IL-1 and IL-36 are dominant cytokines in generalized pustular psoriasis.

BACKGROUND: Generalized pustular psoriasis (GPP) is a rare, debilitating, and often life-threatening inflammatory disease characterized by episodic infiltration of neutrophils into the skin, pustule development, and systemic inflammation, which can manifest in the presence or absence of chronic plaque psoriasis (PV). Current treatments are unsatisfactory and warrant a better understanding of GPP pathogenesis. OBJECTIVE: We sought to understand better the disease mechanism of GPP to allow improved targeted therapies. METHODS: We performed a gene expression study on formalin-fixed paraffin-embedded GPP (n = 28) and PV (n = 12) lesional biopsies and healthy control (n = 20) skin. Differential gene expression was analyzed using gene ontology and enrichment analysis. Gene expression was validated with quantitative RT-PCR and immunohistochemistry, and a potential disease mechanism was investigated using primary human cell culture. RESULTS: Compared with healthy skin, GPP lesions yielded 479 and PV 854 differentially expressed genes, respectively, with 184 upregulated in both diseases. We detected significant contributions of IL-17A, TNF, IL-1, IL-36, and interferons in both diseases; although GPP lesions furnished higher IL-1 and IL-36 and lower IL-17A and IFN-γ mRNA expression than PV lesions did. We detected prominent IL-36 expression by keratinocytes proximal to neutrophilic pustules, and we show that both neutrophils and neutrophil proteases activate IL-36. Suggesting another mechanism regulating IL-36 activity, the protease inhibitors serpin A1 and A3, which inhibit elastase and cathepsin G, respectively, were upregulated in both diseases and inhibited activation of IL-36. CONCLUSIONS: Our data indicate sustained activation of IL-1 and IL-36 in GPP, inducing neutrophil chemokine expression, infiltration, and pustule formation, suggesting that the IL-1/IL-36 inflammatory axis is a potent driver of disease pathology in GPP.

Anti-TNFα alters the natural history of experimental Crohn's disease in rats when begun early, but not late, in disease.

Anti-TNFα therapy decreases inflammation in Crohn's disease (CD). However, its ability to decrease fibrosis and alter the natural history of CD is not established. Anti-TNF-α prevents inflammation and fibrosis in the peptidoglycan-polysaccharide (PG-PS) model of CD. Here we studied anti-TNF-α in a treatment paradigm. PG-PS or human serum albumin (HSA; control) was injected into bowel wall of anesthetized Lewis rats at laparotomy. Mouse anti-mouse TNF-α or vehicle treatment was begun day (d)1, d7, or d14 postlaparotomy. Rats were euthanized d21-23. Gross abdominal and histologic findings were scored. Cecal levels of relevant mRNAs were measured by quantitative real-time PCR. There was a stepwise loss of responsiveness when anti-TNFα was begun on d7 and d14 compared with d1 that was seen in the percent decrease in the median gross abdominal score and histologic inflammation score in PG-PS-injected rats [as %decrease; gross abdominal score: d1 = 75% (P = 0.003), d7 = 57% (P = 0.18), d14 = no change (P = 0.99); histologic inflammation: d1 = 57% (P = 0.006), d7 = 50% (P = 0.019), d14 = no change (P = 0.99)]. This was also reflected in changes in IL-1ß, IL-6, TNF-α, IGF-I, TGF-ß1, procollagen I, and procollagen III mRNAs that were decreased or trended downward in PG-PS-injected animals given anti-TNF-α beginning d1 or d7 compared with vehicle-treated rats; there was no effect if anti-TNF-α was begun d14. This change in responsiveness to anti-TNFα therapy was coincident with a major shift in the cytokine milieu observed on d14 in the PG-PS injected rats (vehicle treated). Our data are consistent with the clinical observation that improved outcomes occur when anti-TNF-α therapy is initiated early in the course of CD.

The small molecule rhodomyrtone suppresses TNF-α and IL-17A-induced keratinocyte inflammatory responses: A potential new therapeutic for psoriasis.

Psoriasis is a common skin disease pathogenically driven by TNF and IL-17A-induced epidermal hyperproliferation and inflammatory responses. The ongoing need for new therapeutic agents for psoriasis has highlighted medicinal plants as sources of phytochemicals useful for treating psoriatic disease. Rhodomyrtone, a bioactive phytochemical from Rhodomyrtus tomentosa, has well-established anti-proliferative activities. This study assessed the potential of rhodomyrtone for curtailing TNF/IL-17A-driven inflammation. Stimulating human skin organ cultures with TNF+IL-17A to model the skin inflammation in psoriasis, we found that rhodomyrtone significantly decreased inflammatory gene expression and the expression and secretion of inflammatory proteins, assessed by qRT-PCR, immunohistochemistry and ELISA assays respectively. RNA-seq analysis of monolayer primary keratinocytes treated with IL-17A/TNF showed that rhodomyrtone inhibited 724/1587 transcripts >2-fold altered by IL-17A/TNF (p<0.01), a number of which were confirmed at the mRNA and protein level. Suggesting that rhodomyrtone acts by modulating MAP kinase and NF-κB signaling pathways, rhodomyrtone inhibited TNF-induced ERK, JNK, p38, and NF-κBp65 phosphorylation. Finally, assessing the in vivo anti-inflammatory potential of rhodomyrtone, we examined its effects on imiquimod-induced skin inflammation in mice, finding rhodomyrtone reversed imiquimod-induced skin hyperplasia and epidermal thickening (p< 0.001). Taken together, these results suggest that rhodomyrtone may be useful in preventing or slowing the progression of inflammatory skin disease.

Development of a peptidoglycan-polysaccharide murine model of Crohn's disease: effect of genetic background.

The peptidoglycan-polysaccharide (PGPS) model using inbred rats closely mimics Crohn's disease. Our aim was to identify mouse strains that develop ileocolitis in response to bowel wall injection with PGPS. Mouse strains studied included NOD2 knockout animals, RICK/RIP2 knockout animals, and genetically inbred strains that are susceptible to inflammation. Mice underwent laparotomy with intramural injection of PGPS or human serum albumin in the terminal ileum, ileal Peyer's patches, and cecum. Gross abdominal score, cecal histologic score, and levels of pro-fibrotic factor mRNAs were determined 20 to 32 days after laparotomy. PGPS-injected wild-type and knockout mice with mutations in the NOD2 pathway had higher abdominal scores than human serum albumin-injected mice. The RICK knockout animals tended to have higher mean abdominal scores than the NOD2 knockout animals, but the differences were not significant. CBA/J mice were shown to have the most robust response to PGPS, demonstrating consistently higher abdominal scores than other strains. Animals killed on day 26 had an average gross abdominal score of 6.1 ± 1.5, compared with those on day 20 (3.0 ± 0.0) or day 32 (2.8 ± 0.9). PGPS-injected CBA/J mice studied 26 days after laparotomy developed the most robust inflammation and most closely mimicked the PGPS rat model and human Crohn's disease.

Anti-tumor necrosis factor α prevents bowel fibrosis assessed by messenger RNA, histology, and magnetization transfer MRI in rats with Crohn's disease.

OBJECTIVE: Treatment of Crohn's disease (CD) with anti-tumor necrosis factor α (TNFα) decreases intestinal inflammation, but the effect on fibrosis remains unclear. We hypothesized that treatment with rat-specific anti-TNFα will decrease the development of intestinal fibrosis in a rat model of CD. We further hypothesized that magnetization transfer magnetic resonance imaging (MT-MRI) will be sensitive in detecting these differences in collagen content. METHODS: Rats were injected in the distal ileum and cecum with peptidoglycan-polysaccharide (PG-PS) or human serum albumin (control) at laparotomy and then received intraperitoneal injections of rat-specific anti-TNFα or vehicle daily for 21 days after laparotomy. Rats underwent MT-MRI abdominal imaging on day 19 or 20. MT ratio was calculated in the cecal wall. Cecal tissue histologic inflammation was scored. Cecal tissue procollagen, cytokine, and growth factor messenger RNAs were measured by quantitative real-time PCR. RESULTS: PG-PS-injected rats treated with anti-TNFα had less histologic inflammation, and cecal tissue expressed lower levels of proinflammatory cytokine messenger RNAs than vehicle-treated PG-PS-injected rats (IL-1ß: 5.59 ± 1.53 versus 10.41 ± 1.78, P = 0.02; IL-6: 23.23 ± 9.33 versus 45.89 ± 11.79, P = 0.07). PG-PS-injected rats treated with anti-TNFα developed less intestinal fibrosis than vehicle-treated PG-PS-injected rats by tissue procollagen I (2.87 ± 0.66 versus 9.28 ± 1.11; P = 0.00002), procollagen III (2.25 ± 0.35 versus 7.28 ± 0.76; P = 0.0000009), and MT-MRI (MT ratio: 17.79 ± 1.61 versus 27.95 ± 1.75; P = 0.0001). Insulin-like growth factor I (2.52 ± 0.44 versus 5.14 ± 0.60; P = 0.0007) and transforming growth factor ß1 (2.34 ± 0.29 versus 3.45 ± 0.29; P = 0.006) were also decreased in anti-TNFα-treated PG-PS-injected rats. CONCLUSIONS: Anti-TNFα prevents the development of bowel wall inflammation and fibrosis in the PG-PS rat model of CD. MT-MRI measurably demonstrates this decrease in intestinal fibrosis.

Resveratrol has antiinflammatory and antifibrotic effects in the peptidoglycan-polysaccharide rat model of Crohn's disease.

BACKGROUND: Resveratrol has antiinflammatory and antifibrotic effects. Resveratrol decreases proliferation and collagen synthesis by intestinal smooth muscle cells. We hypothesized that resveratrol would decrease inflammation and fibrosis in an animal model of Crohn's disease. METHODS: Peptidoglycan-polysaccharide (PG-PS) or human serum albumin (HSA) was injected into the bowel wall of Lewis rats at laparotomy. Resveratrol or vehicle was administered daily by gavage 1-27 days postinjection. On day 28, gross abdominal and histologic findings were scored. Cecal collagen content was measured by colorimetric analysis of digital images of trichrome-stained sections. Cecal levels of procollagen, cytokine, and growth factor mRNAs were determined. RESULTS: PG-PS-injected rats (vehicle-treated) developed more fibrosis than HSA-injected rats by all measurements: gross abdominal score (P < 0.001), cecal collagen content (P = 0.04), and procollagen I and III mRNAs (P ≤ 0.0007). PG-PS-injected rats treated with 40 mg/kg resveratrol showed a trend toward decreased gross abdominal score, inflammatory cytokine mRNAs, and procollagen mRNAs. PG-PS-injected rats treated with 100 mg/kg resveratrol had lower inflammatory cytokine mRNAs (IL-1ß [3.50 ± 1.08 vs. 10.79 ± 1.88, P = 0.005], IL-6 [17.11 ± 9.22 vs. 45.64 ± 8.83, P = 0.03], tumor necrosis factor alpha (TNF-α) [0.80 ± 0.14 vs. 1.89 ± 0.22, P = 0.002]), transforming growth factor beta 1 (TGF-ß1) mRNA (2.24 ± 0.37 vs. 4.06 ± 0.58, P = 0.01), and histologic fibrosis score (6.4 ± 1.1 vs. 9.8 ± 1.0; P = 0.035) than those treated with vehicle. There were trends toward decreased gross abdominal score and decreased cecal collagen content. Procollagen I, procollagen III, and IGF-I mRNAs also trended downward. CONCLUSIONS: Resveratrol decreases inflammatory cytokines and TGF-ß1 in the PG-PS model of Crohn's disease and demonstrates a promising trend in decreasing tissue fibrosis. These findings may have therapeutic applications in inflammatory bowel disease.