Exploring the roles of prostanoids, leukotriens, and dietary fatty acids in cutaneous inflammatory diseases: Insights from pharmacological and genetic approaches

Cutaneous granulomas: mechanisms, cellular interactions and therapeutic insights

Granulomas are specialized biologic defence mechanisms that form in response to infections by pathogens, foreign bodies or specific stimuli such as antimicrobials or fungi. These structures function to isolate foreign materials and pathogens that cannot be eliminated by immune cells, primarily through macrophage activity. In the skin, granulomas are a hallmark of several conditions, including sarcoidosis, granuloma annulare, tuberculosis and leprosy, each exhibiting distinct pathological and immunological features. Granulomas can also arise from lipid accumulation, as observed in xanthogranuloma, or be triggered by inflammatory processes associated with unidentified antigens. Among their cellular components, Langhans-type multinucleated giant cells play a pivotal role in granuloma structure and function, contributing to pathogen containment and tissue remodelling, although their precise mechanisms of action remain an area of active investigation. In addition to these giant cells, recent studies have identified triggering receptors expressed on myeloid cells 2 (TREM2)+ macrophages as key contributors to granuloma formation and maintenance. These macrophages are involved in extracellular degradation of foreign substances and play a role in adapting to the hypoxic and nutrient-poor microenvironment of granulomas through metabolic reprogramming, including the pentose phosphate pathway. Recent advances in molecular biology, such as single-cell RNA sequencing, have provided unprecedented insights into the cellular heterogeneity and molecular pathways involved in granuloma formation. These techniques have revealed disease-specific differences in immune cell profiles and activation states, offering new perspectives on the underlying mechanisms of granulomatous diseases. Despite these advances, the precise processes driving granuloma formation and their functional significance remain largely unclear. This review addresses the central question, 'What is a granuloma?', by synthesizing recent findings, with a particular focus on cutaneous granulomas, and presenting interpretations grounded in the current body of literature. We also discuss the implications of these findings for the development of novel therapeutic strategies, including targeted immunomodulation and cytokine blockade, which hold promise for treating granulomatous diseases while preserving host defence.

Bioactive lipids in the skin barrier mediate its functionality in health and disease

Our skin protects us from external threats including ultraviolet radiation, pathogens and chemicals, and prevents excessive trans-epidermal water loss. These varied activities are reliant on a vast array of lipids, many of which are unique to skin, and that support physical, microbiological and immunological barriers. The cutaneous physical barrier is dependent on a specific lipid matrix that surrounds terminally-differentiated keratinocytes in the stratum corneum. Sebum- and keratinocyte-derived lipids cover the skin's surface and support and regulate the skin microbiota. Meanwhile, lipids signal between resident and infiltrating cutaneous immune cells, driving inflammation and its resolution in response to pathogens and other threats. Lipids of particular importance include ceramides, which are crucial for stratum corneum lipid matrix formation and therefore physical barrier functionality, fatty acids, which contribute to the acidic pH of the skin surface and regulate the microbiota, as well as the stratum corneum lipid matrix, and bioactive metabolites of these fatty acids, involved in cell signalling, inflammation, and numerous other cutaneous processes. These diverse and complex lipids maintain homeostasis in healthy skin, and are implicated in many cutaneous diseases, as well as unrelated systemic conditions with skin manifestations, and processes such as ageing. Lipids also contribute to the gut-skin axis, signalling between the two barrier sites. Therefore, skin lipids provide a valuable resource for exploration of healthy cutaneous processes, local and systemic disease development and progression, and accessible biomarker discovery for systemic disease, as well as an opportunity to fully understand the relationship between the host and the skin microbiota. Investigation of skin lipids could provide diagnostic and prognostic biomarkers, and help identify new targets for interventions. Development and improvement of existing in vitro and in silico approaches to explore the cutaneous lipidome, as well as advances in skin lipidomics technologies, will facilitate ongoing progress in skin lipid research.

Causality of unsaturated fatty acids and psoriasis a Mendelian randomization study

Background

Many observational studies have identified a link between unsaturated fatty acids and psoriasis. However, they contain reverse causality and confounding factors, and there is no definite causal study between unsaturated fatty acids and psoriasis.

Objectives

Analysis of causality between unsaturated fatty acids and psoriasis by Mendelian randomization.

Methods

We used IEU Open GWAS Project, omega-3 PUFA and omega-6 PUFA data from 114,999 subjects, MUFA data from 13,535 subjects, and psoriasis data from 4,510 cases and 212,242 controls were included. We employed the inverse-variance weighted (IVW) method as the primary analytical approach and four additional MR methods. Moreover, we performed heterogeneity and horizontal pleiotropy assessments using Cochrane's Q and MR-Egger intercept tests, respectively. Finally, we performed sensitivity analyses to enhance our findings' precision and veracity.

Results

IVW results showed no causal effect of omega-3 PUFA on psoriasis (p = 0.334; OR, 0.909; 95% CI, 0.748-1.104), omega-6 PUFA cause psoriasis (p = 0.046; OR, 1.174; 95% CI, 1.003-1.374), MUFA cause psoriasis (p = 0.032; OR, 1.218; 95% CI, 1.018-1.457), no causal effect of omega-3 PUFA in psoriasis (p = 0.695; OR, 0.989; 95% CI, 0.937-1.044), no causal effect of omega-6 PUFA in psoriasis (p = 0.643; OR, 1.013; 95% CI, 0.960-1.068), psoriasis is not causal to MUFA (p = 0.986; OR, 1.000; 95% CI, 0.949-1.055). Heterogeneity, horizontal pleiotropy, and sensitivity analyses showed reliable results.

Conclusion

We found that circulating omega-6 PUFA and MUFA cause psoriasis, while omega-3 PUFA do not. Treatments that lower circulating omega-6 PUFA and MUFA are effective in psoriasis. After a better understanding of fatty acid intake and circulation, the population can be advised to regulate their diet.

A Review of the Effects of Some Extrinsic Factors on Mice Used in Research

Animals have been used in research for over 2,000 y. From very crude experiments conducted by ancient scholars, animal research, as a science, was refined over hundreds of years to what we know it as today. However, the housing conditions of animals used for research did not improve significantly until less than 100 years ago when guidelines for housing research animals were first published. In addition, it was not until relatively recently that some extrinsic factors were recognized as a research variable, even when animals were housed under recommended guidelines. For example, temperature, humidity, light, noise, vibration, diet, water, caging, bedding, etc., can all potentially affect research using mice, contributing the inability of others to reproduce published findings. Consequently, these external factors should be carefully considered in the design, planning, and execution of animal experiments. In addition, as recommended by others, the housing and husbandry conditions of the animals should be described in detail in publications resulting from animal research to improve study reproducibility. Here, we briefly review some common, and less common, external factors that affect research in one of the most popular animal models, the mouse.

Combinative effects of akarkara root-derived metabolites on anti-inflammatory and anti-alzheimer key enzymes: integrating bioassay-guided fractionation, GC-MS analysis, and in silico studies

BACKGROUND

Anacyclus pyrethrum L. (Akarkara root), a valuable Ayurvedic remedy, is reported to exhibit various pharmacological activities. Akarkara root was subjected to bioassay-guided fractionation, to isolate its active constituents and discover their potential bioactivities, followed by computational analysis.

METHODS

The methanol extract and its fractions, methylene chloride, and butanol, were assessed for their antioxidant, anti-inflammatory, and anticholinergic potentials. The antioxidant activity was determined using DPPH, ABTS, FRAP, and ORAC assays. The in vitro anticholinergic effect was evaluated via acetyl- and butyryl-cholinesterase inhibition, while anti-inflammatory effect weas determined using COX-2 and 5-LOX inhibitory assays. The methylene chloride fraction was subjected to GC/MS analysis and chromatographic fractionation to isolate its major compounds. The inhibitory effect on iNOS and various inflammatory mediators in LPS-activated RAW 264.7 macrophages was investigated. In silico computational analyses (molecular docking, ADME, BBB permeability prediction, and molecular dynamics) were performed.

RESULTS

Forty-one compounds were identified and quantified and the major compounds, namely, oleamide (A1), stigmasterol (A2), 2E,4E-deca-2,4-dienoic acid 2-phenylethyl amide (A3), and pellitorine (A4) were isolated from the methylene chloride fraction, the most active in all assays. All compounds showed significant in vitro antioxidant, anticholinergic and anti-inflammatory effects. They inhibited the secretion of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in activated RAW macrophages. The isolated compounds showed good fitting in the active sites of acetylcholinesterase and COX-2 with high docking scores. The ADME study revealed proper pharmacokinetics and drug likeness properties for the isolated compounds. The isolated compounds demonstrated high ability to cross the BBB and penetrate the CNS with values ranging from 1.596 to -1.651 in comparison with Donepezil (-1.464). Molecular dynamics simulation revealed stable conformations and binding patterns of the isolated compounds with the active sites of COX-2 and acetyl cholinesterase.

CONCLUSIONS

Ultimately, our results specify Akarkara compounds as promising candidates for the treatment of inflammatory and neurodegenerative diseases.