<p>Neutrophils are the first cells recruited to an immune
stimulus stemming from infection or sterile injuries via a mixture of
chemoattractant cues. In addition to eliminating pathogens, neutrophils
coordinate the overall inflammation by activating and producing inflammatory
signals in the tissue while modulating the activation of other immune cells
which in some cases leads to adverse tissue damage. Over amplified or chronic
neutrophil recruitment directly leads to autoimmune diseases including
rheumatic arthritis, diabetes, neurodegenerative diseases, and cancer.
Dampening neutrophil recruitment is a strategy to intervene in
neutrophil-orchestrated chronic inflammation. Despite intensive research over
the past several decades, clinical studies targeting neutrophil migration have
been largely unsuccessful, possibly due to the prominent redundancy of adhesion
receptors and chemokines. Additional challenges lie in the balance of dampening
detrimental inflammation while preserving immunity. Neutrophils are terminally
differentiated cells that are hard to study in cell culture. Mouse models are
often used to study hematopoiesis, migration, and chemotaxis of neutrophils but
is very labor intensive. To discover novel therapeutic targets that modulate
neutrophil migration, we performed a neutrophil-specific microRNA (miRNA)
overexpression screen in zebrafish and identified eight miRNAs as potent
suppressors of neutrophil migration. We have generated transgenic zebrafish
lines that overexpresses these candidate miRNAs where we recapitulated the
mitigation in neutrophil motility and chemotaxis to tissue injury or infection.
Among those we further characterized two miRNAs which have not been reported to
regulate neutrophil migration, namely miR-722 and miR-199.</p>
<p> </p>
<p>MiR-722 downregulates the transcript level of <i>rac2</i> through binding to the <i>rac2</i> 3'UTR. Furthermore, miR-722-overexpressing
larvae display improved outcomes in both sterile and bacterial systemic models,
which correlates with a robust upregulation of the anti-inflammatory cytokines
in the whole larvae and isolated neutrophils. miR-722 protects zebrafish from lethal lipopolysaccharide
challenge. In addition, overexpression of mir-722 reduced chemotaxis of human
neutrophil like cells, indicating that miR-722
is a potential agent to reduce inflammation in humans. </p>
<p>MiR-199<i>,</i> decreases neutrophil chemotaxis in zebrafish
and human neutrophil-like cells. Intriguingly, in terminally differentiated
neutrophils, miR-199 alters the cell cycle-related pathways and
directly suppresses cyclin-dependent kinase 2 (<i>cdk2</i>), whose known
activity is restricted to cell cycle progression and cell differentiation.
Inhibiting Cdk2, but not DNA replication, disrupts cell polarity and chemotaxis
of zebrafish neutrophils without inducing cell death. Human neutrophil-like
cells deficient in CDK2 fail to polarize and display altered signaling
downstream of the formyl peptide receptor. Chemotaxis of primary human
neutrophils is also reduced upon CDK2 inhibition. Furthermore, miR-199 overexpression
or CDK2 inhibition significantly improves the outcome of lethal systemic
inflammation challenges in zebrafish. </p>
<p> </p>
<p>In summary, our results reveal previously unknown functions
of these miRNAs, and
provide potential avenues to modulate neutrophil migration as well as lead to
discoveries of novel factors which can regulate this process. We have also
discovered a non-classical role of CDK2 in regulating neutrophil migration
which provides directions for alleviating systemic inflammation and a better
understanding of neutrophil biology. </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12397841 |
| Date | 09 September 2022 |
| Creators | Alan Y Hsu (8912033) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/Identification_and_characterization_of_microRNAs_which_moderate_neutrophil_migration_and_acute_inflammation/12397841 |
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