Myeloid-derived suppressor cells exacerbate poly(I:C)-induced lung inflammation in mice with renal injury and older mice

Protective Effects of NRF2 Activator Sulforaphane in Polyinosinic:Polycytidylic Acid-Induced In Vitro and In Vivo Model

NRF2 is a nuclear transcription factor involved in the cellular protection against oxidative stress and inflammatory signaling. Sulforaphane is a known NRF2 activator used for its strong antioxidant and anti-inflammatory activity through regulation of Keap-1-HO-1 pathway. However, there is a limited exploration about the role of NRF2 activator, sulforaphane in regulation of poly(I:C)-induced oxidative stress, inflammation and injury in lung. Therefore, we aimed to evaluate the therapeutic effect of sulforaphane in poly(I:C)-induced responses using in vitro as well as in vivo model. We evaluated oxidative stress and inflammatory cytokines in poly(I:C)-induced RAW264.7 cells. We also employed in vivo animal study to evaluate tissue oxidative-antioxidative balance along with expression of NRF2, Keap-1, histopathological assessment by hematoxylin-eosin staining and picrosirius red staining to explore the protective mechanisms of sulforaphane in poly(I:C)-induced mouse model. Our results indicated that sulforaphane increased the expression of NRF2 and its downstream proteins. In addition, sulforaphane alleviated poly(I:C)-induced activation of the oxidative and pro-inflammatory pathways, histopathological changes, depleted expression of GSH and superoxide dismutase in lung tissue. This study suggested that sulforaphane may be one of the useful therapeutic alternatives for poly(I:C) induced lung injury and inflammation.

ACE2 improves endothelial cell function and reduces acute lung injury by downregulating FAK expression

Endothelial cell (EC) barrier dysfunction and increased adhesion of immune inflammatory cells to ECs crucially contribute to acute lung injury (ALI). Angiotensin-converting enzyme 2 (ACE2) is an essential regulator of the renin-angiotensin system (RAS) and exerts characteristic vasodilatory and anti-inflammatory effects. SARS-COV-2 infects the lungs by binding to ACE2, which can lead to dysregulation of ACE2 expression, further leading to ALI with predominantly vascular inflammation and eventually to more severe acute respiratory distress syndrome (ARDS). Therefore, restoration of ACE2 expression represents a valuable therapeutic approach for SARS-COV-2-related ALI/ARDS. In this study, we used polyinosinic-polycytidylic acid (Poly(I:C)), a double-stranded RNA analog, to construct a mouse ALI model that mimics virus infection. After Poly(I:C) exposure, ACE2 was downregulated in mouse lung tissues and in cultured ECs. Treatment with DIZE, an ACE2-activating compound, upregulated ACE2 expression and relieved ALI in mice. DIZE also improved barrier function and reduced the number of THP-1 monocytes adhering to cultured ECs. Focal adhesion kinase (FAK) and phosphorylated FAK (p-FAK) levels were increased in lung tissues of ALI mice as well as in Poly(I:C)-treated ECs in vitro. Both DIZE and the FAK inhibitor PF562271 decreased FAK/p-FAK expression in both ALI models, attenuating ALI severity in vivo and increasing barrier function and reducing monocyte adhesion in cultured ECs. Furthermore, in vivo experiments using ANG 1-7 and the MAS inhibitor A779 corroborated that DIZE-mediated ACE2 activation stimulated the activity of the ANG 1-7/MAS axis, which inhibited FAK/p-FAK expression in the mouse lung. These findings provide further evidence that activation of ACE2 in ECs may be a valuable therapeutic strategy for ALI.