LETHAL COVID-19 ASSOCIATES WITH RAAS-INDUCED INFLAMMATION FOR MULTIPLE ORGAN DAMAGE INCLUDING MEDIASTINAL LYMPH NODES (preprint)

Lethal COVID-19 causation most often invokes classic cytokine storm and attendant excessive immune signaling. We re-visit this question using RNA sequencing in nasopharyngeal and 40 autopsy samples from both COVID-19-positive and negative individuals. In nasal swabs, the top 100 genes expressed, and significantly correlated with COVID-19 viral load, indeed include many canonical innate immune genes. However, 22 much less studied \"non-canonical\" genes are found and despite the absence of viral transcripts, subsets of these are upregulated in heart, lung, kidney, and liver, but not mediastinal lymph nodes. An important regulatory potential emerges for the non-canonical genes for over-activating the renin-angiotensin-activation-system (RAAS) pathway, resembling this phenomenon in hereditary angioedema (HAE) and its overlapping multiple features with lethal COVID-19 infections. Specifically, RAAS overactivation links increased fibrin deposition, leaky vessels, thrombotic tendency, and initiating the PANoptosis death pathway, as suggested in heart, lung, and especially mediastinal lymph nodes, and a tight association mitochondrial dysfunction linked to immune responses. For mediastinal lymph nodes, immunohistochemistry studies correlate showing abnormal architecture, excess fibrin and collagen deposition, and pathogenic fibroblasts. Further, our findings overlap these for COVID-19 infected hamsters, C57BL/6 and BALB/c mouse models, and importantly peripheral blood mononuclear cell (PBMC) and whole blood samples from COVID-19 patients infected with early alpha but also later COVID-19 omicron strains. We thus present cytokine storm in lethal COVID-19 disease as an interplay between upstream immune gene signaling producing downstream RAAS overactivation with resultant severe organ damage, especially compromising mediastinal lymph node function.

Functional Multi-Omics Reveals Noncanonical Function of G9a in Translational Regulation of Chronic Inflammation (preprint)

By largely unknown mechanisms, dysregulated gene-specific translation directly contributes to chronic inflammation-associated diseases such as sepsis and ARDS. Here, we report that G9a, a histone methyltransferase and well-regarded transcriptional repressor, non-canonically or non-epigenetically activates translation of select antimicrobial genes to promote proliferation of cytokine producing macrophages and to impair T cell function; all hallmarks of endotoxin-tolerance related complications including sepsis, ARDS and COVID19. Mechanistically, G9a interacts with translation regulators including METTL3, an N6-methyladenosine or m6A RNA methyltransferase, and methylates it to cooperatively upregulate the translation of certain m6A-modified mRNAs that encode immune checkpoint and anti-inflammatory proteins. Further, translatome proteomic analysis of ET macrophages progressively treated by a G9a inhibitor identified proteins showing G9a-dependent translation that unite the networks associated with hyperinflammation and T cell dysfunction. Overall, we identified a previously unrecognized function of G9a in gene-specific translation that can be leveraged to treat ET-related chronic inflammatory diseases.