Pro-inflammatory chemokine CCL2 (MCP-1) promotes healing in diabetic wounds by restoring the macrophage response.

Prior studies suggest that the impaired healing seen in diabetic wounds derives from a state of persistent hyper-inflammation characterized by harmful increases in inflammatory leukocytes including macrophages. However, such studies have focused on wounds at later time points (day 10 or older), and very little attention has been given to the dynamics of macrophage responses in diabetic wounds early after injury. Given the importance of macrophages for the process of healing, we studied the dynamics of macrophage response during early and late phases of healing in diabetic wounds. Here, we report that early after injury, the diabetic wound exhibits a significant delay in macrophage infiltration. The delay in the macrophage response in diabetic wounds results from reduced Chemokine (C-C motif) ligand 2 (CCL2) expression. Importantly, one-time treatment with chemoattractant CCL2 significantly stimulated healing in diabetic wounds by restoring the macrophage response. Our data demonstrate that, rather than a hyper-inflammatory state; the early diabetic wound exhibits a paradoxical and damaging decrease in essential macrophage response. Our studies suggest that the restoration of the proper kinetics of macrophage response may be able to jumpstart subsequent healing stages. CCL2 chemokine-based therapy may be an attractive strategy to promote healing in diabetic wounds.

Lessons learned from psoriatic plaques concerning mechanisms of tissue repair, remodeling, and inflammation.

Following injury, skin establishes a balance between too little inflammation increasing risk of infection, and excessive inflammation contributing to delayed wound healing and scarring. Mounting evidence indicates both initiation and termination of inflammation involve active mechanisms. Not only does inflammation itself seem to be a paradox because inflammatory responses are both essential and potentially detrimental, but one chronic inflammatory skin disease (e.g. psoriasis) presents additional paradoxes. While plaques share several factors with wound healing, two understudied and puzzling aspects include why do not inflamed plaques more frequently transform?; and why do not plaques result in scarring? To get at these questions, we review responses involved in wound repair. Oral mucosa was probed because, like fetal skin, wound repair is characterized by its rapidity, low inflammation, and scarless resolution. Active roles for macrophages as both initiators and terminators of inflammation are highlighted. Therapeutic implications are discussed regarding psoriasis and pyoderma gangrenosum. Based on biochemical and immunohistochemical considerations linking psoriatic plaques to hard palate, a novel metaplastic model is presented. We hypothesize saliva and chronic trauma contribute to a constitutive epithelial program where keratinocyte proliferation is more intense prior to differentiation, accompanied by keratin 16 expression in hard palate, thereby resembling plaques. Rather than viewing psoriasis as a nonspecific response to inflammation, we postulate a metaplastic switch by which prepsoriatic skin is converted to a distinct adult tissue type resembling hard palate. In summary, many lessons can be learned by focusing on complex processes involved in regulation of inflammation, tissue repair, and remodeling.

Etanercept responsive acrodermatitis continua of Hallopeau: is a pattern developing?

Acrodermatitis continua of Hallopeau (ACH) is a rare disease. Little is known about its etiology or relative effectiveness of the various therapeutic approaches. However, in the literature a pattern seems to be developing on successfully treated patients using biologic therapies. Here, we further emphasize the potential breakthrough presented by the novel immune based therapies. This report consists of a case of etanercept responsive ACH along with a brief review of the literature.

Proteasome inhibitors trigger NOXA-mediated apoptosis in melanoma and myeloma cells.

Patients with metastatic melanoma or multiple myeloma have a dismal prognosis because these aggressive malignancies resist conventional treatment. A promising new oncologic approach uses molecularly targeted therapeutics that overcomes apoptotic resistance and, at the same time, achieves tumor selectivity. The unexpected selectivity of proteasome inhibition for inducing apoptosis in cancer cells, but not in normal cells, prompted us to define the mechanism of action for this class of drugs, including Food and Drug Administration-approved bortezomib. In this report, five melanoma cell lines and a myeloma cell line are treated with three different proteasome inhibitors (MG-132, lactacystin, and bortezomib), and the mechanism underlying the apoptotic pathway is defined. Following exposure to proteasome inhibitors, effective killing of human melanoma and myeloma cells, but not of normal proliferating melanocytes, was shown to involve p53-independent induction of the BH3-only protein NOXA. Induction of NOXA at the protein level was preceded by enhanced transcription of NOXA mRNA. Engagement of mitochondrial-based apoptotic pathway involved release of cytochrome c, second mitochondria-derived activator of caspases, and apoptosis-inducing factor, accompanied by a proteolytic cascade with processing of caspases 9, 3, and 8 and poly(ADP)-ribose polymerase. Blocking NOXA induction using an antisense (but not control) oligonucleotide reduced the apoptotic response by 30% to 50%, indicating a NOXA-dependent component in the overall killing of melanoma cells. These results provide a novel mechanism for overcoming the apoptotic resistance of tumor cells, and validate agents triggering NOXA induction as potential selective cancer therapeutics for life-threatening malignancies such as melanoma and multiple myeloma.

Uncovering histologic criteria with prognostic significance in toxic epidermal necrolysis.

OBJECTIVE: To identify histologic criteria and prognostic significance in patients with toxic epidermal necrolysis (TEN), a frequently lethal disease that usually represents an adverse drug reaction. DESIGN: Retrospective analysis of clinical records and histologic material from a 10-year period (1994-2004). Two investigators blinded to clinical data reviewed hematoxylin-eosin-stained sections. SETTING: North American tertiary care, university-based burn unit. Patients Thirty-seven patients treated for TEN between 1994 and 2004 who had sloughing of 30% or more of their total body surface area and who underwent skin punch biopsies immediately following admission. Main Outcome Measure The degree of dermal mononuclear (DM) inflammation was graded (sparse, moderate, or extensive) at least 2 high-power fields (HPF) away from the perimeter of epidermal detachment, and the mean number of DM cells/5 HPF was quantified for each patient. Clinical records were reviewed and the following data extracted: age, history of cancer, percentage of total body surface area slough, heart rate, and serum glucose, bicarbonate, and serum urea nitrogen values on admission. Severity scores for TEN (SCORTEN) were calculated, and clinical outcome was recorded as survived or died during hospitalization. RESULTS: Extent of inflammation was assessed by categorizing the mean +/- SD DM cell counts as follows: sparse, 161 +/- 36 cells/HPF (n = 15); moderate, 273 +/- 76 cells/HPF (n = 15); and extensive, 392 +/- 124 cells/HPF (n = 7). There was good concordance between observer ratings (P<.001). While 73% of patients (n = 11) with sparse inflammation survived, only 47% (n = 7) with moderate and 29% (n = 2) with extensive inflammation survived. The accuracy in predicting patient outcome was 65% using grade of inflammation, 68% with mean cell count, and 71% with SCORTEN. CONCLUSIONS: There is a histologic spectrum with TEN that ranges from sparse to extensive DM inflammation, and degree of inflammation predicts clinical outcome approximately as well as SCORTEN. Future clinical trials should consider the possibility that various patient subsets exist within the TEN population, and a role for immunocytes needs to be critically reevaluated in this devastating disease.

Role for Id-1 in immunobiology of normal keratinocytes and in basal cell carcinoma.

It has been established that Id proteins can block the basic helix-loop-helix (HLH) transcription factors, thereby impacting the onset of senescence in keratinocytes, as well as influencing tumorigenesis involving squamous cell carcinomas. However, the ability of Id-1 to influence the immunologic response of epithelial cells to cytokines implicated in cutaneous oncology such as gamma interferon (IFN-gamma) has not been determined. Using a whole population of human keratinocytes infected with a retrovirus to induce over-expression of Id-1, the influence on early differentiation of rapidly proliferating keratinocytes was assessed, as was the response to IFN-gamma. While induction of involucrin, a marker of early differentiation, was not altered in Id-1 overexpressing keratinocytes, the IFN-gamma mediated increase in intercellular adhesion molecule-1 (ICAM-1) and HLA-DR was reduced. No change in constitutive or inducible levels of MHC class I antigen, CD95 (Fas antigen) or LFA-3 (CD58) was observed in this system. Immunostaining and Western blot analysis revealed over-expression of Id-1 in basal cell carcinomas (BCCs). These tumors not only strongly and diffusely expressed Id-1, but were also characterized by reduced ICAM-1 and HLA-DR expression. Thus, dysregulated Id-1 may not only contribute to delaying the senescence program in keratinocytes, it may also contribute to the escape of the relatively undifferentiated tumor cells in BCC from immune surveillance.

Innate immune-related receptors in normal and psoriatic skin.

CONTEXT: A precise role for the innate immune system in psoriasis remains to be determined. Surface receptors, including Toll-like receptors (TLRs) that recognize bacterial ligands and CD91, which recognizes heat shock proteins (HSPs), are implicated in both innate and adaptive immunity. OBJECTIVE: Since skin is exposed to various exogenous stimuli, which can provoke or exacerbate psoriasis, we characterized expression and function of TLRs, CD91, and HSPs in normal and psoriatic skin. DESIGN: A variety of skin-derived cells and blood-derived cells were analyzed both in vivo and in vitro; samples were obtained from 24 different individuals for innate immune-related receptor expression and function. By comparing and contrasting individuals with healthy skin and psoriatic patients, several specific differences were identified. RESULTS: Immunohistochemistry-based expression profiling revealed TLR1 expression in epidermal dendritic cells (DCs) and dermal dendritic cells (DDCs) in normal skin, as well as in pre-psoriatic skin and psoriatic plaques, with enhanced basal layer keratinocyte (KC) expression in pre-psoriatic and psoriatic plaques compared with normal skin; TLR2 expression primarily by DDCs; and TLR4 expression by epidermal DCs and DDCs, with mid-epidermal-layer KCs displaying cell surface staining. No TLR9 or CD14 was detected on DCs or KCs, although psoriatic plaques contained CD14-positive macrophages. Analysis of psoriatic epidermis revealed HSPs 27, 60, and 70. Keratinocytes were CD91 negative, but CD91 was expressed by fibroblasts and DDCs in normal and pre-psoriatic skin, with prominent accumulation of CD91-positive DDCs in psoriatic plaques. Cultured KCs revealed no surface expression of TLR2, TLR4, TLR9, or CD91. Exposure of fibroblasts, but not KCs, to lipopolysaccharide or HSPs triggered nuclear factor (NF)-kappaB activation. Heat shock proteins did induce maturation of blood-derived DCs accompanied by increased interleukin-12 production and enhanced antigen-presenting function. CONCLUSIONS: These data demonstrate distinctive patterns of innate immune-related receptors by specific subsets of cells in normal and psoriatic skin, suggesting functional roles for HSPs and DCs in psoriasis.

Pathways involved in proliferating, senescent and immortalized keratinocyte cell death mediated by two different TRAIL preparations.

Properly regulated keratinocyte cell death is fundamentally important to maintain structural integrity and homeostatic function of epidermis. Moreover, from an oncological perspective, therapeutic approaches selectively targeting apoptosis of malignant cell types while sparing normal keratinocytes in surrounding skin is desirable. Apo2Ligand/tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL) has been observed to preferentially induce cytopathic effects on transformed/malignant cell types compared with their non-neoplastic counterparts. In this report, two different biologically active preparations of Apo2L/TRAIL, a non-tagged version, NT-Apo2L/TRAIL, and a leucine zipper fusion protein, LZ-Apo2L/TRAIL, were examined for their ability to trigger apoptosis in normal human keratinocytes, and in an immortalized cell line (HaCaT cells). Differences between these preparations were observed, including: NT-Apo2L/TRAIL induced less keratinocyte apoptosis compared with LZ-Apo2L/TRAIL; NT-Apo2L/TRAIL also induced less apoptosis of HaCaT cells compared with LZ-Apo2L/TRAIL; LZ-Apo2L/TRAIL but not NT-Apo2L/TRAIL induced cytotoxic effects when keratinocytes became growth arrested due to undergoing spontaneous replicative senescence--a biological state previously observed to be resistant to UV-light-induced apoptosis. Similarities between preparations included: an enhanced ability for both Apo2L/TRAIL preparations to kill a greater relative percentage of HaCaT cells compared with keratinocytes; enhanced cytotoxicity towards keratinocytes that had their NF-B activity inhibited; a dependence of both Apo2L/TRAIL preparations on FADD and caspase activation; triggering of the same caspase cascades including caspase 8 and 3; and an ability to induce apoptosis even when HaCaT cells and keratinocytes were transduced to overexpress either Bcl-2 or Bcl-x(L) (survival factors that reduce susceptibility to UV-light-induced apoptosis). These results indicate that while both preparations of Apo2L/TRAIL possess biological activity, there are important differences as regards their ability to induce apoptosis in normal and immortalized keratinocytes. Moreover, the death receptor pathway triggered by LZ-Apo2L/TRAIL can overcome the apoptotic resistance normally observed in response to UV-light mediated by Bcl-2/Bcl-x(L), as well as by the state of cellular senescence. Unraveling the molecular basis for these differential biological effects may reveal a new strategic role for these death receptor/ligands linked to apoptosis in maintaining the dynamic balance of keratinocyte proliferation, differentiation, and cell death necessary to achieve a homeostatic thickness and function of normal skin. In addition, it may be possible to utilize these Apo2L/TRAIL preparations for the treatment of various sun-induced skin cancers as they can differentially trigger apoptosis of transformed keratinocytes, or keratinocytes with abnormal NF-kappaB signaling, while sparing adjacent normal keratinocytes.