Biology subjects

Pacifico, P.

Publications and source records attributed to Pacifico, P..

4 recordsLinked to original sources

bioRxiv2026

Targeting GPR183 to reduce peripheral sensitization: evidence from rodent and human tissue analyses

Peripheral sensitization is a key process in the development of painful inflammatory conditions, driven in part by immune-cell mediator release following tissue injury. The G protein-coupled receptor, GPR183, predominantly expressed on immune cells, regulates their migration, positioning, and mediator production. Yet its role in peripheral sensitization and the specific immune cells involved remains insufficiently understood. In rats, intraplantar injection of 7,25-dihydroxycholesterol (7,25-OHC), the most potent endogenous GPR183 ligand, produced long-lasting nociception that was prevented by the selective GPR183 antagonist SAE-14. Because GPR183 activates ERK signaling, which influences pain pathways including nitric oxide synthase (NOS) activity and NO formation, we used NOS inhibitors and knockout animals to test the contribution of inducible and neuronal NOS isoforms to 7,25-OHC-induced sensitization. We found that both isoforms influence this response, independent of cyclooxygenases. In a well-characterized rat incisional injury model, GPR183 protein expression increased in injured paw tissue, and SAE-14 reversed hypersensitivity. Meta-analysis of human post-surgical skin samples similarly showed elevated GPR183 expression and transcriptional changes favoring 7,25-OHC production after injury. We identified macrophages and Langerhans cells (LCs) as the principal GPR183-expressing cell types in human skin. LC ablation studies revealed that 7,25-OHC-evoked hypersensitivity does not depend on LCs, implicating GPR183+ macrophages as predominant drivers of GPR3-induced hypersensitivity. Overall, our findings define the cellular and molecular pathways linking GPR183 to peripheral sensitization and highlight GPR183 antagonism as a promising strategy for pain management.

pharmacology and toxicology↗

bioRxiv2025

Epidermal Langerhans Cells Drive Painful Diabetic Neuropathy in a Sex-dependent Manner

The interaction between non-neuronal cells and nerve endings in the epidermis significantly influences the development of various diseases, including Painful Diabetic Neuropathy (PDN). PDN is a common and challenging complication of diabetes, characterized by changes in skin innervation accompanied by neuropathic pain. While there is growing evidence that epidermal non-neuronal cells, such as resident immune cells, play a crucial role in the progression of PDN, the underlying mechanisms of this neuropathy remain poorly understood. In our studies, we utilized transgenic methods, pain behavioral assessments, and single-cell RNA sequencing (scRNAseq) in a clinically relevant high-fat diet (HFD) mouse model of PDN and skin biopsy samples from PDN patients, to investigate the role of epidermal Langerhans cells (LCs) in this condition. We observed an increased density of LCs in the skin of PDN male mice coinciding with the onset of mechanical allodynia. Furthermore, we found that LCs density correlated with small fiber degeneration in HFD mice and skin biopsies taken from well-characterized PDN patients compared to healthy controls. Importantly, the selective ablation of LCs using a diphtheria-toxin strategy was found to prevent nociceptive behavior in male mice. This indicates that LCs are both necessary and sufficient for the development of mechanical allodynia and spontaneous pain in HFD male mice. Interestingly, when LCs were ablated in HFD female mice, it did not prevent but rather promoted pain behavior, suggesting the existence of sex-specific mechanisms mediated by LCs. scRNAseq transcriptomic analysis of the paw epidermis from HFD mice, which included both males and females, revealed significant sex-mediated differences in the expression of specific target genes within this PDN model. In male mice, scRNAseq identified differentially expressed genes associated with axonal guidance and immune responses in LCs. Additionally, by integrating single-cell RNA data from the epidermis and dorsal root ganglia (DRG) of male mice, we uncovered altered communication between LCs and cutaneous afferents through Semaphorin-Plexin signaling pathways in PDN. These findings highlight LCs as key contributors to the development of PDN and suggest their potential as therapeutic targets for innovative treatments, particularly topical therapies aimed at modulating immune cell activity and neuroimmune communication in the skin. Our investigations of male and female mice indicate that LCs may play different roles in mechanical sensation under both normal and pathological conditions, such as PDN. This underscores the importance of considering sex differences when developing more effective treatments. BRIEF SUMMARYThe interaction between non-neuronal cells and nerve endings in the epidermis plays a significant role in the development of Painful Diabetic Neuropathy (PDN), a challenging complication of diabetes. Using transgenic methods, pain behavioral assessments, and single-cell transcriptomics in a clinically relevant high-fat diet (HFD) mouse model of PDN, and in skin tissues from PDN patients, we identified epidermal Langerhans cells (LCs) as key contributors to the development of PDN. In these studies, we revealed, for the first time, a dimorphic role for LCs in the development of mechanical allodynia and spontaneous pain in a HFD model of PDN. Single-cell RNA sequencing (scRNAseq) of the paw epidermis from both male and female HFD mice identified sex-mediated differences in the expression of specific target genes within this PDN model. In male mice, scRNAseq of LCs revealed differentially expressed genes related to immune responses and axonal guidance, including Semaphorin-Plexin signaling pathways.

neuroscience↗

bioRxiv2024

Keratinocyte-derived exosomes in painful diabetic neuropathy

Painful diabetic neuropathy (PDN) is a challenging complication of diabetes with patients experiencing a painful and burning sensation in their extremities. Existing treatments provide limited relief without addressing the underlying mechanisms of the disease. PDN involves the gradual degeneration of nerve fibers in the skin. Keratinocytes, the most abundant epidermal cell type, are closely positioned to cutaneous nerve terminals, suggesting the possibility of bi-directional communication. Exosomes are small extracellular vesicles released from many cell types that mediate cell to cell communication. The role of keratinocyte-derived exosomes (KDEs) in influencing signaling between the skin and cutaneous nerve terminals and their contribution to the genesis of PDN has not been explored. In this study, we characterized KDEs in a well-established high-fat diet (HFD) mouse model of PDN using primary adult mouse keratinocyte cultures. We obtained highly enriched KDEs through size exclusion chromatography and then analyzed their molecular cargo using proteomic analysis and small RNA sequencing. We found significant differences in the protein and microRNA content of HFD KDEs compared to KDEs obtained from control mice on a regular diet (RD), including pathways involved in axon guidance and synaptic transmission. Additionally, using an in vivo conditional extracellular vesicle (EV) reporter mouse model, we demonstrated that epidermal-originating GFP-tagged KDEs are retrogradely trafficked into the DRG neuron cell body. Overall, our study presents a potential novel mode of communication between keratinocytes and DRG neurons in the skin, revealing a possible role for KDEs in contributing to the axonal degeneration that underlies neuropathic pain in PDN. Moreover, this study presents potential therapeutic targets in the skin for developing more effective, disease-modifying, and better-tolerated topical interventions for patients suffering from PDN, one of the most common and untreatable peripheral neuropathies.

neuroscience↗

bioRxiv2017

Control of mechanical pain hypersensitivity through ligand-targeted photoablation of TrkB positive sensory neurons

SummaryMechanical allodynia is a major symptom of neuropathic pain whereby innocuous touch evokes severe pain. Here we identify a population of peripheral sensory neurons expressing TrkB that are both necessary and sufficient for producing pain from light touch after nerve injury. Mice in which TrkB-Cre expressing neurons are ablated are less sensitive to the lightest touch under basal conditions, and fail to develop mechanical allodynia in a model of neuropathic pain. Moreover, selective optogenetic activation of these neurons after nerve injury evokes marked nociceptive behavior. Using a phototherapeutic approach based upon BDNF, the ligand for TrkB, we perform molecule-guided laser ablation of these neurons and achieve long-term retraction of TrkB positive neurons from the skin and pronounced reversal of mechanical allodynia across multiple types of neuropathic pain. Thus we identify the peripheral neurons which transmit pain from light touch and uncover a novel pharmacological strategy for its treatment.\n\nHighlightsO_LITrkB+ neurons detect light touch under basal conditions\nC_LIO_LITrkB+ neurons convey mechanical allodynia in neuropathic pain states\nC_LIO_LIA photosensitizing derivative of BDNF allows for photoablation of TrkB+ neurons\nC_LIO_LIBDNF-guided photoablation reverses allodynia in multiple types of neuropathic pain\nC_LI

neuroscience↗