Impaired wound healing associated with recurrent Staphylococcus aureus infection and unresolved inflammation are hallmarks of nonhealing diabetic foot ulcers (DFUs). Perforin-2, an innate immunity molecule against intracellular bacteria, limits cutaneous infection and dissemination of S. aureus in mice. Here, we report the intracellular accumulation of S. aureus in the epidermis of DFUs with no clinical signs of infection due to marked suppression of perforin-2. S. aureus residing within the epidermis of DFUs triggers AIM2 inflammasome activation and pyroptosis. These findings were corroborated in mice lacking perforin-2. The effects of pyroptosis on DFU clinical outcomes were further elucidated in a 4-week longitudinal clinical study in patients with DFUs receiving standard care. Increased AIM2 inflammasome and ASC-pyroptosome coupled with induction of IL-1β were found in nonhealing DFUs compared with healing DFUs. Our findings revealed that perforin-2 suppression, intracellular S. aureus accumulation, and associated induction of pyroptosis contribute to healing inhibition and prolonged inflammation in patients with DFUs.

Diabetic foot ulcers (DFUs) are a life-threatening disease that often results in lower limb amputations and a shortened life span. Current treatment options are limited and often not efficacious, raising the need for new therapies. To investigate the therapeutic potential of topical statins to restore healing in patients with DFUs, we performed next-generation sequencing on mevastatin-treated primary human keratinocytes. We found that mevastatin activated and modulated the EGF signaling to trigger an antiproliferative and promigratory phenotype, suggesting that statins may shift DFUs from a hyperproliferative phenotype to a promigratory phenotype in order to stimulate healing. Furthermore, mevastatin induced a migratory phenotype in primary human keratinocytes through EGF-mediated activation of Rac1, resulting in actin cytoskeletal reorganization and lamellipodia formation. Interestingly, the EGF receptor is downregulated in tissue biopsies from patients with DFUs. Mevastatin restored EGF signaling in DFUs through disruption of caveolae to promote keratinocyte migration, which was confirmed by caveolin-1 (Cav1) overexpression studies. We conclude that topical statins may have considerable therapeutic potential as a treatment option for patients with DFUs and offer an effective treatment for chronic wounds that can be rapidly translated to clinical use.

Calreticulin is recognized as a multifunctional protein that serves an essential role in diverse biological processes that include wound healing, modification and folding of proteins, regulation of the secretory pathway, cell motility, cellular metabolism, protein synthesis, regulation of gene expression, cell cycle regulation and apoptosis. Although the role of calreticulin as an endoplasmic reticulum-chaperone protein has been well described, several studies have demonstrated calreticulin to be a highly versatile protein with an essential role during wound healing. These features make it an ideal molecule for treating a complex, multifactorial diseases that require fine tuning, such as chronic wounds. Indeed, topical application of recombinant calreticulin to wounds in multiple models of wound healing has demonstrated remarkable pro-healing effects. Among them include enhanced keratinocyte and fibroblast migration and proliferation, induction of extracellular matrix proteins, recruitment of macrophages along with increased granulation tissue formation, all of which are important functions in promoting wound healing that are deregulated in chronic wounds. Given the high degree of diverse functions and pro-healing effects, application of exogenous calreticulin warrants further investigation as a potential novel therapeutic option for chronic wound patients. Here, we review and highlight the significant effects of topical application of calreticulin on enhancing wound healing and its potential as a novel therapeutic option to shift chronic wounds into healing, acute-like wounds.

Hidradenitis Suppurativa (HS) is a chronic multifactorial inflammatory skin disease with a debilitating impact on quality of life. Here, we review the complex interplay of innate and adaptive immune dysregulation in HS pathogenesis, in the context of microbial dysbiosis, genetic predisposition, cellular dysfunction and epigenetic factors. Hyperactivation of the innate system triggered by follicular occlusion leads to a cascade of activated signaling pathways leading to persistent inflammation as the disease progresses. This immune hyperactivation is further complicated by microbiome dysbiosis, which is associated with dysregulation of inflammasomes and altered expression of host antimicrobial peptides. Keratinocytes, fibroblasts, macrophages, and neutrophils exhibit altered functions, and contribute to the inflammatory cascade and disease chronicity in HS. Epigenetic mechanisms including DNA methylation, histone modifications, and non-coding RNAs modulate immune responses and contribute to aberrant cytokine and chemokine expression that drive the persistent inflammatory state in HS pathogenesis. We highlight the need for future research to explore the concept of epigenetic memory in epidermal stem cells and inflammasome activation to gain a better understanding of these mechanisms and pave the way for development of future novel therapeutic targets and strategies to disrupt the persistent chronic inflammation cycle in this debilitating condition.

Traumatic brain injury (TBI) is a significant public health concern, often resulting in long-term impairments. TBI is also a known risk factor for Alzheimer’s disease (AD), with both conditions sharing features such as inflammasome dysregulation. Inflammasome proteins are carried in extracellular vesicles (EVs) derived from blood plasma and serum. Our previous work showed that TBI in the context of AD acutely increases inflammasome activation and accelerates pathology. However, chronic effects of TBI in AD, particularly regarding sex differences, remain poorly characterized. Here, we used 3xTg-AD mice and wild-type (WT) controls, which underwent moderate controlled cortical impact (CCI) or sham surgery at 5 months of age. Mice were sacrificed at 3 months post-injury for biochemical and histopathological analysis. Cortical and hippocampal lysates were analyzed for inflammasome proteins and inflammatory cytokines via immunoblotting, while pathological markers were assessed using Ella Simple Plex technology and histopathology. In a separate cohort, 3xTg mice received moderate CCI and were sacrificed 7 days post-injury to evaluate sex differences. Cortical lysates were tested for pro-inflammatory cytokines and pathological markers via electrochemiluminescent immunoassay, and EVs were analyzed using mass spectrometry. AD-TBI mice showed increased expression of inflammasome proteins, pro-inflammatory cytokines, and glial fibrillary acidic protein (GFAP). TBI mice displayed elevated neurofilament light in the cortex, with both GFAP and neurofilament light co-localizing with inflammasome proteins in the perilesional cortex. Moreover, AD-TBI mice exhibited reduced cortical and hippocampal volumes compared to WT-TBI mice. In the sex differences cohort, EVs from male and female AD-TBI mice showed distinct patterns in upstream regulators and signaling pathways. Female-derived EVs showed greater activation of AD-related pathways. Sex-specific differences were also observed in cortical pro-inflammatory cytokine expression, although GFAP and amyloid-β levels were not significantly different between sexes. This study demonstrates that AD leads to changes in chronic inflammasome expression and neurodegenerative pathology, with marked sex-dependent differences in inflammatory and signaling responses in AD with TBI. These findings underscore the importance of considering both AD comorbidity and biological sex in the evaluation of TBI outcomes and therapeutic strategies.