Extrafollicular IgD-CD27-CXCR5-CD11c- DN3 B cells infiltrate inflamed tissues in autoimmune fibrosis and in severe COVID-19

Although therapeutic B cell depletion dramatically resolves inflammation in many diseases in which antibodies appear not to play a central role, distinct extrafollicular pathogenic B cell subsets that accumulate in disease lesions have hitherto not been identified. The circulating immunoglobulin D (IgD)-CD27-CXCR5-CD11c+ DN2 B cell subset has been previously studied in some autoimmune diseases. A distinct IgD-CD27-CXCR5-CD11c- DN3 B cell subset accumulates in the blood both in IgG4-related disease, an autoimmune disease in which inflammation and fibrosis can be reversed by B cell depletion, and in severe COVID-19. These DN3 B cells prominently accumulate in the end organs of IgG4-related disease and in lung lesions in COVID-19, and double-negative B cells prominently cluster with CD4+ T cells in these lesions. Extrafollicular DN3 B cells may participate in tissue inflammation and fibrosis in autoimmune fibrotic diseases, as well as in COVID-19.

Cardioprotective and anti-inflammatory effects of Caveolin 1 in experimental diabetic cardiomyopathy

Previous studies of the Caveolin 1 (Cav1) protein and caveolae, which are lipid raft structures found on the plasma membranes of certain cells, are associated with fat metabolism disorders, inflammation, diabetes, and cardiovascular disease. However, there have been no reports linking Cav1 to diabetic cardiomyopathy (DCM). In the present study, we established a relationship between Cav1 and the development of DCM. We found that compared with Cav1+/+ mice, Cav1-/- diabetic mice exhibited more severe cardiac injury, increased activation of NF-κB signaling, and up-regulation of downstream genes, including hypertrophic factors and inflammatory fibrosis factors in heart tissues. Additionally, in vitro results showed that knocking down Cav1 further activated HG-induced NF-κB signaling, increased the expression of downstream target genes, and decreased the expression of inhibitor α of NF-κB (iκBα), all of which have been linked to DCM pathogenesis. In contrast, Cav1 overexpression resulted in the opposite effects. Our study suggests that Cav1 knockdown promotes cardiac injury in DCM by activating the NF-κB signaling pathway, and targeting Cav1 may lead to the development of novel treatments for DCM.

Progestin and AdipoQ Receptor 3 Upregulates Fibronectin and Intercellular Adhesion Molecule-1 in Glomerular Mesangial Cells via Activating NF-κB Signaling Pathway Under High Glucose Conditions

BACKGROUND

Progestin and adipoQ receptor 3 (PAQR3), is a Golgi-anchored membrane protein containing seven transmembrane helices. It has been demonstrated that PAQR3 mediates insulin resistance, glucose and lipid metabolism, and inflammation. In addition, kidney inflammatory fibrosis is an important pathological feature of diabetic nephropathy (DN). Therefore, we aimed to investigate the role of PAQR3 in diabetic kidney fibrosis as well as inflammation in DN.

OBJECT

The effect of PAQR3 on NF-κB signaling pathway, expressions of fibronectin (FN) and intercellular adhesion molecule-1 (ICAM-1) in glomerular mesangial cells (GMCs) cultured by high glucose (HG) were examined.

METHOD

Diabetic mouse and rat models were induced by streptozotocin (STZ). GMCs were treated with HG and transfected with PAQR3 plasmids or small-interfering RNA targeting PAQR3 or NF-κB. The protein levels of FN and ICAM-1 were examined by Western blotting, and the transcriptional activity and DNA binding activity of NF-κB were measured by dual luciferase reporter assay and electrophoretic mobility shift assay (EMSA). The interaction between PAQR3 and IKKβ (inhibitor of nuclear factor κB kinase β) was analyzed by co-immunoprecipitation.

RESULTS

PAQR3 was increased in both STZ-induced diabetic models and HG-treated GMCs. PAQR3 overexpression further increased HG-induced FN and ICAM-1 upregulation. In contrast, silencing of PAQR3 suppressed the expressions of FN and ICAM-1. PAQR3 overexpression promoted the nuclear accumulation, DNA binding activity, and transcriptional activity of NF-κB. Mechanically, PAQR3 directly interacted with IKKβ. The upregulation effect of PAQR3 overexpression on the expressions of FN and ICAM-1 was abolished by the treatment of NF-κB siRNA or PDTC (ammonium pyrrolidinedithiocarbamate) in HG-treated GMCs.

CONCLUSION

PAQR3 promotes the expressions of FN and ICAM-1 via activating NF-κB signaling pathway. Mechanistically, PAQR3 activates NF-κB signaling pathway to mediate kidney inflammatory fibrosis through direct interaction with IKKβ in DN.

Mast Cells Play an Important Role in the Pathogenesis of Hyperglycemia-Induced Atrial Fibrillation

BACKGROUND AND OBJECTIVES

Recently, it was reported that mast cells (MCs) could underlie the mechanisms of several cardiovascular diseases. However, the role of MCs in diabetes-induced atrial fibrillation (AF) has not been notably investigated. We tested the hypothesis that MC deficiency attenuates hyperglycemia-induced AF in mice.

METHODS AND RESULTS

Mast cell-deficient W/W(v)  mice, and congenic +/+ littermates (WT) were divided into either the vehicle (VEH)-injection group or the streptozotocin (STZ)-injection group (MCKO-VEH, MCKO-STZ, WT-VEH, and WT-STZ groups). On day 28 of our studies, we observed that (1) STZ-induced hyperglycemia increased MC infiltration in the left atrium (LA) in WT mice (P < 0.01), (2) atrium isolated from the WT-STZ group showed inhomogeneous interstitial fibrosis, abundant infiltration of macrophages, and enhanced apoptosis compared to the WT-VEH group (P < 0.01, P < 0.01, P < 0.05, respectively). However, the changes observed in the WT-STZ group were significantly attenuated in the MCKO-STZ mice. In addition, we observed that (3) messenger RNA levels of tumor necrosis factor-α, monocyte chemoattractant protein-1, interleukin-1β, transforming growth factor-β, and collagen-1 in the LA were increased in the WT-STZ group, but not in the MCKO-STZ group, (4) STZ-induced hyperglycemia increased AF induction and prolonged interatrial conduction time in the WT mice, which were not observed in the MCKO mice, and that (5) hyperglycemia-enhanced atrial production of reactive oxygen species (ROS) was equally observed in the WT and MCKO mice.

CONCLUSIONS

Our results suggest that MCs contribute to the pathogenesis of hyperglycemia-induced AF via enhancement of inflammation and fibrosis.