# How Does Nicotine Impair Macrophage Killing of Mycobacterium Tuberculosis?

> **NIH VA I01** · VA EASTERN COLORADO HEALTH CARE SYSTEM · 2020 · —

## Abstract

Nicotine at physiologic concentrations impairs macrophage killing of Mycobacterium tuberculosis (MTB),
resulting in a 2-5 fold increase in bacterial burden. We have also found that preventing nicotine binding –
either pharmacologically or by genetic disruption of the nicotinic receptor – significantly mitigated cigarette
smoke extract-induced impairment of macrophage killing of MTB. But the mechanisms by which nicotine
impairs macrophage control of MTB are not known. Our hypothesis is that nicotine sabotages macrophage
function against MTB (i) directly through NFκB-mediated inhibition of autophagy and apoptosis as well as
through DICER/microRNA-mediated inhibition of host-protective cytokine production and (ii) indirectly through
increased production of CTLA-4 and activation of T regulatory cells (Tregs).
Aim 1: Determine the mechanisms by which nicotine directly impairs macrophage killing of MTB.
Approach: We will isolate nicotine-naïve human alveolar macrophages (AM) and monocyte-derived
macrophages (MDM), infect them with MTB ± nicotine, and quantify autophagy, apoptosis, intracellular burden
of MTB, and the extent NFκB inhibition mitigates the effects of nicotine. We will also knockdown specific NFκB
subunits and DICER to determine their roles in nicotine-mediated inhibition of anti-MTB immunity. Hypothesis:
Nicotine induction of NFκB in AM and MDM will inhibit autophagy and apoptosis, resulting in increased burden
of MTB. Inhibition of NFκB activation will abrogate these effects of nicotine and restore macrophage killing of
MTB. Knockdown of DICER will reverse the suppression of MTB-induced cytokines by nicotine.
Aim 2: Determine the mechanisms by which nicotine indirectly impairs macrophage killing of MTB.
Subaim A. An ex vivo model using primary human cells. Approach: We will culture naïve human MDM
with naïve vs. nicotine-exposed Tregs and infect the cells with MTB. To determine if CTLA-4 expression is
responsible for nicotine-induced increase in Treg activity and secondary MDM suppression, the cells will also
be incubated with anti-CTLA-4 neutralizing antibody. Hypothesis: Nicotine will increase CTLA-4 expression
on Tregs, augmenting their production of IL-10 and TGFβ. This will inhibit autophagy in MTB-infected MDM
and result in greater bacterial burden compared to MDM co-cultured with nicotine-naïve Tregs. Antagonism of
CTLA-4 will abrogate these immunosuppressive effects of nicotine.
Subaim B. In vivo murine model. Approach: We will adoptively transfer Tregs from unexposed or nicotine-
exposed B6.PL(Thy1.1) mice into Treg-depleted Foxp3+GFP+DTR+(Thy1.2) mice, infect the recipient mice with
MTB, and quantify MTB burden, macrophage and T cell phenotypes, lung histopathology, and survival.
Hypothesis: Mice receiving nicotine-exposed Tregs will have fewer host-protective M1 lung macrophages and
TH1 and TH17 cells compared to mice receiving nicotine-naïve Tregs. As a result, mice receiving nicotine-
exposed Tregs will be more susceptible t...

## Key facts

- **NIH application ID:** 9814113
- **Project number:** 5I01CX001452-03
- **Recipient organization:** VA EASTERN COLORADO HEALTH CARE SYSTEM
- **Principal Investigator:** EDWARD D CHAN
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2020
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2017-10-01 → 2021-09-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9814113

## Citation

> US National Institutes of Health, RePORTER application 9814113, How Does Nicotine Impair Macrophage Killing of Mycobacterium Tuberculosis? (5I01CX001452-03). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9814113. Licensed CC0.

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