Background: Mechanisms causing the onset and perpetuation of inflammation in severe allergic patients remain unknown. Our previous studies suggested that severe allergic inflammation is linked to platelet dysfunction. Methods:Platelet-rich plasma (PRP) and platelet-poor plasma (PPP) samples were obtained by platelet-apheresis from severe (n = 7) and mild (n = 10) allergic patients and nonallergic subjects (n = 9) to perform platelet lipidomics by liquid chromatography coupled to mass spectrometry (LC-MS) and RNA-seq analysis. Significant metabolites and transcripts were used to identify compromised biological pathways in the severe phenotype. Platelet and inflammation-related proteins were quantified by Luminex.Results: Platelets from severe allergic patients were characterized by high levels of ceramides, phosphoinositols, phosphocholines, and sphingomyelins. In contrast, they showed a decrease in eicosanoid precursor levels. Biological pathway analysis performed with the significant lipids revealed the alteration of phospholipases, calcium-dependent events, and linolenic metabolism. RNAseq confirmed mRNA overexpression of genes related to platelet activation and arachidonic acid metabolism in the severe phenotypes. Pathway analysis indicated the alteration of NOD, MAPK, TLR, TNF, and IL-17 pathways in the severe phenotype. P-Selectin and IL-17AF proteins were increased in the severe phenotype.

Ageing-related delays and dysregulated inflammation in wound healing are well-documented in both human and animal models. However, cellular and molecular changes underlying this impairment in healing progression are not fully understood. In this study, we characterised ageing-associated changes to macrophages in wounds of young and aged mice and investigated transcriptomic differences that may impact the progression of wound healing. Full-thickness wounds created on the dorsum of C57BL/6J young and aged mice were excised on Days 3 and 7 post-wounding for analysis by immunohistochemistry, flow cytometry, and RNA sequencing. Our data revealed that macrophages were significantly reduced in aged wounds in comparison to young. Functional transcriptomic analyses showed that macrophages from aged wounds exhibited significantly reduced expression of cell cycle, DNA replication, and repair pathway genes. Furthermore, we uncovered an elevated pro-inflammatory gene expression program in the aged macrophages correlated with poor inflammation resolution and excessive tissue damage observed in aged wounds. Altogether, our work provides insights into how poorly healing aged wounds are phenotypically defined by the presence of macrophages with reduced proliferative capacity and an exacerbated inflammatory response, both of which are pathways that can be targeted to improve healing in the elderly.

The mammalian epidermis undergoes constant renewal replenished by a pool of stem cells and terminal differentiation of their progeny. This is accompanied by changes in gene expression and morphology orchestrated, in part, by epigenetic modifiers. Here, we defined the role of histone acetyltransferase KAT2A in epidermal homeostasis and provided a comparative analysis that revealed key functional divergence with its paralogue, KAT2B. In contrast to KAT2B's reported function in epidermal differentiation, KAT2A supports the undifferentiated state in keratinocytes. RNA-seq analysis of KAT2A- and KAT2B- depleted keratinocytes revealed dysregulated epidermal differentiation. Depletion of KAT2A led to premature expression of epidermal differentiation genes in the absence of inductive signals, whilst loss of KAT2B delayed differentiation. KAT2A acetyltransferase activity was indispensable in regulating epidermal differentiation gene expression. The metazoan-specific N-terminus of KAT2A was also required to support its function in keratinocytes. We further showed that the interplay between KAT2A- and KAT2B- mediated regulation was important for normal cutaneous wound healing in vivo. Overall, these findings reveal a distinct mechanism in which keratinocytes utilize a pair of highly homologous histone acetyltransferases to support divergent functions in self-renewal and differentiation processes.

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