Early suppression of antiviral host response and protocadherins by SARS-CoV-2 Spike protein in THP-1-derived macrophage-like cells

Toll-like Receptors 1, 3 and 7 Activate Distinct Genetic Features of NF-κB Signaling and γ-Protocadherin Expression in Human Cardiac Fibroblasts

Fibroblasts play a pivotal role in key processes within the heart, particularly in cardiac remodeling that follows both ischemic and non-ischemic injury. During remodeling, fibroblasts drive fibrosis and inflammation by reorganizing the extracellular matrix and modulating the immune response, including toll-like receptor (TLR) activation, to promote tissue stabilization. Building on findings from our prior research on heart tissue from patients with advanced coronary artery disease and aortic valve disease, this study sought to explore specific effects of TLR1, TLR3, and TLR7 activation on NF-κB signaling, proinflammatory cytokine production, and γ-protocadherin expression in cardiac fibroblasts. Human cardiac fibroblasts were exposed to agonists for TLR1, TLR3, or TLR7 for 24 h, followed by an analysis of NF-κB signaling, cytokine production, and γ-protocadherin expression. The activation of these TLRs triggered distinct responses in the NF-κB signaling pathway, with TLR3 showing a stronger activation profile compared to TLR1 and TLR7, particularly in downregulating γ-protocadherin expression. These findings highlight a potential role for TLR3 in amplifying inflammatory responses and reducing γ-protocadherin levels in cardiac fibroblasts, correlating with the enhanced inflammation and lower γ-protocadherin expression observed in diseased myocardium from patients with coronary artery disease and aortic valve disease. Consequently, TLR3 represents a potential therapeutic target for modulating immune responses in cardiovascular diseases.

Vitamin D regulates COVID-19 associated severity by suppressing the NLRP3 inflammasome pathway

BACKGROUND

The role of vitamin D3 (VitD3) in modulating innate and adaptive immunity has been reported in different disease contexts. Since the start of the coronavirus disease-2019 (COVID-19) pandemic, the role of VitD3 has been highlighted in many correlational and observational studies. However, the exact mechanisms of action are not well identified. One of the mechanisms via which VitD3 modulates innate immunity is by regulating the NLRP3-inflammasome pathway, being a main underlying cause of SARS-CoV-2-induced hyperinflammation.

AIMS AND MAIN METHODS

Blood specimens of severe COVID-19 patients with or without VitD3 treatment were collected during their stay in the intensive care unit and patients were followed up for 29 days. qPCR, western blot, and ELISA were done to investigate the mechanism of action of VitD3 on the NLRP3 inflammasome activation.

KEY FINDINGS

We here report the ability of VitD3 to downregulate the NLRP3-inflammsome pathway in severe COVID-19 patients. Lower inflammasome pathway activation was observed with significantly lower gene and protein expression of NLRP3, cleaved caspase-1, ASC and IL-1β among severe COVID-19 patients treated with VitD3. The reduction of the inflammasome pathway was associated with a reduction in disease severity markers and enhancement of type I IFN pathway.

SIGNIFICANCE

Our data reveals an important anti-inflammatory effect of VitD3 during SARS-CoV-2 infection. Further investigations are warranted to better characterize the ability of VitD3 to control disease pathogenesis and prevent progression to severe states. This will allow for a more efficient use of a low cost and accessible treatment like VitD3.