Melatonin facts: Melatonin lacks immuno-inflammation boosting capacities at the molecular and cellular levels.

Among the properties melatonin is claimed to possess, are the immuno-inflammation inductive capacities that would be responsible of some of the paramount of activities melatonin is reported to have in most of the human pathological conditions. In the present paper, we measured the effect of melatonin on established cellular models of immuno-inflammation, and found none. The discrepancies are discussed, especially because those properties are reported at pharmacological concentration (1 µM and beyond) at which the melatonin receptors are desensitized by internalization, leading to putative non-receptor-dependent mechanism of action.

Dermal fibroblasts are the key sensors of aseptic skin inflammation through interleukin 1 release by lesioned keratinocytes.

IL-1 plays a crucial role in triggering sterile inflammation following tissue injury. Although most studies associate IL-1 release by injured cells to the recruitment of neutrophils for tissue repair, the inflammatory cascade involves several molecular and cellular actors whose role remains to be specified. In the present study, we identified dermal fibroblasts among the IL-1R1-expressing skin cells as key sensors of IL-1 released by injured keratinocytes. After in vitro stimulation by recombinant cytokines or protein extracts of lysed keratinocytes containing high concentrations of IL-1, we show that dermal fibroblasts are by far the most IL-1-responsive cells compared to keratinocytes, melanocytes and endothelial cells. Fibroblasts have the property to respond to very low concentrations of IL-1 (from 10 fg/ml), even in the presence of 100-fold higher concentrations of IL-1RA, by increasing their expression of chemokines such as IL-8 for neutrophil recruitment. The capacity of IL-1-stimulated fibroblasts to attract neutrophils has been demonstrated both in vitro using cell migration assay and in vivo using a model of superficial epidermal lesion in IL-1R1-deficient mice which harbored reduced expression of inflammatory mediators and neutrophil skin infiltration. Together, our results shed a light on dermal fibroblasts as key relay cells in the chain of sterile inflammation induced after epidermal lesion.

Anti-inflammatory activity of CKC-containing cationic emulsion eye drop vehicles.

Purpose: Preservative-free cationic emulsion-based artificial tears (ATs) or drug vehicles are innovative eye drop formulations with tear film stabilization and drug delivery properties, and valuable in vivo anti-inflammatory and wound healing properties. These ATs have recently reached the market as ATs for the management of dry eye disease (DED) symptoms (i.e., Cationorm) or as a drug vehicle for cyclosporine (Ikervis). The aim of the present study was to explore the mechanism of action underlying the intrinsic anti-inflammatory and wound-healing efficacies harbored by the cationic emulsions of cetalkonium chloride (CE-CKC). Methods: The anti-inflammatory activity of two CE-CKC (0.002% and 0.005% CKC) emulsions was evaluated by assessing the expression of proinflammatory genes and the secretion of various markers in the following human cell types stressed by different agents: peripheral blood mononuclear cells (PBMCs; stimulation with anti-CD3/anti-CD28 or lipopolysaccharide (LPS)), CD4+ T lymphocytes (TCD4; stimulation with anti-CD3/anti-CD28), and a human corneal epithelial cell line (HCE-2; stimulation with LPS). The cells were incubated for 30 min with a 10% dilution of CE-CKC emulsions and then cultured without the emulsions for 24 h or 72 h in the presence of the various challenging agents. The supernatant was collected, and the secreted markers quantitated with flow cytometry or an enzyme-linked immunosorbent assay (ELISA). Gene expression of inflammatory markers was evaluated only in the PBMCs and HCE-2 cells stimulated with LPS. The in vitro protein kinase C (PKC) binding assay for IC50 determination was performed using standard procedures. Results: The CE-CKC emulsions decreased inflammatory gene expression in LPS-stimulated PBMCs (IFN-γ, IL-17A, CXCL-9, and TNFα) and LPS-stimulated HCE-2 cells (THBS1 and CCL2). Both CE-CKC emulsions inhibited the secretion of IL-17 (from anti-CD3/anti-CD28-stimulated TCD4), TNFα, IFN-γ, and IL-2 (from anti-CD3-/anti-CD28-stimulated PBMCs), and IL-6 and IL-8 (from LPS-stimulated HCE-2). The in vitro PKC binding assay revealed that CKC, the cationic agent, is a specific PKCα inhibitor. In addition, tyloxapol, another excipient, showed some anti-inflammatory activity on IL-6 and IL-8 in the LPS-stimulated HCE-2 cells. Conclusions: This study indicates that the CE-CKC emulsions are able to directly modulate the secretion and expression of proinflammatory cytokines and chemokines. The results also suggest that CKC and tyloxapol are pharmacologically active excipients with potentially beneficial effects in vivo. These data shed new light on the efficacy observed on the DED signs of these CE-CKC emulsions in clinical trials.