Modulation of TRPM8 alters the phagocytic activity of microglia and induces changes in sub-cellular organelle functions

TRPM8 activation inhibits neuroinflammation and ameliorates neurodegeneration by modulating Nrf2/HO-1 and NF-κB pathways in vivo and in vitro

Neuroinflammation plays a pivotal role in the progression of Parkinson's disease (PD), and molecules capable of inhibiting neuroinflammation hold significant promise as therapeutic targets for PD. The transient receptor potential melastatin 8 (TRPM8), a transmembrane protein with well-documented anti-inflammatory properties, is prominently expressed in macrophages. This study marks the first exploration of the anti-PD effects of TRPM8 activation and its underlying mechanisms. Experimental results demonstrate that Icilin, a small-molecule TRPM8 agonist, conferred beneficial effects in a PD mouse model, including improved motor function, reduced dopaminergic neuronal damage, and suppressed neuroinflammation. Mechanistically, Icilin alleviated neuroinflammation in microglia through TRPM8 activation, which modulated the Nrf2/HO-1 and NF-κB pathways, thereby shielding neurons from microglia-mediated inflammatory injury. These findings not only underscore the therapeutic potential of TRPM8 in PD but also highlight its relevance to functional food science, as TRPM8 activation could be harnessed to develop dietary interventions with neuroprotective and anti-inflammatory properties. In conclusion, our study identifies TRPM8 as a promising therapeutic target for PD by regulating neuroinflammation via the Nrf2/HO-1 and NF-κB pathways, offering novel insights for the development of functional foods aimed at mitigating neurodegenerative diseases.

The Complementary Role of Morphology in Understanding Microglial Functional Heterogeneity

A search of the PubMed database for publications on microglia reveals an intriguing shift in scientific interest over time. Dividing microglia into categories such as "resting" and "activated" or M1 versus M2 is nowadays obsolete, with the current research focusing on unraveling microglial heterogeneity. The onset of transcriptomics, especially single-cell RNA sequencing (scRNA-seq), has profoundly reshaped our understanding of microglia heterogeneity. Conversely, microglia morphology analysis can offer important insights regarding their activation state or involvement in tissue responses. This review explores microglial heterogeneity under homeostatic conditions, developmental stages, and disease states, with a focus on integrating transcriptomic data with morphological analysis. Beyond the core gene expression profile, regional differences are observed with cerebellar microglia exhibiting a uniquely immune-vigilant profile. During development, microglia express homeostatic genes before birth, yet the bushy appearance is a characteristic that appears later on. In neurodegeneration, microglia alternate between proinflammatory and neuroprotective roles, influenced by regional factors and disease onset. Understanding these structural adaptations may help identify specific microglial subpopulations for targeted therapeutic strategies.

A predictive machine learning model for cannabinoid effect based on image detection of reactive oxygen species in microglia

Neuroinflammation is a key feature of human neurodisease including neuropathy and neurodegenerative disease and is driven by the activation microglia, immune cells of the nervous system. During activation microglia release pro-inflammatory cytokines as well as reactive oxygen species (ROS) that can drive local neuronal and glial damage. Phytocannabinoids are an important class of naturally occurring compounds found in the cannabis plant (Cannabis sativa) that interact with the body's endocannabinoid receptor system. Cannabidiol (CBD) is a prototype phytocannabinoid with anti-inflammatory properties observed in cells and animal models. We measured ROS in human microglia (HMC3) cells using CellROX, a fluorescent dynamic ROS indicator. We tested the effect of CBD on ROS level in the presence of three known immune activators: lipopolysaccharide (LPS), amyloid beta (Aβ42), and human immunodeficiency virus (HIV) glycoprotein (GP120). Confocal microscopy images within microglia were coupled to a deep learning model using a convolutional neural network (CNN) to predict ROS responses. Our study demonstrates a deep learning platform that can be used in the assessment of CBD effect in immune cells using ROS image measure.

TRPM8 affects relative "cooling and heating" of subcellular organelles in microglia in a context-dependent manner

Thermoregulation and thermal homeostasis at the cellular and subcellular organelle level are poorly understood events. In this work, we used BV2, a microglial cell line, and a series of thermo-sensitive subcellular organelle-specific probes to analyze the relative changes in the spatio-temporal temperatures of different subcellular organelles, both qualitatively and quantitatively. These methodologies allowed us to understand the thermal relationship of different subcellular organelles also. We modulated BV2 cells by pharmacological application of activator or inhibitor of TRPM8 ion channel (a cold-sensitive ion channel) and/or by treating the cells with LPS, a molecule that induces pathogen-associated molecular patterns (PAMPs) signaling. We demonstrate that the temperatures of individual organelles remain variable within a physiological range, yet vary in different conditions. We also demonstrate that treating BV2 cells by TRPM8 modulators and/or LPS alters the organelle temperatures in a specific and context-dependent manner. We show that TRPM8 modulation and/or LPS can alter the relationship of mitochondrial membrane potential to mitochondrial temperature. Our work suggests that mitochondrial temperature positively influences ER temperature and negatively influences Golgi temperature. Golgi temperature positively influences membrane temperature. This understanding of thermal relationships may be crucial for dissecting cellular structures, function, and stress signaling and may be relevant for different diseases.

The role of transient receptor potential (TRP) channels in phagocytosis: A comprehensive review

When host cells are exposed to foreign particles, dead cells, or cell hazards, a sophisticated process called phagocytosis begins. During this process, macrophages, dendritic cells, and neutrophils engulf the target by expanding their membranes. Phagocytosis of apoptotic cells is called efferocytosis. This process is of significant importance as billions of cells are eliminated daily without provoking inflammation. Both phagocytosis and efferocytosis depend on Ca2+ signaling. A big family of Ca2+ permeable channels is transient receptor potentials (TRPs) divided into nine subfamilies. We aimed to review their roles in phagocytosis. The present review article shows that various TRP channels such as TRPV1, 2, 3, 4, TRPM2, 4, 7, 8, TRPML1, TRPA1, TRPC1, 3, 5, 6 have roles at various stages of phagocytosis. They are involved in the phagocytosis of amyloid β, α-synuclein, myelin debris, bacteria, and apoptotic cells. In particular, TRPC3 and TRPM7 contribute to efferocytosis. These effects are mediated by changing Ca2+ signaling or targeting intracellular enzymes such as Akt. In addition, they contribute to the chemotaxis of phagocytic cells towards targets. Although a limited number of studies have assessed the role of TRP channels in phagocytosis and efferocytosis, their findings indicate that they have critical roles in these processes. In some cases, their ablation completely abolished the phagocytic function of the cells. As a result, TRP channels are potential targets for developing new therapeutics that modulate phagocytosis.