Gonzalez Ferrer, Shekina
(2024)
Bolstering the Immune System for Improved Defense Against Klebsiella pneumoniae.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Klebsiella pneumoniae (KP) are gram-negative bacteria of public health concern due to their capacity to acquire antibiotic resistance and cause deadly infections. Macrophages are crucial in the host defense against KP and understanding factors causing cellular dysfunction during severe infection is a priority. Signal transducer and activator of transcription 1 (STAT1) is a mammalian master transcription factor crucial for immune cells function. STAT1 is activated through interferon (IFN) signaling and helps defend against systemic spread of acute KP-intrapulmonary infection.
We found that in a two-hit model of an acute rise in red blood cell (RBC) engulfment by macrophages and KP-intrapulmonary infection caused dysregulated STAT1 suppression, both in vitro and in vivo. Using a mouse pneumonia model, we found that STAT1 deficiency led to an early neutrophil-dominant transcriptional profile and recruitment in the lung, followed by KP dissemination and lung injury. However, myeloid-cell STAT1 was dispensable for widespread KP control. By single cell RNA seq, KP-infected lungs of Stat1-/- mice displayed heightened CD4+T-cells at 24h and further analysis showed IL-17-producing CD4+T-cells were increased in lungs of Stat1-/- mice. Blocking global IL17-signaling led to increased KP proliferation and dissemination, while CD4+T-cell depletion reduced KP in lungs of Stat1-/- mice. These findings suggest STAT1 employs myeloid cell-extrinsic mechanisms to regulate neutrophil responses and protect against invasive KP by restricting non-specific CD4+T-cell activation in the lung.
Furthermore, we speculated that both host and pathogen factors were associated with the overall STAT1 protein degradation observed in the two-hit model of excess heme from RBC engulfment in macrophages and KP-infection. We found that STAT1 was not completely degraded through the proteasomal pathway upon KP+Hemin stimulus. Surprisingly, p62 expression, an important component of autophagy machinery formation for lysosomal degradation, was induced upon macrophage stimulation with KP, but hemin failed to suppress p62, while IRF1 (a downstream effector of STAT1) remained suppressed. Moreover, we noted variability of STAT1 protein expression in macrophages upon excess hemin challenge with different KP capsule-type strains. Overall, these findings suggest STAT1’s degradation through alternative mechanisms during oxidative stress from exposure to KP+Hemin along with the complex regulation of STAT1 during KP-infection.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
| Title | Member | Email Address | Pitt Username | ORCID |
|---|
| Committee Chair | Gottschalk, Rachel | | | | | Committee Member | Shanks, Robert | | | | | Committee Member | Lee, Nara | | | | | Committee Member | Lee, Janet | | | | | Thesis Advisor | Van Tyne, Daria | | | |
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| Date: |
14 October 2024 |
| Date Type: |
Publication |
| Defense Date: |
5 June 2024 |
| Approval Date: |
14 October 2024 |
| Submission Date: |
21 July 2024 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
158 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
School of Medicine > Microbiology and Immunology |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
STAT1 |
| Related URLs: |
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| Date Deposited: |
14 Oct 2024 15:44 |
| Last Modified: |
14 Oct 2024 15:44 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/46709 |
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