Scientists are looking at the possibility of using some antidepressant drugs to help treat a wide range of infectious diseases.

Researchers at the Virginia Commonwealth University and other organizations examined the impact of a certain type of antidepressants known as functional inhibitors of acid sphingomyelinas, or FIASMAs. These drugs include amitriptyline, desipramine, and nortriptyline.

Results showed that FIASMAs are capable of preventing the growth or outright killing at least four different kinds of intracellular bacterial pathogens found in animal models and tissue cell culture.

"Antibiotic options for diseases caused by intracellular bacteria are limited because many of these drugs cannot penetrate our cell membranes," said Jason Carlyon, a professor from VCU's Microbiology and Immunology Department and lead investigator of the study. "In essence, the bacteria are protected."

Antibiotic Treatment For Bacterial Infections

Infections caused by intracellular bacteria are usually treated using tetracyclines. These antibiotics are capable of penetrating cell membranes and attacking the microbes directly.

However, not all patients can receive tetracycline treatment since it can cause some allergic reactions. The drug can also result in adverse side effects in children and pregnant women.

Studies have also identified cases of antibiotic resistance related to intracellular bacterial infections.

Carlyon highlighted the need for a new class of drugs that can treat patients who are not able to receive tetracycline therapy. Such medications can be used either as an alternative to antibiotics, or even as a partner treatment to help augment the impact of antibiotics.

He added that these drugs could be used for infections that require prolonged antibiotic therapies such as those caused by Coxiella burnetti and Chlamydia pneumoniae bacteria.

Potential Of FIASMAs To Treat Infections

In their study, Carlyon and his team collaborated with colleagues from other organizations such as the University of Arkansas for Medical Sciences, Indiana University Medical Center, University of Nebraska Medical Center, and the University of South Florida. Their work focused on how FIASMAs target and kill different intracellular bacteria.

The researchers tested the impact of FIASMA on four species of bacteria:

  • Human granulocytic anaplasmosis - A tick-borne infection that targets the body's white blood cells known as neutrophils.

  • Q fever - A disease caused by the Coxiella burnetii bacteria and known to transfer from animals to humans.

  • Two kinds of chlamydia infections.

Carlyon and his colleagues observed how FIASMAs can affect cholesterol, an important nutrient used by intracellular pathogens, traffics inside cells to disrupt the access of bacterial to certain lipids. They also saw how such antidepressants can prevent anaplasmosis in both mice and tissue culture samples.

The researchers then tested FIASMA treatment on Coxiella burnetii, a primary agent of Q fever infection, and found how the antidepressants ultimately killed the microbe. The medication also partially inhibited the spread of chlamydial infections in cell culture.

Carlyon explained that since FIASMAs can disrupt the trafficking of cholesterol in cells and cholesterol plays a key role in different facets of human biology, the antidepressants have been used to address a wide range of medical conditions and diseases.

He pointed out that FIASMAs can target intracellular cholesterol, which removes the need for treatments to directly attack bacteria.

The class of drugs that the researchers evaluated was able to target an enzyme in cells known to regulate cholesterol and not the bacterial itself.

The team does not see the pathogens being able to develop some form of resistance to FIASMAs since the treatment targets a pathway that the microbes depend on to survive while inside their host's body.

The findings of the multi-organizational study are featured in the journal Life Science Alliance.

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