation was associated with suppression of Raf/MEK/ERK and NF-κB expressions.

Description Obesity is a comorbidity for viral infections in the lungs, but the impact of obesity on bacterial lung infections is poorly understood. Utilizing a diet-induced obesity (DIO) mouse model, we previously found that obese mice were more resistant to infection with the virulent bacterium Francisella tularensis (Ft) SchuS4, and an early COX-derived prostaglandins (PG) production, correlated with increased survival. However, we did not determine if this outcome was specific to Ft and if a specific PG mediated the protective response. In this study, DIO and regular weight (RW) mice were intranasally challenged with Ft SchuS4, attenuated Ft LVS, and Bordetella pertussis (Bp). Regardless of the infecting agent, DIO mice were more resistant to infection, had elevated levels of PG and improved inflammatory responses in the lung compared to RW mice. Improved control of inflammation in DIO lungs after infection was associated with decreased cell death and changes in efferocytosis among DIO mice compared to RW mice. We then identified the PG responsible for the protective effects observed in DIO mice. In contrast to PGE2, PGD2 and its metabolites, dampened inflammatory responses following infection of macrophages with Ft or Bp. However, the mechanism of this protection was dependent on the infecting bacterium. Together these data demonstrate that an early production of PGD2 in obesity has important contributions to the relative susceptibility of the host to pulmonary bacterial infection. Funding Sources Supported by the Intramural Research Program of the National Institute of Allergy and Infectious Diseases, National Institutes of Health. Topic Categories Microbial, Parasitic, and Fungal Immunology (MPF)

Chemokine responses and accumulation of inflammatory cells in the lungs of mice infected with highly virulent Cryptococcus neoformans: effects of interleukin-12.

Growth hormone attenuates the brain damage caused by ZIKV infection in mice

The role of fetal membranes in regulating production, transport, and metabolism of prostaglandin E2 during labor