The Impact of SOCS1 and SOCS3 Peptide Mimetics on RHO and CDC42 Proteins Expression, F-actin Cytoskeleton Rearrangements, and Cytokines Production of Uninfected and HSV-1 Infected M1 and M2 RAW 264.7 Murine Macrophages
Nancy Bigley (Committee Chair), Barbara Hull (Committee Member), Dawn Wooley (Committee Member)
Master of Science (MS)
The immune system plays an essential role in the pathogenesis of HSV-1 during the lytic phase of the disease, orchestrating the inflammatory response, retaining the virus in its latent phase and preventing the recurrence of HSV-1 infection. Macrophages display a vital role in the innate and adaptive immune responses during multiple phases of HSV-1 infection. Polarized macrophages are categorized into two distinct classes with diverse functions. The classically activated M1 can engulf and destroy the microbial agents, produce proinflammatory cytokines, and participate in the pathogenesis of many inflammatory diseases. The alternatively activated M2 induces anti-inflammatory mediators and stimulates tissue remodeling and wound healing. The reorganization of filamentous actin is a prerequisite for polarized macrophages functions. Rho and Cdc42 are highly expressed Rho GTPase proteins in Raw 264.7 murine macrophages. Rho and Cdc42 proteins play a critical role in altering the organization of structural networks of actin microfilaments. These GTPases are cycling between an active (GTP bound) and inactive (GDP bound) form. Activation of Rho proteins leads to dynamic changes in macrophage's cytoskeleton, cell migration, and phagocytic function. SOCS1 and SOCS3 are structurally related proteins that are induced endogenously in macrophages. They are involved in the down-regulation of the JAK-STAT pathways that lead to production of inflammatory cytokines. The present study indicated that SOCS1 challenged M1 macrophages expressed lower levels of Cdc42 and Rho A proteins and higher level of F- actin in the presence or absence of HSV-1. SOCS1 challenged M1 also exhibited significant reduction in TNF-a production and percentage of viable cells. This study also indicated that SOCS1 challenged M2 polarized macrophages did not show change levels of Cdc42 and Rho proteins and F-actin staining intensities from that of unchallenged M2 cells. These cells expressed a significant increase in IL-10 as compared to unchallenged M2 cells. In contrast, this study demonstrated that SOCS3 has a transient effect on M1 and M2 polarized cells in the early hours of infection. At 2, 4, and 6 hours of infection, SOCS3 potentiated the effect of M1 by promoting the activation of Rho GTPase proteins, and increasing proinflammatory TNF-a cytokine secretion. On the other hand, SOCS3 challenged M2 cells expressed a significant increase in levels of RhoA and Cdc42 proteins. They also showed a significant decrease in F actin staining intensity and IL-10 secretion compared to unchallenged cells. SOCS3 effects on polarized macrophages disappeared at late (24 and 48) hours. This data suggests that during an active infection, SOCS1 regulates M1-macrophages indirectly by constraining the activation of Cdc42 and Rho GTPase proteins. This hinders their intracellular signaling pathways and impacts F-actin organization which can interfere with the phagocytic properties of macrophages. During the resolution phase of infection, SOCS1 upregulates M2 polarization and potentiates the M2 secretion of IL-10. SOCS3 has a transient effect on M1 and M2 cells in the early hours of infection. SOCS3 potentiates the effect of M1 cells, promotes the activation of Rho GTPase proteins, and increases proinflammatory cytokine secretion. SOCS3 downregulated M2 cell function that may help to make M1 more efficient, favoring the inflammatory process to eliminate invading pathogens. During the resolution phase of infection, SOCS3 may display an endogenous regulation role in macrophages through the activation of the JAK-STAT3-IL10 pathway.
Department or Program
Microbiology and Immunology
Year Degree Awarded
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