Date of Award

Spring 2020

Document Type

Open Access Dissertation


Biomedical Engineering

First Advisor

Mitzi Nagarkatti

Second Advisor

Prakash Nagarkatti


Staphylococcal enterotoxin B (SEB) is a highly potent CDC select agent that can trigger acute lung injury (ALI) via robust T cell proliferation and differentiation, and massive cytokine and chemokine release. Δ9-Tetrahydrocannabinol (THC) is a psychoactive ingredient found in Cannabis sativa. In the current study, we investigated the effects of treatment with THC on SEB-induced acute lung injury. To this end, acute lung injury was induced by a dual dose of SEB in C3H/HeJ mice, which were then treated with vehicle or THC. THC-treatment led to survival of all the SEB-administered mice when compared to vehicle-treated. This corroborated with THC-induced decrease in the T lymphocyte cells in the lungs and increase in the number of myeloid-derived suppressor cells and Treg. In addition, THC induced a significant decrease in the proinflammatory cytokines and chemokines in BALF and serum, In order to determine the epigenetic mechanisms underlying THC-induced beneficial effects, we performed high-throughput microRNA (miR) microarrays with lung mononuclear cells (MNC) from vehicle and THC-treated SEB-administered mice. Our data showed dysregulation in the expression of several miRs in these groups. Transcriptome array analysis showed THC induced the dysregulation of several genes in the epithelial cells and MNC from ALI mice, and some of dysregulated genes were particularly related to antimicrobial enzymes and peptides, tight junction proteins and mucins. Pyrosequencing analysis discovered that THC dramatically altered microbiota in the lung, colon and blood of ALI mice. Furthermore, beneficial bacterial species such as Ruminococcus gnavus could produce beneficial short-chain fatty acids such as propionic acid, butyric acid and acetic acid. Also, we found that treatment of mice with THC after SEB injection led to attenuation of SEB-induced lung inflammation through induction of immune cell apoptosis and suppression of T cell proliferation. Interestingly, single cell RNA sequencing from lungs showed that THC treatment induced pro-apoptotic genes. In addition, metabolomics analysis revealed elevated concentrations of apoptosis-related amino acids propionyl L- carnitine. Moreover, metabolic assays in SEB-activated T cells demonstrated that THC promotes a shift from dependency on glucose oxidation to fatty acid oxidation. Collectively, this study demonstrates that THC treatment alleviates SEB-induced ALI.