Impact of Adalimumab Treatment on Interleukin-17 and Interleukin-17 Receptor Expression in Skin and Synovium of Psoriatic Arthritis Patients with Mild Psoriasis.

Interleukin (IL)-17 and tumor necrosis factor-alpha (TNF)-α are key players in psoriatic arthritis (PsA) pathogenesis. While both cytokines can be therapeutically targeted with beneficial clinical outcome, it is unclear whether inhibiting one cytokine will affect the other at sites of inflammation. If both act independently, this might provide a rationale for dual or combined inhibition of both cytokines. Here, we evaluated the effect of TNF blockade in PsA patients on IL-17 levels in both skin and synovial tissue biopsies. PsA patients with mild psoriatic skin lesions were randomized to receive either adalimumab or placebo for four weeks. Synovial and skin biopsies were obtained at weeks zero and four. Skin from healthy donors (HDs) was used for comparison. Expression of IL-17A, IL-17F, IL-17RA and IL-17RC was assessed by immunohistochemistry and analyzed with digital image analysis. We found relatively low levels of IL-17 and its receptors in the skin of PsA patients compared to HD, and only IL-17F in the dermis of lesional psoriatic skin was significantly higher compared to HD skin (p = 0.0002). Histologically IL-17A, IL-17F, IL-17RA and IL-17RC in skin and synovial tissue were not downregulated by adalimumab treatment. Thus, in this cohort of PsA patients with mild psoriasis, TNF blockade did not affect the protein levels of IL-17 cytokines and its receptors in skin and synovium, despite reduced cellular inflammation and improved clinical outcome for joint involvement.

Heterogeneous expression pattern of interleukin 17A (IL-17A), IL-17F and their receptors in synovium of rheumatoid arthritis, psoriatic arthritis and osteoarthritis: possible explanation for nonresponse to anti-IL-17 therapy?

INTRODUCTION: Accumulating evidence suggests an important role for interleukin 17 (IL-17) in the pathogenesis of several inflammatory diseases, including rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Accordingly, clinical trials aimed at blocking IL-17 have been initiated, but clinical results between patients and across different diseases have been highly variable. The objective was to determine the variability in expression of IL-17A, IL-17F and their receptors IL-17RA and IL-17RC in the synovia of patients with arthritis. METHODS: Synovial biopsies were obtained from patients with RA (n = 11), PsA (n = 15) and inflammatory osteoarthritis (OA, n = 14). For comparison, synovia from noninflamed knee joints (n = 7) obtained from controls were included. Frozen sections were stained for IL-17A, IL-17F, IL-17RA and IL-17RC and evaluated by digital image analysis. We used confocal microscopy to determine which cells in the synovium express IL-17A and IL-17F, double-staining with CD4, CD8, CD15, CD68, CD163, CD31, von Willebrand factor, peripheral lymph node address in, lymphatic vessel endothelial hyaluronan receptor 1, mast cell tryptase and retinoic acid receptor-related orphan receptor γt (RORγt). RESULTS: IL-17A, IL-17F, IL-17RA and IL-17RC were abundantly expressed in synovial tissues of all patient groups. Whereas IL-17RA was present mostly in the synovial sublining, IL-17RC was abundantly expressed in the intimal lining layer. Digital image analysis showed a significant (P < 0.05) increase of only IL-17A in arthritis patients compared to noninflamed control tissues. The expression of IL-17A, IL-17F and their receptors was similar in the different patient groups, but highly variable between individual patients. CD4+ and CD8+ cells coexpressed IL-17A, and few cells coexpressed IL-17F. IL-17A and IL-17F were not expressed by CD15+ neutrophils. Mast cells were only occasionally positive for IL-17A or IL-17F. Interestingly, IL-17A and IL-17F staining was also observed in macrophages, as well as in blood vessels and lymphatics. This staining probably reflects receptor-bound cytokine staining. Many infiltrated cells were positive for the transcription factor RORγt. Colocalisation between RORγt and IL-17A and IL-17F indicates local IL-17 production. CONCLUSIONS: Increased expression of IL-17A is not restricted to synovial tissues of RA and PsA patients; it is also observed in inflammatory OA. The heterogeneous expression levels may explain nonresponse to anti-IL-17 therapy in subsets of patients.

Effect of synthetic vernix biofilms on barrier recovery of damaged mouse skin.

The aim of this work was to investigate whether topical application of synthetic biofilms supports and accelerates the recovery of the murine skin barrier, disrupted by sequential tape stripping. Therefore, various biofilms were applied topically on disrupted mouse skin to determine which formulation could improve barrier function, as was observed previously for the natural biofilm vernix caseosa (VC). The biofilms [i.e. particles (synthetic corneocytes) embedded in a synthetic lipid matrix] mimic closely the physicochemical properties and structure of VC. Various formulations were prepared using different particle:lipid ratios, particles with different initial water content and uncoated or lipid-coated particles. It was observed that application of all tested formulations improved the skin barrier recovery rate and reduced crust formation and epidermal hyperproliferation. However, only one of the biofilms [i.e. B1; composed of uncoated particles with 50% (w/w) initial water content and particle:lipid ratio of 2:1] mimicked the effects of native VC most closely. This indicates the importance of the presence of individual components, i.e. barrier lipids and water, as well as the ratio of these components. Consequently, these observations suggest the potential use of this biofilm treatment clinically.

Development of a murine model to evaluate the effect of vernix caseosa on skin barrier recovery.

The aim of this study was twofold, that is the generation of a reliable model for skin barrier disruption and repair and to evaluate recovery of damaged skin after application of vernix caseosa (VC). VC was selected as its wound healing properties were suggested previously, but never clearly demonstrated. Five different levels of barrier disruption in mice, accomplished by tape-stripping, were evaluated. Disruption models such as moderate, severe #1 and #2 (transepidermal water loss (TEWL) of 31 +/- 2, 59 +/- 4 and 66 +/- 3 g/m(2)/h, respectively) showed complete recovery within 72 h. However, not all corneocytes were removed after tape-stripping. Additionally, models such as severe #3 and #4 (TEWL of 73 +/- 5 and 79 +/- 6 g/m(2)/h, respectively) with a more severe disruption were evaluated. After tape-stripping, all corneocytes were removed and the remaining epidermis was intact. However, model #3 still showed complete recovery within 72 h. With model #4, a crust was formed and almost complete recovery (approximately 90%) was obtained within only 8 days. The effect of VC application on recovery of disrupted skin was evaluated with model #3 and #4. Model #3 showed that application of VC predominantly influenced initial recovery and is therefore merely appropriate to study the effect of formulations in the initial recovery period. Topical application of VC on model #4 considerably increased initial and long-term recovery. Moreover, VC application promoted rapid formation of stratum corneum and prevented epidermal thickening. These observations not only confirm the ability of VC to enhance barrier recovery, but also suggest potential use of this treatment clinically.

Mast cell degranulation during abdominal surgery initiates postoperative ileus in mice.

BACKGROUND & AIMS: Inflammation of the intestinal muscularis following manipulation during surgery plays a crucial role in the pathogenesis of postoperative ileus. Here, we evaluate the role of mast cell activation in the recruitment of infiltrates in a murine model. METHODS: Twenty-four hours after control laparotomy or intestinal manipulation, gastric emptying was determined. Mast cell degranulation was determined by measurement of mast cell protease-I in peritoneal fluid. Intestinal inflammation was assessed by determination of tissue myeloperoxidase activity and histochemical staining. RESULTS: Intestinal manipulation elicited a significant increase in mast cell protease-I levels in peritoneal fluid and resulted in recruitment of inflammatory infiltrates to the intestinal muscularis. This infiltrate was associated with a delay in gastric emptying 24 hours after surgery. Pretreatment with mast cell stabilizers ketotifen (1 mg/kg, p.o.) or doxantrazole (5 mg/kg, i.p.) prevented both manipulation-induced inflammation and gastroparesis. Reciprocally, in vivo exposure of an ileal loop to the mast cell secretagogue compound 48/80 (0.2 mg/mL for 1 minute) induced muscular inflammation and delayed gastric emptying. The manipulation-induced inflammation was dependent on the presence of mast cells because intestinal manipulation in mast cell-deficient Kit/Kitv mice did not elicit significant leukocyte recruitment. Reconstitution of Kit/Kitv mice with cultured bone marrow-derived mast cells from congenic wild types restored the manipulation-induced inflammation. CONCLUSIONS: Our results show that degranulation of connective tissue mast cells is a key event for the establishment of the intestinal infiltrate that mediates postoperative ileus following abdominal surgery.