Effects and mechanisms of cold-induced stress on the development of Chlamydia muridarum genital infection in a mouse model

Program Director/Principal Investigator (Last, First, Middle): Belay, Tesfaye
Project Summary
Chlamydia trachomatis genital infection is the most common sexually-transmitted bacterial disease in the world. If left
untreated, chlamydia genital infection leads to pelvic inflammatory disease, ectopic pregnancy, and infertility. It is widely
known that the immunopathological reactions to this disease, rather than the infection itself, remain a serious public health
problem. There is medical interest in understanding how stress may impact resistance or susceptibility to sexually
transmitted diseases. Many investigators have examined the immunological responses to C. trachomatis, but the effect of
stress on chlamydia genital infection has not yet been explored and is not understood. Our research seeks to understand the
relationship between them. To accomplish this, we have developed a chronic-stress model in mice by daily immersing mice
in cold water for five minutes daily for 21 days. This cold-induced stress (CIS) mouse model shows the increased intensity
of Chlamydia muridarum genital infection, which is associated with the elevation of the stress hormone norepinephrine
(NE) during both primary and secondary infections. Our research has demonstrated that CIS promotes increased beta2-
adrenergic receptor (β2-AR) expression in CD4 + T cells, as well as T helper 2 (Th2) differentiation, specifically by
increasing the expression of GATA-3 and IL-4 secretion. Moreover, we showed that β1/β2-AR KO are less susceptible to
C. muridarum genital infection than the WT C57BL/6J. Those observations prompted us to use a β2-AR KO model and
explore the immunopathogenesis of chlamydia genital infection. We recently found that the β2-AR KO is more resistant to
C. muridarum than the WT C57BL/6J. However, the underlying mechanisms of chronic CIS on the infection and the
immunopathogenesis in our mouse model remain unknown. The central objective of this proposal is to define the
mechanism(s) by which stress may suppress the immune system and increase the intensity of genital C. muridarum
infection and its immunopathologies in mice. We hypothesize that the NE produced by CIS leads to stimulation of the
𝛽𝛽2-AR signaling pathway in mice which, in turn, suppresses the protective immune response against C. muridarum genital
infection. To test this hypothesis, we will conduct the following three experiments as part of this project: In Aim #1, we
will compare the CD4+ T cell subset immune responses of stressed β2-AR-/- mice and C57BL/6J (β2-AR+/+) mice. We
anticipate that the deficiency of β2-AR enhances the restoration of Th1 cytokine production in stressed mice, which may
result in the clearance of C. muridarum. In Aim #2, we will explore the downstream signaling pathways from the β2-AR of
stressed KO mice compared to stressed C57BL/6J mice. Data obtained may provide insight into the involvement of β2-AR
in cAMP-protein kinase A (PKA) and mitogen-activated protein kinase (MAPK) pathways in suppressing the immune
system. In Aim#3, we will assess the histopathological changes of stressed β2-AR KO as compared to WT C57BL/6J mice,
and we will then evaluate the contributions of cytokines to pathology. Data from this method will demonstrate a reduced
oviductal pathology in β2-AR KO mice. The proposed experiments will provide insight into the immunosuppression
mechanisms resulting from the interactions of the endocrine and immune systems in the immunopathogenesis of chlamydia.
Overall, results obtained from these β2-AR deficient mice, combined with our previous findings and those of others, could
reveal more evidence of the effects of chronic stress on the severity of chlamydial disease in humans.
OMB No. 0925-0001/0002 (Rev. 03/2020 Approved Through 02/28/2023) Page Continuation Format Page

Grant Number: 1R15AI174169-01A1
NIH Institute/Center: NIH
Principal Investigator: Tesfaye Belay