Targeting a chronic pain gateway could bring relief

August 19, 2020

Something like a quarter of the world's population suffers from chronic pain at some point in their lives. As opposed to acute pain - for example, the feeling after hitting your finger with a hammer - chronic pain may not even have a clear cause, and it can linger for years or lifetimes. The burden of chronic pain includes damage to mental and physical health, lower productivity and drug addiction. A new study led by scientists at the Weizmann Institute of Science suggests an original approach to treating this affliction, by targeting a key gateway leading to the activation of genes in the peripheral nerve cells that play a role in many forms of chronic pain. The findings of this study were published today in Science.

Pain starts in the sensory neurons - those that pass information from the skin to the central nervous system. Damage to these neurons, chronic injury or disease can cause the neurons to "short circuit," sending continuous pain messages. Prof. Mike Fainzilber of the Institute's Biomolecular Sciences Department investigates molecules that regulate the biomolecular messaging activities taking place within these nerve cells. These molecules - importins - are found in every cell, acting as conduits between the cell nucleus and its cytoplasm, shuttling molecules in and out of the nucleus and thus controlling access to the genes. This role takes on special significance in the peripheral nerve cells, with their long, thin bodies in which molecular messages can take hours to get from nerve endings to cell nuclei. Some of the importins Fainzilber and his team have identified, for example, relay messages about injury to the body of the nerve cell, initiating repair mechanisms.

To ask whether importins are involved in chronic neuropathic pain, the researchers, led by Dr. Letizia Marvaldi in Fainzilber's group, first set out to screen a number of importin-mutant mouse lines generated by the lab of Prof. Dr. Michael Bader at the Max-Delbruck Center in Berlin, who collaborated in this research. The research was supported by the European Research Council.

Behavioral screens on these different lines revealed a particular importin - importin alpha-3 - as the only importin implicated in controlling pain pathways. The team then sought to identify the gene expression pattern associated with long-lasting pain in peripheral nerve cells, and see how it tied into importin alpha-3 activity. Analyses of differences in the expression patterns between normal neurons and neurons lacking importin alpha-3 directed Dr. Marvaldi's attention to c-Fos, a protein that importin alpha-3 brings into the nucleus. c-Fos is a transcription factor - a molecule that raises or lowers the expression of numerous genes. Further experiments in mice showed that c-Fos accumulates in the nucleus in peripheral nerve cells of mice suffering from chronic pain.

They then used specialized viruses as tools to reduce or disable importin alpha-3 or c-Fos in mouse peripheral nerve cells. These mice had much reduced responses to chronic pain situations than those of regular mice. Further research showed that importin alpha-3 is critical in late and chronic pain. c-Fos is also involved in earlier pain responses, but it seems to enter the nucleus by other means at those earlier stages. This suggests that blocking importin alpha-3 activity might be especially well-suited to preventing lasting, chronic pain.

The research team then took their findings to the next level, asking how easily they can be translated to clinical application. They took advantage of a specialized database, the Connectivity Map (CMap) from the Broad Institute in Massachusetts, which reveals connections between drugs and gene expression patterns. This database enabled them to identify around 30 existing drugs that might target the importin alpha-3-c-Fos pathway. Almost two thirds of compounds they identified were not previously known to be associated with pain relief. The team chose two - one a cardiotonic drug and the other an antibiotic - and tested them again in mice. Indeed, injection with these compounds provides relief of neuropathic pain symptoms in mice.

"The compounds we identified in this database search are a kind of fast track - proof that drugs already approved for other uses in patients can probably be repurposed to treat chronic pain," says Marvaldi. "Clinical trials could be conducted in the near future, as these compounds have already been shown to be safe in humans."

"We are now in a position to conduct screens for new and better drug molecules that can precisely target this chain of events in the sensory neurons," says Fainzilber. "Such targeted molecules might have fewer side effects and be less addictive than current treatments, and they could provide new options for reducing the burden of chronic pain." Also participating in this research were Dr. Nicolas Panayotis, Dr. Stefanie Alber, Dr. Shachar Y. Dagan, Dr. Nataliya Okladnikov, Dr. Indrek Koppel, Agostina Di Pizio, Didi-Andreas Song, Yarden Tzur, Dr. Marco Terenzio, Dr. Ida Rishal and Dr. Dalia Gordon, all of the Weizmann Institute of Sciences Biomolecular Sciences Department; Dr. Franziska Rother of the Max-Delbruck Center, Berlin and the University of Lübeck, Germany; and Prof. Dr. Enno Hartmann of the University of Lübeck.
-end-
Prof. Michael Fainzilber's research is supported by the Moross Integrated Cancer Center; the David Barton Center for Research on the Chemistry of Life; the Nella and Leon Benoziyo Center for Neurological Diseases; the Laraine and Alan A. Fischer Laboratory for Biological Mass Spectrometry; the Dr. Miriam and Sheldon G. Adelson Medical Research Foundation; the Rising Tide Foundation; Lawrence Feis; the estate of Florence and Charles Cuevas; the estate of Lilly Fulop; the estate of Lola Asseof; and the European Research Council. Prof. Fainzilber is the incumbent of the Chaya Professorial Chair in Molecular Neuroscience.

The Weizmann Institute of Science in Rehovot, Israel, is one of the world's top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.

Weizmann Institute of Science

Related Neurons Articles from Brightsurf:

Paying attention to the neurons behind our alertness
The neurons of layer 6 - the deepest layer of the cortex - were examined by researchers from the Okinawa Institute of Science and Technology Graduate University to uncover how they react to sensory stimulation in different behavioral states.

Trying to listen to the signal from neurons
Toyohashi University of Technology has developed a coaxial cable-inspired needle-electrode.

A mechanical way to stimulate neurons
Magnetic nanodiscs can be activated by an external magnetic field, providing a research tool for studying neural responses.

Extraordinary regeneration of neurons in zebrafish
Biologists from the University of Bayreuth have discovered a uniquely rapid form of regeneration in injured neurons and their function in the central nervous system of zebrafish.

Dopamine neurons mull over your options
Researchers at the University of Tsukuba have found that dopamine neurons in the brain can represent the decision-making process when making economic choices.

Neurons thrive even when malnourished
When animal, insect or human embryos grow in a malnourished environment, their developing nervous systems get first pick of any available nutrients so that new neurons can be made.

The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.

Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.

How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.

A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.

Read More: Neurons News and Neurons Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.