Norepinephrine-mediated resistance to nutritional immunity in Neisseria gonorrhoeae

/ ABSTRACT Neisseria gonorrhoeae (Gc) is the bacterial pathogen responsible for the sexually transmitted infection gonorrhea, which causes an estimated 87 million cases globally each year. As cases and antibiotic resistance increase, new approaches to treat and prevent gonorrhea are high priority. Gc promotes a robust inflammatory response characterized by neutrophil recruitment. Despite this, neutrophils are insufficient to eliminate Gc. Untreated gonococcal disease can cause pelvic inflammatory disease, ectopic pregnancies, and infertility. To limit infection, the host uses nutritional immunity: sequestration of essential metals like iron from pathogens. During infection, Gc is under continual stress to acquire iron for survival and replication, but its adaptation to low- iron conditions during neutrophil challenge remains unclear. This F30 proposal is based on my discovery that while Gc does not survive in iron-limited medium, it grows in neutrophil supernatants collected in this medium. I found that neutrophils do not release iron, but rather release norepinephrine that enables Gc to overcome iron restriction. Norepinephrine is known for its role as a neuroendocrine hormone. However, it has been shown to have non-canonical roles in supporting microbial growth and virulence in other bacterial pathogens, primarily by acting as a trans-kingdom signal and/or pseudo-siderophore. While norepinephrine has been shown to strip iron from iron-sequestering proteins like transferrin, I found that norepinephrine enhanced Gc growth in protein-free media. I also found that Gc response to norepinephrine is blocked by α-adrenergic antagonist phentolamine and is independent of TonB, which powers outer membrane iron transporters. Thus, norepinephrine-enhanced Gc growth may involve mechanisms that cannot be explained by our current understanding of Gc iron acquisition. I hypothesize that Gc senses host-derived norepinephrine and responds by altering bacterial physiology to better cope with iron limitation during infection. In Aim 1, I will characterize how norepinephrine impacts iron availability in Gc by assessing changes in total iron, labile iron, and iron-dependent gene expression. This will inform our understanding of how norepinephrine changes Gc physiology to withstand iron limitation. In Aim 2, I will identify and characterize gonococcal gene product(s), including putative norepinephrine sensors, that enable Gc to respond to norepinephrine. This Aim will uncover how Gc exploits norepinephrine to resist iron starvation. Altogether, the research proposed in this F30 application will expand our understanding of how Gc senses and adapts to the inflammatory environment to overcome nutritional immunity during infection of host mucosal sites. The findings may lead to new drug and vaccine targets to combat gonococcal disease. These efforts and complementary activities planned under this award will provide me with the training and expertise to achieve my career goal of becoming a physician-scientist specializing in molecular mechanisms of microbial pathogenesis and reproductive infectious disease. Project Number: 1F30AI191666-01 | Fiscal Year: 2025 | NIH Institute/Center: National Institute of Allergy and Infectious Diseases (NIAID) | Principal Investigator: Camille Westlake | Institution: UNIVERSITY OF VIRGINIA, CHARLOTTESVILLE, VA | Award Amount: $38,945 | Activity Code: F30 | Study Section: Special Emphasis Panel[ZRG1 F07A-M (20)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1F30AI19166601