Detection of Monoamine Mediated Immune Cell Communication by Nanosensors
by Meshkat Dinarvand
Date of Examination:2021-11-15
Date of issue:2022-11-11
Advisor:Prof. Dr. Sebastian Kruss
Referee:Prof. Dr. Sebastian Kruss
Referee:Prof. Dr. Jörg Enderlein
Persistent Address:
http://dx.doi.org/10.53846/goediss-9535
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Abstract
English
The immune system comprises many organs, organ systems, cell types and secretory components that together form an intricate host defense network encompassing physical, biological and chemical barriers. Secretory components of the immune system play an important role in modulating the immune response. In this dissertation, I focus on monoamine mediators, predominantly involved in the nervous and endocrine systems, as modulators of the immune system. Immune cells do not function independently and homogenously; their activity is modulated by their microenvironment which is controlled by the composition of the inflammatory mediators. Therefore, immune cells tune their activity according to their spatial condition. The complexity and flexibility of the immune response compels researchers to investigate dynamics of exocytosis from immune cells with novel detection systems. Conventional analytical tools often lack spatial resolution to detect release events from cells simultaneously and identify localized regions where exocytosis occurs. In this dissertation, a novel fluorescent nanosensor based on single-walled carbon nanotubes (SWCNTs) is designed to detect release of monoamines from neutrophils and platelets with high spatiotemporal resolution in the near infrared (980 nm) region. This study provides new information regarding monoamine exocytosis from immune cells. Initially, a near infrared SWCNT sensor was designed to detect exocytosis of serotonin from human platelets. The selectivity, specificity and reversibility of the sensor was demonstrated. The nanosensor had a Kd value of 301 nM ± 138 nM. Then, a paracrine immune modulation involving platelet-derived serotonin and dopamine exocytosis from neutrophils was discovered. We observe that the entire dopaminergic machinery (tyrosine hydroxylase, dopamine transporter, dopamine receptors, vesicular monoamine transporter) is expressed and functionally active in neutrophils. Exocytosis was investigated with fluorescent false neurotransmitters. Serotonin induced dopamine exocytosis following Ca2+ mobilization in neutrophils. Dopamine exocytosis was detected with our nanosensors and we showed that upon neutrophil-platelet interaction, stimulated platelets induced dopamine release from neutrophils. Finally, the immunomodulatory role of dopamine was studied and we discovered dopamine suppressed NETosis, an important host defense strategy of neutrophils, in a receptor-mediated and concentration dependent manner. In summary, the development of novel fluorescent probes/sensors for neurotransmitters enabled imaging with unprecedented spatiotemporal resolution and identification of a new role of neurotransmitters in the immune system.
Keywords: Nanotubes; Nanosensors; Immune cells; Dopamine; Near-infrared Fluorescence; Biosensors