Mast Cells Mediate Rheumatoid Arthritis-Inhibitory Role of IL-37

Identification of shared disease marker genes and underlying mechanisms between major depression and rheumatoid arthritis

Both depression and rheumatoid arthritis (RA) have a very high comorbidity rate. A bilateral association is estimated to increase the mutual risk and the common denominator is inflammation being observed in both diseases. Previous studies have mainly focused on assessing peripheral blood's inflammatory and pro-inflammatory cytokines levels. We aimed to extend insights into the molecular mechanisms of depression based on hub RA genes. To do so, we prioritized RA-related genes using in-silico tools. We then investigated whether RA-related genes undergo altered expression in patients with unipolar and bipolar depression without a concurrent RA diagnosis and any exponents of active inflammation. In addition, we selected a homogeneous group of patients treated with lithium (Li), which has immunomodulatory properties. The study was performed on patients with bipolar depression (BD, n = 45; Li, n = 20), unipolar depression (UD, n = 27), and healthy controls (HC, n = 22) of both sexes. To identify DEGs in peripheral blood mononuclear cells (PBMCs), we used the SurePrint G3 Microarray and GeneSpring software. We selected a list of 180 hub genes whose altered expression we analyzed using the expression microarray results. In the entire study group, we identified altered expression of 93 of the 180 genes, including 35 down-regulated (OPRM1 gene with highest FC > 3) and 58 up-regulated (TLR4 gene with highest FC > 3). In UD patients, we observed maximally up-regulated expression of the TEK gene (FC > 3), and in BD of the CXCL8 gene (FC > 5). On the other hand, in lithium-treated patients, the gene with the most reduced expression was the TRPV1 gene. The study proved that depression and RA are produced by a partially shared "inflammatory interactome" in which the opioid and angiogenesis pathways are important.

Bidirectional communication between mast cells and the gut-brain axis in neurodegenerative diseases: Avenues for therapeutic intervention

Although the global incidence of neurodegenerative diseases has been steadily increasing, especially in adults, there are no effective therapeutic interventions. Neurodegeneration is a heterogeneous group of disorders that is characterized by the activation of immune cells in the central nervous system (CNS) (e.g., mast cells and microglia) and subsequent neuroinflammation. Mast cells are found in the brain and the gastrointestinal tract and play a role in "tuning" neuroimmune responses. The complex bidirectional communication between mast cells and gut microbiota coordinates various dynamic neuro-cellular responses, which propagates neuronal impulses from the gastrointestinal tract into the CNS. Numerous inflammatory mediators from degranulated mast cells alter intestinal gut permeability and disrupt blood-brain barrier, which results in the promotion of neuroinflammatory processes leading to neurological disorders, thereby offsetting the balance in immune-surveillance. Emerging evidence supports the hypothesis that gut-microbiota exert a pivotal role in inflammatory signaling through the activation of immune and inflammatory cells. Communication between inflammatory cytokines and neurocircuits via the gut-brain axis (GBA) affects behavioral responses, activates mast cells and microglia that causes neuroinflammation, which is associated with neurological diseases. In this comprehensive review, we focus on what is currently known about mast cells and the gut-brain axis relationship, and how this relationship is connected to neurodegenerative diseases. We hope that further elucidating the bidirectional communication between mast cells and the GBA will not only stimulate future research on neurodegenerative diseases but will also identify new opportunities for therapeutic interventions.