Amyotrophic lateral SCLEROSIS: The promise of gene silencing

This new therapy for injecting into the spinal cord an RNA that blocks the gene responsible for the disease, has just prevented the occurrence of amyotrophic lateral sclerosis (ALS) in an animal model of the disease carrier of the responsible mutated gene. In addition, this treatment candidate blocked the progression of ALS in animals that had already developed symptoms of the disease. Very promising results, delivered by a team from the University of California San Diego, in the journal Nature Medicine.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that affects nerve cells in the brain and spinal cord: the motor neurons responsible for movement communication are specifically affected, with a progressive loss of muscle control affecting the ability to speak, eat, move and breathe. While there are symptomatic treatments for ALS, there is currently no cure. The majority of patients succumb to the disease 2 to 5 years after diagnosis. There are 2 types of ALS:

sporadic: this is the most common form, accounting for 90 to 95% of cases;
family, 5 to 10% of cases.
Previous research has shown that at least 200 mutations in the SOD1 gene are linked to the development of ALS.

The prospect of an effective therapy, “the most powerful ever validated on an animal model”
A responsibility gene, the SOD1 gene: the function of this gene is to provide instructions for the manufacture of the enzyme superoxide dismutase, which breaks down superoxide radicals, free radicals derived from oxygen, byproducts of processes normal cellular. Previous research has suggested that mutations in the SOD1 gene can lead to ineffective removal of these superoxide radicals or create other toxicities that cause the death of motor neurons, resulting in the development of ALS.

Silencing the guilty gene: the new approach is to inject an artificial RNA molecule capable of silencing or disabling the responsible gene. This molecule is delivered to cells via a harmless adeno-associated virus. Here, injections in 2 sites of the spinal cord of adult mice expressing a mutation of SOD1 causing ALS, either just before the onset of the disease, or at the onset of the first symptoms, allow almost complete protection. complete motor neurons, junctions between neurons and muscle fibers. In adult mice already showing ALS-like symptoms, the injection blocked the progression of the disease and the degeneration of the motor neurons. No negative side effects were seen in mice.

This is the prospect of an effective therapy, “the most powerful ever validated in murine models of ALS linked to the mutated SOD1 gene”, concludes the main author, Dr. Martin Marsala, professor in the Department of Anesthesiology of the UC San Diego School of Medicine. This new mode of delivery of gene silencing therapy may be effective in treating other inherited forms of ALS or other spinal neurodegenerative disorders that require gene therapy by spinal administration.

Finally, the team also tested the injection approach in adult pigs, whose dimensions of the spinal cord are similar to those of humans, to validate the safety and efficacy of the treatment.

Researchers confirm that the procedure can be performed reliably and without surgical complications. The next steps should validate safety and specify the optimal dosage for humans.

GLAUCOME: Treat it with a single injection of gene therapy?

This research team from Bristol Medical School presents here a new therapeutic option to treat glaucoma, one of the main causes of blindness in the world: it is a gene therapy, administered by injection and which targets the gene responsible for eye pressure. Work presented in the journal Molecular Therapy that opens up a whole new path, full of hope.

Glaucoma affects more than 64 million people worldwide and is one of the leading causes of irreversible blindness, especially in people over the age of 60. The condition is caused by the accumulation of fluid in the front part of the eye, which increases the pressure inside the eye and gradually damages the optic nerve. Current treatments include eye drops, laser or surgery, treatments that have limits and cause side effects. Lead author Dr. Colin Chu explains that there is currently no cure for glaucoma, which can lead to vision loss if the disease is not diagnosed and treated early enough.

Treat glaucoma with a single injection using gene therapy

A first proof of concept: the researchers bring here in vitro and in vivo a first proof of concept of therapy, on human tissues and in mice “models” of glaucoma. The therapy targets a part of the eye called the ciliary body (see histological section on visual 2), which produces the fluid that maintains pressure in the eye. Using the gene editing technology called CRISPR, researchers inactivate a gene called Aquaporin 1 in the ciliary body, which has reduced eye pressure.

1 injection would be enough: glaucoma could be successfully treated with a single injection using gene therapy, which would improve the treatment options, effectiveness and quality of life of many patients. “We hope to move quickly towards clinical trials. If they are successful, then we would have long-term treatment for glaucoma with a single eye injection, which would improve the quality of life for many patients while saving health care resources. “

Enzymes, biocatalysts

This week we will talk about enzymes, those molecules that participate in almost the majority of the reactions that occur in any living cell. Despite having repeated the word enzyme in much of the post written so far, something that shows its great importance, we have never focused on talking specifically about them.
Today we will discuss, in more detail, what they are about, how they are classified and what they are used for… KEEP READING!
What are enzymes?
Enzymes are biocatalysts, that is, they are the catalysts of biological reactions. Considering that a catalyst is a substance that accelerates the course of a chemical reaction, a biocatalyst or enzyme is a substance that accelerates a biological reaction, which, without its presence, could take years to complete.

Therefore, the role of enzymes is the catalysis or acceleration of biological reactions, which occur in living beings. An example? Degrade the proteins in the meat we eat to absorb all its nutrients. This biological reaction would be carried out by a specific type of enzymes, present in our gastrointestinal tract: proteases.

In addition to accelerating the speed of a certain reaction, enzymes have another characteristic characteristic of any catalyst, whether biological or not, and that is that they are not consumed during the reaction. That is, the enzyme acts, and after conducting and accelerating one reaction it can re-catalyze another.

What enzymes do have that non-biological catalysts do have are characteristics such as high specificity, since each type of enzyme acts on a single reaction; that they always act at the temperature of the living being in which they are; and that they have a very high activity, managing to increase the reaction speed in more than a million times.

Why does an enzyme speed up a biological reaction?
What the enzyme does is lower the activation energy that is needed for such a reaction to start. And here I will tell you the typical simile that appears in school textbooks: if you want to throw an object, which is on the ground, for the sale, you first have to force yourself to lift the object to the edge of the sale, ¿ true?

That would be the activation energy. Once that energy is exceeded, the reaction proceeds, or the object falls from the window, quickly. If the more expensive stage is accelerated, the reaction generally occurs more quickly. That is the mission of any enzyme.

How do enzymes work?
Enzymes consist of a region called the active center, the part of the enzyme to which the substrate, the molecule on which the reaction will take place, binds, specifically and exclusively.

The formation of the enzyme-substrate complex creates an environment that promotes biological reaction, if we continue with the example of proteins, protein degradation. Once the protein has been broken down into smaller fragments, these leave the enzyme and it remains intact, being able to act again, breaking down another protein.

What determines that an enzyme only has specificity for a specific substrate and reaction?
The specificity between the enzyme and the substrate can be:

Absolute: If the enzyme only acts on a substrate.
Group: The enzyme works on a certain group of molecules.
Class: The enzyme recognizes and acts depending on a specific area of ​​the substrate, and therefore does not depend on the type of molecule itself.
The substrate may fit into the active center of the enzyme like a key in your lock, it may have to change its shape to bind and form the enzyme-substrate complex, or both parts have to change their conformation. In both three cases, the enzyme-substrate interaction is carried out through specific links between both parties.

And watch out, because there are 3 factors that affect enzyme activity: temperature, pH and inhibitors. Normally, increasing the temperature increases the mobility of the molecules and therefore it is easier for the substrate and enzyme to meet and the reaction to take place. However, if we exceed a certain temperature, the enzyme breaks down and becomes unusable. Something similar happens with pH, ​​since outside of limit values, enzymes do not work properly either.

And finally the inhibitors, substances that prevent or diminish the action of an enzyme. Why? Because having a very similar shape to the substrate, they bind to the enzyme, blocking its active center and preventing the entry of the true substrate and therefore, the reaction.

How are enzymes classified?
Enzymes are classified into six main classes, according to the general type of reaction in which they participate:

Oxidoreductases: Accelerate or catalyze oxidation and reduction reactions. An example would be oxidases and dehydrogenases.
Transferase: They are dedicated to transfer groups or radicals between different molecules, such as hexokinase.
Hydrolases: Break chemical bonds by adding a molecule of water. A clear example would be lysozyme.
Liases: They separate groups without the intervention of water (without hydrolysis), originate double bonds or add CO2, such as rubisco.
Isomerases: They perform conversions within the same molecule, such as triosaphosphate isomerase.
Ligasas: They catalyze the union of molecules or groups thanks to ATP, such as DNA-ligase.
Within each class there are groups, subgroups and series, so each enzyme is assigned a 4-digit number that identifies it. And I don’t know if you have noticed, but a large part of the enzymes end in -asa, a trick that can be useful to identify them. For example: the enzyme that breaks down lactose is called lactase and it is the enzyme that lactose intolerant does not possess. Or the protein-degrading enzyme, protease.

Although at the moment only about 3000 different enzymes have been described, it is estimated that up to 10,000 could exist in nature.

What are enzymes used for in our day to day?
They are part of products such as detergents, in which enzymes such as lipases or proteases are added to break down the food residues that form stains on our clothes. In addition, they are used in manufacturing processes such as cheese, in which renin is added to curdle milk. They are part of diagnostic kits in clinical tests, such as peroxidase. Or they are used for the synthesis of antibiotics among many other applications.

More related information?
Zymogens or proenzymes: Enzymes or ions that have the function of activating an enzyme.

Isoenzymes: They are different forms of the same enzyme that catalyze the same reaction but can be present at different stages of life or in different organs and tissues.

Enzymes can be classified into two types according to their composition:

If they are strictly proteinic.
Holoenzymes: they have a protein part and a non-protein part called a cofactor. These cofactors can be inorganic (ions) or organic, also called coenzymes such as ATP or coenzyme A.