Abstract

The safety concerns regarding the unwanted side effects of Δ9-THC as a psychoactive agent preclude its widespread use in the clinic. Our project targets the psychoactive Δ9-THC and aims to alarm “vaccinators” of cannabis intake and convert Δ9-THC into non-psychoactive substance. Thus, we have engineered E.coli substrain Nissle 1917 to sense Δ9-THC at the cell membrane via the Pmr system, and immediately secrete C-Phycocyanin as a reporter protein. At the same time the engineered bacteria can synthesize and secrete CYP2C9, CYP2C19 and UGT1A3, a series of enzymes to degrade Δ9-THC into cannabinoid glucuronic acid. In general, we have constructed a comprehensive THC detection-degradation system targeting unintentional cannabis ingestion, addiction control of certain part of the population in case of drug abuse.

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The Problem

What is Cannabis?

Cannabis is a psychoactive, addictive and hallucinogenic soft drug (with mental dependence, but not physical dependence) made from cannabis plants for smoking and considered as a medical drug in countries where it has been legalized as a medicine that is made by drying the flowers and trichomes of the female cannabis plant. The main addictive ingredient is tetrahydrocannabinol (Δ9-THC).

The use of Cannabis often produces a variety of psychological and physiological responses, such as euphoria and excitement, changes in sensory awareness, and increased appetite. And the short-term side effects includes short-term memory loss, dry mouth, impaired motor function, red eyes, paranoia, or feelings of anxiety. Long-term use can lead to marijuana addiction, long-term use by adolescence can lead to reduced mental capacity, and long-term use during pregnancy can lead to behavioral problems in children. Moreover, studies have found a strong association between Cannabis use and the risk of neurological disease, but the causality remains controversial.

What is the controversy regarding legalization of Cannabis?

For 5 millennia, Cannabis has been used throughout the world medically, recreationally, and spiritually. In 2020, the United Nations officially recognized the medical use of cannabis, it allows for much needed research on the pharmacokinetics and pharmocology of medical cannabis. However, Legalization of cannabis has a considerable controversy on the impact on public health as an extraordinarily high risk of drug abuse.

Medical and recreational Cannabis users differ in how they use the drug, the amount of the drug used and goals of ingestion. The fundamental motivation (symptom relief) of the former does not match the goal (getting high) of the latter. In other words, side effects that can limit use in a medical setting (short-term memory disruption, a sense of slowed time, increased body awareness, reduced ability to focus, incoordination, and sleepiness) are exactly the sensations recreational users prize.

Nonetheless, several studies have demonstrated significant overlap between medical users and recreational users. Many medical users continue and endorse recreational use. And this group, compared to exclusively medicinal users with similar symptom severity, endorse higher levels of problematic use, greater substance use in general, and more common use of cannabis for management of psychiatric disorders,. This particular subgroup of individuals, who use cannabis for both positively and negatively reinforcing purposes, warrant special attention in clinical practice and future research in the post-legalization period in many countries ^[1].

How does human body metabolizes Δ9-THC?

The main route of entry into the body for cannabis-type substance is by aspiration, followed by oral administration and intravenous injection are extremely rare. The main psychoactive component of cannabis, Δ9-THC, is rapidly metabolized in the liver and other tissues after it enters the body, mainly by the P450 enzyme 2C9 and the isoenzyme 2C19, into several different phase I metabolites, including 11-hydroxy-tetrahydrocannabinol (11-hydroxy-Δ9-THC, 11-OH-THC) and tetrahydrocannabin acid (11-nor-9-THC, THC-COOH). 11-OH-THC has the same psychoactive properties as Δ9-THC, while THC-COOH does not. Subsequently, part of the phase I metabolite then undergoes phase II metabolism via uridine diphosphate glucuronase (UGT) to form a glucuronide conjugate (11-nor-9-carboxy-∆9-THC glucuronide, THCCOOH-glucuronide)^[2].

Conclusion

According to the rapid spread of cannabis after legalization and the inadequate of society's response to the spread of cannabis, a new solution is needed to protect people who don't take it on their own initiative from the negative consequences brought by THC.

Our Solution

To alarm users of cannabis intake and protect them from cannabis addiction, we developed a new type of intestinal colonization engineered bacteria with Escherichia coli substrain Nissle 1917 as the chassis. We introduced the reconstructed PmrA/B system to detect THC, C-Phycocyanin as a reporter protein, and a prokaryotic THC-degradation mechanism (CYP2C9, CYP2C19 and UGT1A3 enzymes)^[3].

And to ensure biosafety, we use two safety modules to realize control of engineered bacteria. One is introducing arabinose-induced suicide mechanism to ensure users can stop the growth of our engineered bacteria at any time. The other one is adding a temperature-controlled suicide switch at 37 °C to prevent the dispersal of engineered bacteria into the natural environment.

Our Inspiration

To come up with a project idea, we started brainstorming in March about topics ranging from polyketone to panda protection. And after 3 months of deliberation, we noticed the drug addiction phenomenon. Meanwhile, the increasing medical use of cannabis, its legalization in many countries and hot controversy associated with its use drew our attention. With In-depth research, we chose this problem as our topic.

Key Value

Learn more about our project

References

1. Wilkinson ST, Yarnell S, Radhakrishnan R, Ball SA, D’Souza DC. Marijuana Legalization. Impact on Physicians and Public Health. Annu Rev Med. 2016;67:453-466. Doi:10.1146/annurev-med-050214-013454.
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2. Volkow ND, Baler RD, Compton WM, Weiss SR. Adverse health effects of marijuana use. N Engl J Med. 2014 Jun 5;370(23):2219-27. Doi: 10.1056/NEJMra1402309. PMID: 24897085; PMCID: PMC4827335.
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3. Wolf LA, Perhats C, Clark PR, Frankenberger WD, Moon MD. The perceived impact of legalized cannabis on nursing workload in adult and pediatric emergency department visits: A qualitative exploratory study. Public Health Nurs. 2020;37(1):5-15. doi:10.1111/phn.12653
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