Increased Inflammasome Activation Is Associated with Aging and Chronic Myelomonocytic Leukemia Disease Severity

Aging causes chronic low-grade inflammation known as inflamm-aging. It is a risk factor for several chronic disorders, including chronic myelomonocytic leukemia (CMML), a hematological malignancy that is most prevalent in older people. Recent studies suggest a critical role for the NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome in inflamm-aging. However, the mechanisms involved in NLRP3 activation in aging and its involvement in CMML progression are not fully understood. In this study, we report that aging increases IL-1β production upon NLRP3 activation in human CD14+ monocytes. Interestingly, we found that the TLR1/2 agonist Pam3CSK4 directly activates the NLRP3 inflammasome in monocytes from older but not from younger healthy donors. Furthermore, we observed a dichotomous response to NLRP3 inflammasome activation in monocytes from a small cohort of CMML patients, and some patients produced high levels of IL-1β and some patients produced low levels of IL-1β compared with older healthy donors. Intriguingly, CMML patients with heightened NLRP3 activation showed increased treatment dependency and disease severity. Collectively, our results suggest that aging causes increased sensitivity to NLRP3 inflammasome activation at a cellular level, which may explain increased inflammation and immune dysregulation in older individuals. Furthermore, NLRP3 inflammasome activation was dysregulated in a small cohort of CMML patients and was positively correlated with disease severity.

LRR-protein RNH1 dampens the inflammasome activation and is associated with COVID-19 severity

RNH1 prevents inflammation by inhibiting inflammasome activation through controlling caspase-1 protein levels. In COVID-19 patients, RNH1 expression levels were negatively associated with disease severity and inflammation, suggesting a role for RNH1 in SARS-CoV-2–mediated inflammation and pathology.

Inflammasomes are cytosolic innate immune sensors of pathogen infection and cellular damage that induce caspase-1–mediated inflammation upon activation. Although inflammation is protective, uncontrolled excessive inflammation can cause inflammatory diseases and can be detrimental, such as in coronavirus disease (COVID-19). However, the underlying mechanisms that control inflammasome activation are incompletely understood. Here we report that the leucine-rich repeat (LRR) protein ribonuclease inhibitor (RNH1), which shares homology with LRRs of NLRP (nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain containing) proteins, attenuates inflammasome activation. Deletion of RNH1 in macrophages increases interleukin (IL)-1β production and caspase-1 activation in response to inflammasome stimulation. Mechanistically, RNH1 decreases pro-IL-1β expression and induces proteasome-mediated caspase-1 degradation. Corroborating this, mouse models of monosodium urate (MSU)-induced peritonitis and lipopolysaccharide (LPS)-induced endotoxemia, which are dependent on caspase-1, respectively, show increased neutrophil infiltration and lethality in Rnh1^−/− mice compared with wild-type mice. Furthermore, RNH1 protein levels were negatively related with disease severity and inflammation in hospitalized COVID-19 patients. We propose that RNH1 is a new inflammasome regulator with relevance to COVID-19 severity.

Parentally inherited long non-coding RNA Cyrano is involved in zebrafish neurodevelopment

Transfer of genetic material from parents to progeny via fusion of gametes is a way to ensure flow of information from one generation to the next. Apart from the genetic material, gametes provide a rich source of other factors such as RNA and proteins which can control traits of the embryo. Non-coding RNAs are not only carriers of regulatory information but can also encode memory of events of parental life. Here, we explore the possibility of parental inheritance of non-coding RNAs, especially long non-coding RNAs. Meta-analysis of RNA-seq data revealed several non-coding RNAs present in zebrafish oocyte, sperm and 2cell-stage. The embryo is transcriptionally silent at this stage, we rationalize that all the RNAs detectable at 2cell-stage are deposited either by sperm or oocyte or both and thus inherited. In the inherited pool, we noticed a conserved lncRNA, Cyrano previously known for zebrafish brain development. Knockdown of inherited Cyrano by miR-7 without changing zygotic Cyrano altered brain morphology at 24 hpf and 48 hpf. This defect could be partially rescued by injecting full length Cyrano lncRNA or a mutant resilient to knock-down by miR-7. In future, there is ample scope to check the possibility of inherited lncRNAs as carriers of memory of parental life events and building blocks that set up an initial platform for development.

A Simple Alternative to Stereotactic Injection for Brain Specific Knockdown of miRNA

MicroRNAs (miRNAs) are key regulators of gene expression. In the brain, vital processes like neurodevelopment and neuronal functions depend on the correct expression of microRNAs. Perturbation of microRNAs in the brain can be used to model neurodegenerative diseases by modulating neuronal cell death. Currently, stereotactic injection is used to deliver miRNA knockdown agents to specific location in the brain. Here, we discuss strategies to design antagomirs against miRNA with locked nucleotide modifications (LNA). Subsequently describe a method for brain specific delivery of antagomirs, uniformly across different regions of the brain. This method is simple and widely applicable since it overcomes the surgery, associated injury and limitation of local delivery in stereotactic injections. We prepared a complex of neurotropic, cell-penetrating peptide Rabies Virus Glycoprotein (RVG) with antagomir against miRNA-29 and injected through tail vein, to specifically deliver in the brain. The antagomir design incorporated features that allow specific targeting of the miRNA and formation of non-covalent complexes with the peptide. The knock-down of the miRNA in neuronal cells, resulted in apoptotic cell death and associated behavioural defects. Thus, the method can be used for acute models of neuro-degeneration through the perturbation of miRNAs.