Tumour necrosis factor-α plays a significant role in the Aldara-induced skin inflammation in mice.

BACKGROUND: Recently, the Aldara-induced psoriasis-like skin inflammation model in mice has attracted increased attention, due to its dependence on the same immunological pathways and cell types as in human psoriasis. OBJECTIVES: To study the impact of constitutive deficiency of tumour necrosis factor (TNF)-α and its upstream regulator mitogen-activated protein kinase-activated protein kinase 2 (MAPKAPK-2, herein MK2) in the Aldara-induced psoriasis-like skin inflammation model. METHODS: TNF-α knockout (KO), MK2 KO and wild-type (WT) mice divided into separate groups received either 45-mg Aldara cream or control cream for 5 consecutive days. The skin inflammation was evaluated clinically, histologically, and by quantitative reverse transcription-polymerase chain reaction. RESULTS: We found that TNF-α KO mice developed significantly less skin inflammation compared with WT mice, as evaluated clinically and histologically. At the molecular level, we demonstrated that the Aldara-induced mRNA expression of the psoriasis-related inflammatory markers interleukin (IL)-17C, IL-23p19, IL-12p40, IL-17A, IL-22 and S100A8 was significantly decreased in TNF-α KO mice compared with WT mice. No significant difference in the mRNA expression of these inflammatory markers between MK2 KO mice and WT mice was found, although Aldara-treated MK2 KO mice showed a tendency towards a lower mRNA expression of IL-17A and IL-22 compared with WT mice. CONCLUSIONS: We were able to demonstrate significantly lower levels of inflammation in TNF-α KO mice compared with WT mice, supporting the use of this model in future studies characterizing the role of TNF-α in psoriasis.

Changes in mRNA expression precede changes in microRNA expression in lesional psoriatic skin during treatment with adalimumab.

BACKGROUND: Tumour necrosis factor (TNF)-α inhibition is an effective treatment for moderate to severe plaque-type psoriasis. A change in the cytokine expression profile occurs in the skin after 4 days of treatment, preceding any clinical or histological improvements. MicroRNAs (miRNAs) are important post-transcriptional regulators of gene expression, but miRNA expression has never been studied in psoriatic skin during treatment. OBJECTIVE: To investigate changes in miRNA expression in psoriatic skin during adalimumab treatment and to compare results with changes in miRNA expression in a mouse model of Aldara-induced psoriasis-like skin inflammation. METHODS: Punch biopsies were obtained from nonlesional and lesional psoriatic skin during adalimumab treatment. In the mouse model of Aldara-induced skin inflammation, biopsies were obtained from TNF-α knockout (KO), IL-17A KO and wild-type mice. miRNA expression levels were analysed with microarray, reverse transcriptase quantitative polymerase chain reaction and in situ hybridization. RESULTS: In psoriatic skin, no changes in miRNA expression were seen 4 days after treatment initiation. After 14 days of treatment, the expression of several miRNAs was normalized towards the level seen in nonlesional skin before treatment. miR-23b expression increased after 14 days of treatment and remained high for 84 days, despite unaltered levels at baseline. In the mouse model of Aldara-induced skin inflammation, the level of miR-146a increased, whereas no regulation was seen for miR-203, miR-214-3p, miR-125a, miR-23b or let-7d-5p. CONCLUSIONS: This study demonstrates that the changes seen in the cytokine expression levels after 4 days of treatment with adalimumab are not facilitated by early changes in miRNA expression.

Aldara®-induced skin inflammation: studies of patients with psoriasis.

BACKGROUND: The application of Aldara(®) cream containing 5% imiquimod stimulates Toll-like receptor 7/8 on plasmacytoid dendritic cells, thereby producing a potent immunomodulatory effect. This has been reported to trigger psoriasis. OBJECTIVES: To establish a human model of Aldara-induced psoriasis-like skin inflammation in patients with psoriasis. METHODS: Nonlesional psoriatic skin of 13 patients was treated with Aldara for 2 or 7 days. The skin was evaluated clinically and histologically on days 2, 4 and 7. Cytokine expression in Aldara-treated, lesional and nonlesional psoriatic skin was compared using reverse-transcription quantitative polymerase chain reaction. RESULTS: Nine of the 10 patients receiving application of Aldara under occlusion for 2 days developed redness, induration and scaling. Histological analysis revealed focal parakeratosis, acanthosis and perivascular mononuclear infiltration. On days 4 and 7 both clinical and histological signs of inflammation subsided. Two of the three patients treated with Aldara for 7 days developed erosions leading to psoriasis on day 21. Cytokine markers of activation of the innate immune system [interferon-α, interferon regulatory factor-7 and interleukin (IL)-1ß] were equally expressed in lesional and Aldara-treated skin (n = 6). IL-6 and tumour necrosis factor-α were preferentially expressed in Aldara-treated skin. Adaptive immune system activation occurred only partially: IL-23p19 and IL-22 were similarly overexpressed in Aldara-treated and lesional psoriatic skin, but IL-17A and IL-12p40 were significantly underexpressed in Aldara-treated skin compared with lesional psoriatic skin. IL-10 was significantly overexpressed in Aldara-treated skin. CONCLUSIONS: We were able to induce psoriasis-like skin inflammation although typical psoriasis did not develop, possibly due to incomplete adaptive immune system recruitment and the powerful stimulation of IL-10 counter-regulation.

Preferential inhibition of the mRNA expression of p38 mitogen-activated protein kinase regulated cytokines in psoriatic skin by anti-TNFα therapy.

BACKGROUND: Anti-TNFα therapies are well established for severe psoriasis; however, their mechanism of action in disease resolution is not fully understood. p38 mitogen-activated protein kinase (MAPK) is a kinase known to play a key role in the pathogenesis of psoriasis. OBJECTIVES: To elucidate the early effects of adalimumab, a human monoclonal anti-TNFα antibody, on the expression of interleukins in psoriatic skin. PATIENTS AND METHODS: Biopsies from patients with psoriasis were examined before and after the start of adalimumab therapy. mRNA expression of cytokines were measured with quantitative polymerase chain reaction. p38 MAPK and signal transducer and activator of transcription 3 (STAT3) were analysed by Western blotting and immunofluorescence analyses, and IL-17A and IL-17C were examined with immunohistochemistry. RESULTS: The increased mRNA level of IL-1ß, IL-8, IL-17C and IL-20 in lesional psoriatic skin was already significantly reduced 4 days after the start of adalimumab treatment, i.e. before clinical and histological improvement was detectable. The mRNA expression of the Th17-derived cytokines IL-17A, IL-17F and IL-22 as well as the dendritic cell product IL-23/IL-12 (p40) were not significantly reduced until 2 weeks after the start of treatment, whereas the mRNA expression of IL-23 (p19) and the Th1 cytokines IFN-γ and IL-2 were reduced late in disease resolution. IL-1ß, IL-8 and IL-20 are all known to be regulated by p38 MAPK. IL-17C was produced by cultured human keratinocytes and this production was also mediated by a p38 MAPK dependent mechanism. Moreover, the early effects of adalimumab included the phosphorylation of p38 MAPK, but not STAT3 phosphorylation. CONCLUSIONS: This study indicates that an important mechanism of action of anti-TNFα therapy in psoriasis is a reduction in p38 MAPK phosphorylation and a subsequent decrease in the expression of p38 MAPK regulated genes.

Non-CAA angiopathies and their possible interactions with cerebral amyloid angiopathy.

Cerebral amyloid angiopathy (CAA) is one of the two most common cerebral arteriopathies seen in the brains of elderly patients. The other is arteriosclerosis (AS), historically considered a consequence of chronic hypertension and also described as lipohyalinosis (LH), a clinicopathologic association that is increasingly questioned. These and other less frequently encountered degeneralions of the cerebral microvasculature (CADASIL, Binswanger subcortical leukoencephalopathy) share the common feature of degeneration of the medial smooth muscle layer within arteriolar walls. This can be dramatic in CAA, in the course of which complete replacement of medial smooth muscle by fibrillar amyloid may occur. It is a less prominent feature of CADASIL and BSLE: in the latter condition, medial smooth muscle hyperplasia, possibly a response to some kind of injury, is a more dramatic finding. In some of these "angiomyopathies", fibrinoid necrosis of the arterial wall and microaneurvsm formation may lead to stroke, manifest as cerebral hemorrhage. With CADASIL and BSLE, ischemic brain injury is more common. In the case of CAA, upregulation of the Abeta-amyloid precursor protein occurs when arteriolar smooth muscle cells in culture are exposed to prolonged hypoxia, especially with reoxygenation. Injury to arteriolar smooth muscle cells may be one mechanism by which angiomyopathies progress and become symptomatic.