Topical application of nonsteroidal anti-inflammatory drugs prevents vehicle-induced improvement of psoriasis

The role of xenobiotics in triggering psoriasis

Psoriasis is a common inflammatory skin disease affecting approximately 2% of the world population. A complex interplay of genetic predisposition and risk factors contributes to the risk of its onset. Several xenobiotics have been implicated in the pathogenesis of psoriasis. Drugs are among the most investigated trigger factors; strong association with disease induction or exacerbation has been reported for β-blockers, lithium, NSAIDs and ACE inhibitors, all of which are commonly used in the management of various comorbidities in psoriasis patients. Furthermore, inhibitors of TNF have a well-documented potential for triggering new-onset psoriasis when used for other indications (e.g. Crohn's disease or rheumatoid arthritis), while post-marketing data have revealed the same association for ustekinumab. Several other drugs have been connected with psoriasis, but the evidence is less compelling. Smoking and alcohol have been reported to increase the risk for occurrence of psoriasis, but can also affect unfavorably the course of the disease and its response to treatment. Furthermore, exposure to secondhand smoke, especially in childhood, also mediates the risk. Emerging data now suggest that air pollution also has a detrimental effect on skin disease, including psoriasis, but this association needs further investigation. Understanding of the toxic effect of xenobiotics on the initiation and clinical course of psoriasis can contribute to its better control, as it can help with the avoidance of triggering factors and, in some cases, influence the success of pharmacological treatment. It, therefore, has an important place in the comprehensive management of psoriasis.

Use of aspirin, non-steroidal anti-inflammatory drugs, and acetaminophen (paracetamol), and risk of psoriasis and psoriatic arthritis: a cohort study

Non-steroidal anti-inflammatory drugs (NSAIDs) have been reported to induce or exacerbate psoriasis. We aimed to evaluate the association between several widely used analgesics, including aspirin, non-aspirin NSAIDs, and acetaminophen (paracetamol), and risk of psoriasis and psoriatic arthritis (PsA) in a large cohort of US women, the Nurses' Health Study II (1991-2005). Information on regular use of aspirin, NSAIDs, and acetaminophen was collected for 95,540 participants during the follow-up. During 1,321,280 person-years of follow-up, we documented 646 incident psoriasis cases and 165 concomitant PsA cases. Compared to women who reported no use, regular acetaminophen and NSAIDs users with more than 10 years of use had multivariate hazard ratios of 3.60 [95% confidence interval (CI): 2.02-6.41] and 2.10 (95% CI: 1.11-3.96) for PsA, respectively. There was no clear association between aspirin and risk of psoriasis or PsA. In conclusion, long-term acetaminophen and NSAIDs use may be associated with an increased risk of PsA. Special attention on psoriasis and PsA screening may be needed for those who are prescribed for acetaminophen and NSAIDs for long-term periods.

Recent advances in the treatment of psoriatic arthritis

This article provides an overview of recent developments in the treatment of psoriatic arthritis with an emphasis on patent literature for the period January 1998 to December 2002. The main pathogenic pathways thought to be operative in psoriatic arthritis are highlighted and some novel compounds that can potentially interfere with such pathways at different levels are discussed. Among the new agents proposed, the inhibitors of cytokine signaling, angiogenesis, and extracellular matrix degradation appear to be of particular interest for the treatment of psoriatic arthritis resistant to conventional therapies. Finally, new formulations of existing drugs and natural remedies claimed to be useful for the treatment of psoriatic arthritis are reviewed.

Effects of topical antiinflammatory agents on Freund's adjuvant-induced skin lesions in rats

Freund's adjuvant, when administered intradermally to rats, causes polyarthritis as well as inflammation of the skin, eye, gastrointestinal and genitourinary tracts. We assessed the effects of antiinflammatory drugs on ear skin lesions to determine if this might be a useful skin inflammation model. The hind paw of male Lewis rats was injected with Mycobacterium butyricum in paraffin oil. Lesions appeared between days 13 and 15 after adjuvant injection. Each ear exhibited on average 1 to 3 highly erythematous, elevated lesions, 2 to 3 mm in diameter. By histology, the lesions consisted of epidermal hyperplasia, with a prominent accumulation of inflammatory cells in the dermis. Ears were treated topically with glucocorticoids, cyclosporine and indomethacin on days 15 through 21 after adjuvant injection. By day 22, dexamethasone, fluocinolone acetonide, and cyclosporine caused near-complete clearing of lesions whereas indomethacin exacerbated the inflammation by causing increased numbers of skin lesions. These results show the potential usefulness of adjuvant-induced skin lesions in rats as a novel subchronic inflammation model.

Prostaglandin E2 prevents diclofenac-induced enhancement of histamine release and inflammation evoked by in vivo challenge with compound 48/80 in the hamster cheek pouch

Based on observations obtained by the use of intravital microscopy, we report that prostaglandins (PGs) can exert inhibitory effects on mast cell-dependent inflammation. Thus, the PG-synthesis inhibitors diclofenac and indomethacin potentiated extravasation of plasma evoked by challenge with the mast cell secretagogue compound 48/80. Although the plasma leakage induced by compound 48/80 was in large mediated by histamine, neither diclofenac nor indomethacin potentiated the plasma leakage caused by exogenous histamine. These findings indicated that endogenous PGs inhibited the mast cell-dependent reaction at the level of mediator release. This mode of action was confirmed, as diclofenac was found to enhance the in vivo release of histamine that ensued challenge with compound 48/80. Moreover, the enhancement of the response to compound 48/80 observed after diclofenac treatment was prevented by local administration of PGE2 (30 nM). This inhibition included both the histamine release and the plasma leakage. In addition, diclofenac enhanced the leukocyte emigration after compound 48/80 challenge, and PGE2 reversed also this effect, suggesting that endogenous PGs (e.g. PGE2) also inhibited the release of chemotactic mediators.

Lack of effect of topical indomethacin on psoriasis

Topical 1% indomethacin had no effect on chronic stable plaque psoriasis in an open controlled study using subjective clinical scores nor in a randomised double-blind inert base controlled study using both subjective and objective measurements of lesional response; nor did it initiate or affect the development of psoriasis after cold injury. Previous studies are reviewed and it is concluded that the evidence does not support the hypothesis which relates psoriasis to eicosanoids produced by lipoxygenase activity.

Effects of two novel inhibitors of 5-lipoxygenase, L-651,392 and L-651,896, in a guinea-pig model of epidermal hyperproliferation

The effects of two novel and structurally different 5-lipoxygenase inhibitors, L-651,392 (4-bromo-2,7-dimethoxy-3H-phenothiazin-3-one) and L-651,896 (2,3-dihydro-6-(3-(2-hydroxymethyl)phenyl-2-propenyl)-5-benzo furanol), on epidermal proliferation were examined in the guinea-pig ear stimulated with the calcium ionophore A23187. Topical application of A23187 on the guinea-pig ear induced epidermal hyperproliferation which could be quantitated by tritiated-thymidine incorporation into DNA in the heat-separated epidermis. The ionophore-induced response was inhibited dose dependently by either L-651,392 or L-651,896 when the guinea-pigs were pretreated topically with these compounds. In separate experiments, it was demonstrated that A23187 induced a significant increase in the levels of immunoreactive-LTB4 in the guinea-pig ear which could be blocked by either inhibitors. It was suggested that L-651,392 and L-651,896 inhibited the ionophore-induced epidermal proliferation via their inhibitory action on the 5-lipoxygenase pathway of arachidonic acid metabolism.

Effects of oral meclofenamate therapy in psoriasis

One hundred three patients entered a study to evaluate the effects of oral meclofenamate sodium therapy on psoriasis. The first 4 weeks of the study were double-blind, with patients receiving either meclofenamate or placebo. Most patients receiving meclofenamate had no change in their psoriasis, in comparison with their pretherapy condition. There was no difference in the response of the psoriasis between the group taking meclofenamate and the group taking placebo. Eighty-nine patients continued in a 4-week open trial of meclofenamate. Approximately one third of the patients showed improvement, but this result appeared to be related to the open trial design. Since oral meclofenamate therapy was not associated with frequent worsening of psoriasis, it is an appropriate treatment for psoriatic arthritis.