Stimulation of muscle protein degradation by murine and human epidermal cytokines: relationship to thermal injury

Purification of PaTx-II from the Venom of the Australian King Brown Snake and Characterization of Its Antimicrobial and Wound Healing Activities

Infections caused by multi-drug-resistant (MDR) bacteria are a global threat to human health. As venoms are the source of biochemically diverse bioactive proteins and peptides, we investigated the antimicrobial activity and murine skin infection model-based wound healing efficacy of a 13 kDa protein. The active component PaTx-II was isolated from the venom of Pseudechis australis (Australian King Brown or Mulga Snake). PaTx-II inhibited the growth of Gram-positive bacteria in vitro, with moderate potency (MICs of 25 µM) observed against S. aureus, E. aerogenes, and P. vulgaris. The antibiotic activity of PaTx-II was associated with the disruption of membrane integrity, pore formation, and lysis of bacterial cells, as evidenced by scanning and transmission microscopy. However, these effects were not observed with mammalian cells, and PaTx-II exhibited minimal cytotoxicity (CC₅₀ > 1000 µM) toward skin/lung cells. Antimicrobial efficacy was then determined using a murine model of S. aureus skin infection. Topical application of PaTx-II (0.5 mg/kg) cleared S. aureus with concomitant increased vascularization and re-epithelialization, promoting wound healing. As small proteins and peptides can possess immunomodulatory effects to enhance microbial clearance, cytokines and collagen from the wound tissue samples were analyzed by immunoblots and immunoassays. The amounts of type I collagen in PaTx-II-treated sites were elevated compared to the vehicle controls, suggesting a potential role for collagen in facilitating the maturation of the dermal matrix during wound healing. Levels of the proinflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2) and interleukin-10 (IL-10), factors known to promote neovascularization, were substantially reduced by PaTx-II treatment. Further studies that characterize the contributions towards efficacy imparted by in vitro antimicrobial and immunomodulatory activity with PaTx-II are warranted.

Diagnosis-dependent relationships between cytokine levels and survival in patients admitted for surgical critical care

BACKGROUND

Death after trauma, infection, or other critical illness has been attributed to unbalanced inflammation, in which dysregulation of cytokines leads to multiple organ dysfunction and death. We hypothesized that admission cytokine profiles associated with death would differ based on admitting diagnosis.

STUDY DESIGN

This 5-year study included patients admitted for trauma or surgical intensive care for more than 48 hours at 2 academic, tertiary care hospitals between October 2001 and May 2006. Cytokine analysis for interleukin (IL)-1, -2, -4, -6, -8, -10, -12, interferon-gamma, and tumor necrosis factor (TNF)-alpha was performed using ELISA on specimens drawn within 72 hours of admission. Mann-Whitney U test was used to compare median admission cytokine levels between alive and deceased patients. Relative risks and odds of death associated with admission cytokines were generated using univariate analysis and multivariate logistic regression models, respectively.

RESULTS

There were 1,655 patients who had complete cytokine data: 290 infected, nontrauma; 343 noninfected, nontrauma; and 1,022 trauma. Among infected patients, nonsurvivors had higher median admission levels of IL-2, -8, -10, and granulocyte macrophage-colony stimulating factor; noninfected, nontrauma patients had higher IL-6, -8, and IL-10; and nonsurviving trauma patients had higher IL-4, -6, -8, and TNF-alpha. IL-4 was the most significant predictor of death and carried the highest relative risk of dying in trauma patients, and IL-8 in nontrauma, noninfected patients. In infected patients, no cytokine independently predicted death.

CONCLUSIONS

Cytokine profiles of certain disease states may identify persons at risk of dying and allow for selective targeting of multiple cytokines to prevent organ dysfunction and death.

Disruption of interleukin-1 signaling improves the quality of wound healing

In this study, we investigated the role of interleukin (IL)-1 signaling in wound healing. IL-1 receptor type I (IL-1R) knockout (KO) mice showed reduced fibrosis in both cutaneous and deep tissue wounds, which was accompanied by a reduction in inflammatory cellular infiltration in cutaneous but not in deep tissue wounds. There were no differences in either total collagenolytic activity or in the expression of selected matrix metalloproteinases or tissue inhibitors of metalloproteinases between the wound fluids from wild-type or IL-1R KO mice. However, wound fluids from IL-1R KO mice contained lower levels of IL-6 compared with wild-type controls. In addition, the infusion of IL-6 into wounds in IL-1R KO mice did not increase fibrosis. Skin wounds in IL-1R KO animals had lower levels of collagen and improved restoration of normal skin architecture compared with skin wounds in wild-type mice. However, neither the tensile strength of incisional skin wounds nor the rate of closure of excisional wounds differed between IL-1R KO and wild-type animals. The reduced fibrotic response in wounds from IL-1R KO mice could be reproduced by the administration of an IL-1R antagonist. These findings suggest that pharmacological interference with IL-1 signaling could have therapeutic value in the prevention of hypertrophic scarring and in the treatment of fibrotic diseases.

Toward a theory regarding the pathogenesis of the systemic inflammatory response syndrome: what we do and do not know about cytokine regulation

OBJECTIVES

The systemic inflammatory response syndrome (SIRS) is the massive inflammatory reaction resulting from systemic mediator release that may lead to multiple organ dysfunction. The objective of this review article is to analyze the roles of cytokines, cytokine production, and the relationship of cytokine production to the development of SIRS.

DATA SOURCES

Previous research and clinical studies related to cytokines and their relationship to SIRS.

STUDY SELECTION

From the studies reviewed, three critical questions are addressed. First, what is the definition of increased cytokine concentrations? Second, what other systemic illnesses besides sepsis can alter cytokine concentrations? Third, what are the right cytokines to measure?

DATA SYNTHESIS

This article postulates a three-stage development of SIRS, in which stage 1 is a local production of cytokines in response to an injury or infection. Stage 2 is the protective release of a small amount of cytokines into the body's circulation. Stage 3 is the massive systemic reaction where cytokines turn destructive by compromising the integrity of the capillary walls and flooding end organs.

CONCLUSIONS

While cytokines are generally viewed as a destructive development in the patient that generally leads to multiple organ dysfunction, cytokines also protect the body when localized. It will be necessary to study the positive effects of cytokines while also studying their role in causing SIRS. It will also be important to investigate the relationship between cytokines and their blockers in SIRS.

Role of growth factors in cutaneous wound healing: a review

The well-orchestrated, complex series of events resulting in the repair of cutaneous wounds are, at least in part, regulated by polypeptide growth factors. This review provides a detailed overview of the known functions, interactions, and mechanisms of action of growth factors in the context of the overall repair process in cutaneous wounds. An overview of the cellular and molecular events involved in soft tissue repair is initially presented, followed by a review of widely studied growth factors and a discussion of commonly utilized preclinical animal models. The article concludes with a summary of the preliminary results from human clinical trials evaluating the effects of growth factors in the healing of chronic skin ulcers. Throughout, the interactions among the growth factors in the wound-healing process are emphasized.

Expression of interleukin 1 in burn scars

A histochemical study using a Biotin-Streptavidin procedure for demonstrating interleukin 1 (IL-1) in burn scar specimens is described. Among seventeen scar specimens, five positive reactions to IL-1 were observed in the epidermis. No positive reactions in the dermal tissue, however, were detected. The twenty specimens of normal skin used as controls showed no positive reaction in either the dermis or the dermis.

Alpha-melanocyte stimulating hormone modulates contact hypersensitivity responsiveness in C57/BL6 mice

The neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) can act as an antagonist to interleukin 1 (IL-1) bioactivities such as inhibition of fever production, thymocyte proliferation, and inhibition of release of acute phase inflammatory molecules from the liver. In this report we have found that epicutaneous application of alpha-MSH suppresses both the sensitization and elicitation limbs of the cutaneous immune response (CIR) to potent contact sensitizers like dinitrofluorobenzene (DNFB) or oxazalone (OX) in mice. Further, the loss of contact hypersensitivity due to applications of alpha-MSH could be reconstituted by either intradermal or intravenous injections of epidermal thymocyte activating factor (ETAF)/interleukin-1. Topical application of alpha-MSH did not cause an alteration in Ia+ dendritic cells (i.e., Langerhans cells) but did produce a significant reduction in the expression of Thy1.2 marker on the Thyl+ dendritic epidermal cells (Thy1+DEC). It has no effects on the phenotypic expression of asialo GM-1 on these same cells. These observations suggest that alpha-MSH, a peptide classically isolated from the pituitary but found in many other tissues and cells of the body, may represent an additional biologic modifier than can modulate suppression of the contact hypersensitivity responses to various haptens. However, the mechanisms by which alpha-MSH or potentially other peptides found in the skin produce these suppressive effects have not been elucidated.

Interleukin-1 and the response to injury

Traumatic injury is the leading cause of morbidity and mortality in Americans less than 45 years old. People surviving the initial insult undergo metabolic, hemodynamic and immunologic changes which contribute to both early and late complications. Though necessary for normal immunologic response and for wound healing, pathologic alterations of IL-1 synthesis, degradation, and binding to receptors on both a local and systemic level could lead to these changes. Manipulation of IL-1-mediated effects might be of therapeutic utility in the management of trauma in the future.

Inhibition of the induction of contact hypersensitivity by an epithelial cell-derived interleukin-1 inhibitor

Interleukin-1 (IL-1) is the central hormone of acute inflammation. Previous studies have demonstrated that an Interleukin-1 inhibitor (ILS) derived from human gingival epithelial cell cultures abrogates the effect of IL-1 on human Langerhans cells and murine thymocytes in vitro. The present study investigated the effect of ILS on the induction and elicitation of contact hypersensitivity (CHS) to 2,4-dinitro-1-fluorobenzene (DNFB). Systemic administration of ILS 6 days prior to sensitisation significantly blocked the induction of CHS to DNFB in Balb/c mice. In addition, i.v. injection of ILS 24 or 48 hours prior to the elicitation of CHS produced a reduction in ear swelling, but the suppressive effect was less profound than when ILS was administered prior to sensitisation. Thus, ILS production by epithelial cells is a possible mechanism for the down-regulation of cutaneous immune responses.

Biology and molecular biology of epidermal cell-derived thymocyte activating factor

ETAF/IL-1 has a multiplicity of divergent biological effects: enhancement of thymocyte proliferation, stimulation of cells in the hypothalamus to mediate fever, leukocyte chemotaxis, stimulation of hepatic synthesis of acute-phase proteins, augmentation of IL-2 production and keratinocyte proliferation. Until recently, it has not been possible to determine whether these divergent activities are mediated by closely related cytokines or separate cytokines. Now with the identification of IL-1 alpha, IL-1 beta and IL-1k from keratinocytes, these studies will become possible. In either case, it is likely that ETAF/IL-1 plays an important role in local cutaneous and systemic inflammatory and immunological events.