Original Research: Different imiquimod creams resulting in differential effects for imiquimod-induced psoriatic mouse models

Short-chain fatty acids ameliorate imiquimod-induced skin thickening and IL-17 levels and alter gut microbiota in mice: a metagenomic association analysis

Short-chain fatty acids (SCFAs) have been proposed to have anti-inflammatory effects and improve immune homeostasis. We aimed to examine the effects of SCFAs on skin phenotype, systemic inflammation, and gut microbiota in mice with psoriasis-like inflammation. Imiquimod (IMQ)-treated C57BL/6 mice served as the study model. We conducted a metagenomic association study of IMQ-mice treated with SCFAs or anti-IL-17 antibody using whole-genome shotgun sequencing. The associations among SCFA supplements, skin thickness, circulating inflammatory profiles, and fecal microbiota profiles were investigated. The microbiome study was performed using pipelines for phylogenetic analysis, functional gene analysis, and pathway analysis. In IMQ-treated mice, there were increases in skin thickness and splenic weight, as well as unique fecal microbial profiles. SCFAs ameliorated IMQ-induced skin thickening, splenic weight gain, and serum IL-17F levels, with results that were comparable with those receiving anti-IL-17 treatment. IMQ-treated mice receiving SCFAs had greater microbial diversity than mice treated with IMQ alone. SCFAs and anti-IL17 treatment were associated with alteration of gut microbiota, with increased prevalences of Oscillospiraceae and Lachnopiraceae and decreased prevalences of Muribaculaceae and Bacteroides, which have been predicted to be associated with increased glycan degradation, phenylalanine metabolism, and xylene degradation. SCFAs may mitigate IMQ-induced skin thickening and IL-17F levels and alter fecal microbiota profiles in IMQ-treated mice.

Ameliorative effects of topical ramelteon on imiquimod-induced psoriasiform inflammation in mice

Psoriasis is a long-lasting, immune-related inflammatory skin disease that affects 2-3% of the global population. It is distinguished by erythematous, silvery, and scaly patches. Ramelteon is a type of melatonin agonist that is used to treat insomnia. It has enhanced non-classical immunomodulatory and anti-inflammatory activities. The aim of the study is to assess the ameliorative effects of topical ramelteon on imiquimod (IMQ)-aggravated psoriasiform-like dermatosis in mice. The 32 albino mouse males were placed into six groups of eight animals, all of them. With the exception of the control group, all groups gained a once-a-day regimen of topical imiquimod 5% cream at a dose of 62.5 mg for eight uninterrupted days, while mice in the control group gained vaseline-based ointment alternately. Immediately after an 8-day induction period in the imiquimod group, mice in the clobetasol and ramelteon treatment groups obtained a twice-daily regimen of topical clobetasol propionate 0.05% ointment and 0.1% ointment, respectively, for a further 8 days. This extends the total duration of the experimental study to 16 continuous days. The findings of our study found that ramelteon significantly mitigated the concentrations of inflammatory cytokines in the skin tissue, including interleukin (IL)-6, IL-17A, IL-23, tumor necrosis factor-α (TNF-α), and vascular endothelial growth factor (VEGF), as well as the scores associated with psoriatic lesions, including erythema, scaling, skin thickening, ear thickness, and overall cumulative PASI scores. Additionally, the anti-inflammatory impact of ramelteon was achieved by markedly increasing IL-10 levels in the skin tissue and correcting cutaneous histopathological alterations. Ramelteon ointment (0.1%) was comparable to that of clobetasol (0.05%) ointment in alleviating a mouse model of imiquimod-induced psoriasiform inflammation; this is probably due to its potential anti-inflammatory and immunomodulatory activities. Therefore, ramelteon could be a good additive option for therapeutic management of immune-triggered inflammatory conditions such as psoriasis.

An axon-T cell feedback loop enhances inflammation and axon degeneration

Inflammation is closely associated with many neurodegenerative disorders. Yet, whether inflammation causes, exacerbates, or responds to neurodegeneration has been challenging to define because the two processes are so closely linked. Here, we disentangle inflammation from the axon damage it causes by individually blocking cytotoxic T cell function and axon degeneration. We model inflammatory damage in mouse skin, a barrier tissue that, despite frequent inflammation, must maintain proper functioning of a dense array of axon terminals. We show that sympathetic axons modulate skin inflammation through release of norepinephrine, which suppresses activation of γδ T cells via the β2 adrenergic receptor. Strong inflammatory stimulation-modeled by application of the Toll-like receptor 7 agonist imiquimod-causes progressive γδ T cell-mediated, Sarm1-dependent loss of these immunosuppressive sympathetic axons. This removes a physiological brake on T cells, initiating a positive feedback loop of enhanced inflammation and further axon damage.

Nutraceutical combination ameliorates imiquimod-induced psoriasis in mice

Psoriasis is a chronic inflammatory skin disease that affects both localized and systemic regions of the body. This condition is characterized by the hyperproliferation of keratinocytes, resulting in skin thickening, scaling, and erythema. The severity of psoriasis depends on the extent of skin involvement, the location of the infection, and the symptoms that the person exhibits. While no cure exists, conventional therapies such as topical and systemic drugs are generally used to manage the exacerbation of symptoms. However, chronic use and overdose can lead to other severe adverse effects. Therefore, scientists and researchers are exploring potential nutraceuticals that can be considered as an alternative source of management for psoriasis. Current research aims to use different combinations of natural compounds like cannabidiol, myo-inositol, eicosapentaenoic acid, and krill oil to study the effect of these compounds in the prevention and treatment of psoriasis in the imiquimod (IMQ)-induced psoriatic mice model. The Psoriasis Area Severity Index (PASI) scoring system is used to analyze skin thickness, scales, and erythema. The results indicate that the krill oil combined with the cannabidiol and myo-inositol shows better results than other nutraceutical combinations. In the future, the natural products of krill oil can be combined with cannabidiol and myo-inositol to create an improved alternative to existing steroidal and nonsteroidal anti-inflammatory drugs for psoriasis treatment.

Tranexamic acid improves psoriasis-like skin inflammation: Evidence from in vivo and in vitro studies

The chronic disease psoriasis is associated with severe inflammation and abnormal keratinocyte propagation in the skin. Tranexamic acid (TXA), a plasmin inhibitor, is used to cure serious bleeding. We investigated whether TXA ointment mitigated Imiquimod (IMQ)-induced psoriasis-like inflammation. Furthermore, this study investigated the effect of noncytotoxic concentrations of TXA on IL-17-induced human keratinocyte (HaCaT) cells to determine the status of proliferative psoriatic keratinocytes. We found that TXA reduced IMQ-induced psoriasis-like erythema, thickness, scaling, and cumulative scores (erythema plus thickness plus scaling) on the back skin of BALB/c mice. Additionally, TXA decreased ear thickness and suppressed hyperkeratosis, hyperplasia, and inflammation of the ear epidermis in IMQ-induced BALB/c mice. Furthermore, TXA inhibited IMQ-induced splenomegaly in BALB/c mouse models. In IL-17-induced HaCaT cells, TXA inhibited ROS production and IL-8 secretion. Interestingly, TXA suppressed the IL-17-induced NFκB signaling pathway via IKK-mediated IκB degradation. TXA inhibited IL-17-induced activation of the NLRP3 inflammasome through caspase-1 and IL1β expression. TXA inhibited IL-17-induced NLRP3 inflammasome activation by enhancing autophagy, as indicated by LC3-II accumulation, p62/SQSTM1 expression, ATG4B inhibition, and Beclin-1/Bcl-2 dysregulation. Notably, TXA suppressed IL-17-induced Nrf2-mediated keratin 17 expression. N-acetylcysteine pretreatment reversed the effects of TXA on NFκB, NLRP3 inflammasomes, and the Nrf2-mediated keratin 17 pathway in IL-17-induced HaCaT cells. Results further confirmed that in the ear skin of IMQ-induced mice, psoriasis biomarkers such as NLRP3, IL1β, Nrf2, and keratin 17 expression were downregulated by TXA treatment. TXA improves IMQ-induced psoriasis-like inflammation in vivo and psoriatic keratinocytes in vitro. Tranexamic acid is a promising future treatment for psoriasis.

Dose-Response Efficacy and Mechanisms of Orally Administered Bifidobacterium breve CCFM683 on IMQ-Induced Psoriasis in Mice

This study aimed to investigate the dose-response effect of Bifidobacterium breve CCFM683 on relieving psoriasis and its underlying patterns. Specifically, the expression of keratin 16, keratin 17, and involucrin were substantially decreased by administration of 10⁹ CFU and 10¹⁰ CFU per day. Moreover, interleukin (IL)-17 and TNF-α levels were substantially decreased by 10⁹ and 10¹⁰ CFU/day. Furthermore, the gut microbiota in mice treated with 10⁹ or 10¹⁰ CFU/day was rebalanced by improving the diversity, regulating microbe interactions, increasing Lachnoclostridium, and decreasing Oscillibacter. Moreover, the concentrations of colonic bile acids were positively correlated with the effectiveness of the strain in relieving psoriasis. The gavage dose should be more than 10^8.42 CFU/day to improve psoriasis according to the dose-effect curve. In conclusion, CCFM683 supplementation alleviated psoriasis in a dose-dependent manner by recovering microbiota, promoting bile acid production, regulating the FXR/NF-κB pathway, diminishing proinflammatory cytokines, regulating keratinocytes, and maintaining the epidermal barrier function. These results may help guide probiotic product development and clinical trials in psoriasis.

Isostearic acid is an active component of imiquimod formulations used to induce psoriaform disease models

Topical imiquimod based creams are indicated as immune stimulants for papillomas and various skin neoplasms. Imiquimod is considered a TLR7 ligand. These creams are also used in research to induce skin inflammation in mice as a model for psoriasis. We observed that this inflammatory response was not strictly imiquimod dependent and we set out to establish which components drive the proinflammatory effects. To this end, we examined the induction response in a BALB/cJRj mouse model, in which 50 mg of cream is applied to 2 cm² of skin (125 mg/kg imiquimod-5% W/V, and/or 625 mg/kg isostearic acid-25% W/V). Comparing cream formulations containing isostearic acid, imiquimod and the combination, we observed that isostearic acid causes skin inflammation within 2 days, whereas imiquimod requires up to 5 days for initial signs. Isostearic acid activated an inflammasome response, stimulated release of proinflammatory cytokines and upregulated the IL-23/17 axis. Animals treated with isostearic acid had enlarged livers (+ 40% weight), which was not observed with imiquimod alone. Imiquimod was readily metabolized and cleared from plasma and liver, but was maintained at high levels in the skin throughout the body (200 mM at area of application; 200 µM in untreated skin). Imiquimod application was associated with splenomegaly, cytokine induction/release and initial body weight loss over 3 days. Despite high imiquimod skin levels throughout the animal, inflammation was only apparent in the treated areas and was less severe than in isostearic acid groups. As the concentrations in these areas are well above the 10 µM required for TLR7 responses in vitro, there is an implication that skin inflammation following imiquimod is due to effects other than TLR7 agonism (e.g., adenosine receptor agonism). In brain, isostearic caused no major changes in cytokine expression while imiquimod alone sightly stimulated expression of IL-1β and CCL9. However, the combination of both caused brain induction of CCL3, -9, CXCL10, -13, IL-1β and TNFα. The implication of these data is that isostearic acid facilitates the entry of imiquimod or peripherally secreted cytokines into the brain. Our data suggest that psoriaform skin responses in mice are more driven by isostearic acid, than generally reported and that the dose and route used in the model, leads to profound systemic effects, which may complicate the interpretation of drug effects in this model.

Indonesian Ciplukan Extract Inhibited TGF-β1/NF-κB Pathway in Experimental Psoriasis Mouse Models

Background:The global prevalence of psoriasis, a chronic inflammatory skin disease, has substantially increased in the last decade. The increase activity of Transforming Growth Factor ß1 (TGFß1)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway which cause inflammation, is the major pathological mechanism in psoriasis. Current psoriasis treatment using chemical agents is hampered by the side-effects when used long-term, which underlines the need for alternative, low side-effect anti-psoriatic agents. The extract of Physalis angulata L., also known as Ciplukan in Indonesia, contains Physalins, compounds known for their anti-inflammatory effects, but whose effect on psoriasis has not been studied. Objective:  This study aimed to investigate the effect of Ciplukan extract (CE) to TGFß1/NF-κB pathway in psoriasis mouse models. Methods: This was experimental study with posttest-only control group design. The CE active ingredients were identified using Liquid chromatography-tandem mass spectrometry (LC-MS/MS). Twenty-five female imiquimod (IMQ) induced psoriasis-like dermatitis mice were allocated into five groups, with three groups receiving 7 days of 400, 800, and 1200 mg/kg bodyweight doses of CE, respectively, and two groups serving as control and IMQ groups. The NF-κB and TGFß1 expressions were evaluated using Allred score based on immunohistochemistry (IHC) staining. Histopathology and clinical psoriasis manifestations were assessed using Baker’s from Hematoxylin Eosin (HE) staining and Psoriasis Area Severity Index (PASI) scores. The Kruskal-Wallis followed by Mann Whitney tests were conducted for data analysis. The p-value < 0.05 was considered to be statistically different.   Results: Based on LC-MS/MS test, Physalin B, D, and F were active ingredients from CE in ethyl acetate solution. An improvement in psoriasis inflammation was observed in 400 and 800 mg/kg bodyweight doses of CE, but only the dosage of 800 mg/kg BW significantly decreased of Allred scores from NF-κB and TGFß1 expressions; Baker’s and PASI scores compared to IMQ group (p<0.05). The 1200 mg/kg bodyweight doses of CE associated with acute toxicity signs and mortality, meanwhile dosage of 800 mg/kg BW showed the highest efficacy with lowest toxicity effect. Conclusions: Ciplukan extract improved psoriasis manifestations via inhibition effect to TGFß1/NF-κB pathway and the extract might be developed as an alternative anti-psoriasis agent

Evaluation of antipsoriatic activity of gel containing Pongamia pinnata extract on Imiquimod-induced psoriasis

Background

Pongamia pinnata (Fabaceae) is among those categories of plants mentioned in Ayurveda and traditionally known to use in several types of disease and disorders. The objective of the present work was to investigate the anti-psoriatic activity of Pongamia pinnata leaves extracts in Herbal gel formulation.

Results

Hydroalcoholic leaves extract of Pongamia pinnata was first subjected to phytochemical screening and quantification of phytoconstituents. Herbal gel was prepared containing Pongamia pinnata extracts using Carbopol 934 as gelling agent. The prepared gel formulations were studied for pH, viscosity, Spreadability and in vitro diffusion studies. The imiquimod-induced psoriatic mouse model, showed a prominent anti-psoriatic activity of the extract as evident through index grading. Treatment with extract confirmed a noteworthy reduction in psoriasis in the treated groups as there was a considerable diminution in the thickness and scaling of skin.

Conclusions

Lack of proper treatment and disadvantages associated with allopathic medicines pave the way to extensive research in natural products with anti-psoriatic activity. The present research scientifically justified the anti-psoriatic activity of the Hydroalcoholic extracts of Pongamia pinnata leaves.

A Localized Aldara (5% Imiquimod)-Induced Psoriasiform Dermatitis Model in Mice Using Finn Chambers

The expanding number of research studies utilizing the imiquimod-induced psoriasiform dermatitis model attests to the usefulness of this procedure. Advantages of this model include rapid development of the skin response and cost-effectiveness. A major limitation is that application of imiquimod cream over large areas of skin, as well as licking and ingestion of the cream, may lead to severe systemic inflammation, which can cause a general decline in health, splenomegaly, and death. In this protocol, Finn chambers are used to localize the imiquimod cream to a small area of the skin. This results in production of severe and reproducible psoriatic skin reactions with significantly less imiquimod, greatly reducing the possibility of untoward systemic effects. Moreover, having psoriasiform and control skin areas on the same mice decreases inter-animal differences. The protocol can be readily adapted for other skin disease models involving topical application of test agents. This article also details functional measurements performed during assays, including skin thickness, blood perfusion, semiquantitative histopathological evaluation, determination of scaling score to monitor psoriatic symptoms, and collection of spleen and body weight data to identify systemic effects. © 2020 The Authors. Basic Protocol: Use of Finn chambers to induce psoriasiform skin reactions with imiquimod Support Protocol 1: Measurement of double-fold dorsal skin thickness Support Protocol 2: Measurement of blood perfusion Support Protocol 3: Determination of scaling score Support Protocol 4: Semiquantitative histopathological scoring Support Protocol 5: Assessment of systemic side effects in response to imiquimod application.

Strain specific response of mice to IMQ-induced psoriasis

OBJECTIVES

Psoriasis is an autoimmune, inflammatory disease that needs a reliable animal model. Imiquimod (IMQ)-induced psoriasis is a widely used preclinical tool for psoriasis research. However, this model is sensitive to the genetic variation of mice. The present study explores mice's genetic background on disease stability and severity induced by IMQ.

METHODS

Three distinct strains of mice (Balb/c, C57BL/6, and Swiss albino) were divided into four groups (Vaseline, IMQ, IMQ+Clobetasol, and IMQ+Curcumin). Psoriasis area severity index (PASI) score, ear/back skin thickness, body weight alterations, and histopathological examination were employed to analyze disease severity. The spleen index studied the systemic effect. Strain effect on oxidative stress induced by IMQ was evaluated by estimating antioxidant factors, superoxide dismutase (SOD), catalase, and glutathione (GSH).

RESULTS

IMQ application resulted in increased PASI score, thickness, and alterations in body weight, confirming disease development in all the mice. However, the disease stability/severity between these strains was not identical. Although IMQ application caused splenomegaly, IMQ+curcumin treated C57BL/6 mice demonstrated a synergistic effect of IMQ and curcumin on the spleen resulting in increased splenomegaly. Decreased cellular enzyme activity in SOD, Catalase, and levels of GSH was observed in IMQ challenged mice, indicating the participation of the redox system in the genesis of the disease that was comparable among the strains.

CONCLUSIONS

These results indicate the existence of strain-dependent development of the disease. The Swiss model was found to be better in terms of disease severity and stability than other models. Further, a detailed mechanistic study might help to explain the pathological difference between these strains.

Imiquimod does not elicit inflammatory responses in the skin of the naked mole rat (Heterocephalus glaber)

Objective

Naked mole rat (Heterocephalus glaber) has recently attracted interest in biomedical research due to its exceptional longevity, cancer resistance and tolerance to potentially harmful conditions or stimuli. Given its unique attributes, this study was designed to characterize inflammatory skin reactions of this animal to topical application of imiquimod, a toll-like receptor 7 and 8 agonist that triggers psoriasis-like skin reaction.

Results

Imiquimod did not cause the expected psoriasis-like skin changes. There was no epidermal thickening and a straight epidermo-dermal boundary was maintained. There was no parakeratosis and the granular layer of epidermis was well formed. In the dermis, there was no leukocyte infiltration. This points to an exceptional nature of inflammatory/immune responses of this animal, but the mechanism could not be explained by our results. Naked mole rat could be a valuable negative model for studying psoriasis and other inflammatory skin conditions but as a prerequisite, there is need for further investigations to establish the mechanisms behind its lack of response to imiquimod.

LC/MS/MS analyses of open-flow microperfusion samples quantify eicosanoids in a rat model of skin inflammation

Eicosanoids are lipid-mediator molecules with key roles in inflammatory skin diseases, such as psoriasis. Eicosanoids are released close to the source of inflammation, where they elicit local pleiotropic effects and dysregulations. Monitoring inflammatory mediators directly in skin lesions could provide new insights and therapeutic possibilities. Here, we analyzed dermal interstitial fluid samples obtained by dermal open-flow microperfusion in a rat model of skin inflammation. We developed a solid-phase extraction ultra-HPLC/MS/MS method to reliably and precisely analyze small-volume samples and quantified 11 eicosanoids [thromboxane B2, prostaglandin (PG) E2, PGD2, PGF2α, leukotriene B4, 15-HETE, 12-HETE, 5-HETE, 12-hydroxyeicosapentaenoic acid, 13-HODE, and 17-hydroxydocosahexaenoic acid]. Our method achieved a median intraday precision of approximately 5% and interday precision of approximately 8%. All calibration curves showed excellent linearity between 0.01 and 50 ng/ml (R2 > 0.980). In the rat model, eicosanoids were significantly increased in imiquimod-treated inflamed skin sites compared with untreated control sites. Oral treatment with an anti-inflammatory glucocorticoid decreased eicosanoid concentrations. These results show that a combination of tissue-specific sampling with LC/MS analytics is well suited for analyzing small sample volumes from minimally invasive sampling methods such as open-flow microperfusion or microdialysis to study local inflammation and the effect of treatments in skin diseases.

Oral Administration of Vanillin Improves Imiquimod-Induced Psoriatic Skin Inflammation in Mice

Vanillin is one of the most widely used flavoring products worldwide. Psoriasis is a chronic inflammatory skin disorder. The interleukin-23 (IL-23)/interleukin-17 (IL-17) axis plays a critical role in psoriasis. Here, we analyzed the effect of vanillin on imiquimod (IMQ)-induced psoriatic skin inflammation in mice. Mice were treated topically with IMQ on the back skin and orally with various amounts of vanillin for 7 consecutive days. Vanillin significantly improved IMQ-induced histopathological changes of skin in a dose-dependent manner. The thickness and number of cell layers of epidermis were reduced by 29 ± 14.4 and 27.8 ± 11%, respectively, in mice given 100 mg/kg of vanillin. A microarray showed that a total of 9042 IMQ-upregulated genes were downregulated by vanillin, and the biological pathways involved in the immune system and metabolism were significantly altered by vanillin. The upregulated expressions of IL-23, IL-17A, and IL-17F genes were suppressed by vanillin, with fold changes of -3.07 ± 0.08, -2.06 ± 0.21, and -1.62 ± 0.21, respectively. Moreover, vanillin significantly decreased both the amounts of IL-17A and IL-23 and the infiltration of immune cells in the skin tissues of IMQ-treated mice. In conclusion, our findings suggested that vanillin was an effective bioactive compound against psoriatic skin inflammation. Moreover, the downregulation of IL-23 and IL-17 expression suggested that vanillin was a novel regulator of the IL-23/IL-17 axis.

BAY 11-7082 inhibits the NF-κB and NLRP3 inflammasome pathways and protects against IMQ-induced psoriasis

BAY 11-7082 antagonizes I-κB kinase-β preventing nuclear translocation of nuclear factor-κB (NF-κB); it also inhibits NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation. NF-κB is involved in psoriasis, whereas the role of NLRP3 is controversial. We investigated BAY 11-7082 effects in an experimental model of psoriasis-like dermatitis. Psoriasis-like lesions were induced by a topical application of imiquimod (IMQ) cream (62.5 mg/day) on the shaved back skin of C57BL/6 and NLRP3 knockout (KO) mice for 7 consecutive days. Sham psoriasis animals were challenged with Vaseline cream. Sham and IMQ animals were randomized to receive BAY 11-7082 (20 mg/kg/i.p.) or its vehicle (100 μl/i.p of 0.9% NaCl). Skin of IMQ animals developed erythema, scales, thickening and epidermal acanthosis. IMQ skin samples showed increased expression of pNF-κB and NLRP3 activation. BAY 11-7082 blunted epidermal thickness, acanthosis and inflammatory infiltrate. BAY 11-7082 reduced pNF-κB, NLRP3, tumour necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β expression, blunted the phosphorylation of signal transducer and activators of transcription 3 (STAT3) and decreased IL-23 levels. In addition, BAY 11-7082 reawakened the apoptotic machinery. NLRP3 KO animals showed a reduced total histological score but persistent mild acanthosis, dermal thickness and expression of pNF-κB and pSTAT3, following IMQ application. Our data suggest that BAY 11-7082 might represent an interesting approach for the management of psoriasis-like dermatitis depending on the dual inhibition of NF-κB and NLRP3.

The Snowballing Literature on Imiquimod-Induced Skin Inflammation in Mice: A Critical Appraisal

Since 2009, the imiquimod- or Aldara-induced (3M Pharmaceuticals, St. Paul, MN) model of acute skin inflammation has become the most widely used mouse model in preclinical psoriasis studies. Although this model offers researchers numerous benefits, there are important limitations and possible confounding variables to consider. The imiquimod model requires careful consideration and warrants scrutiny of the data generated by its use. In this perspective, we provide an overview of the advantages and disadvantages of this mouse model and offer suggestions for its use in psoriasis research.