The study demonstrated that intranasal administration of COG-201, an shRNA designed to silence the HTR2A gene, significantly reduced anxiety and improved memory in mice and rats. These findings suggest that COG-201 may become a promising therapeutic approach to simultaneously treat cognitive deficits and anxiety disorders, paving the way for new strategies in the fight against neurodegenerative diseases.
Neurological disorders, such as mild cognitive impairment (MCI) and chronic anxiety, are a major public health challenge, affecting millions of people worldwide.
Mild cognitive impairment is an intermediate stage between normal aging and dementia, characterized by mild but noticeable cognitive difficulties that do not seriously interfere with daily activities.
Studies indicate that the prevalence of mild cognitive impairment varies between 5% and 36.7%, depending on the diagnostic criteria used. In addition, approximately 21% of people with mild cognitive impairment also suffer from anxiety.
Given these numbers, it is estimated that between 1.5 and 2 million Americans may have mild cognitive impairment accompanied by an anxiety disorder. There is currently no medication that treats both cognitive impairment and anxiety in these individuals at the same time.
In view of this therapeutic gap, new approaches based on precision biotechnology, such as RNA interference (RNAi), are being explored as possible solutions.
RNA interference is a natural cellular process that can be used to "turn off" specific genes, preventing the production of proteins associated with diseases. One of the most promising forms of this technology is short hairpin RNA (shRNA), a small RNA sequence designed to bind to a target gene and prevent its expression.
In the current study, scientists from the University of California, USA, developed an shRNA to silence the HTR2A gene, responsible for encoding the serotonin 5-HT2A receptor. This receptor has been associated with both anxiety disorders and memory.
The short hairpin RNA was inserted into an AAV9 viral vector, a modified virus that serves as a carrier of the genetic material. The DNA inside the virus was designed to be activated only in neuronal cells, using a specific promoter called MeCP2.
This gene complex, called COG-201, was administered intranasally to mice and rats, resulting in a significant reduction in anxiety and improved performance in memory tests.
To further assess the effects of COG-201, the researchers analyzed the animals’ behavior and brain activity before and after treatment. The memory tests were conducted using a novel object recognition model, in which the animals explore an environment containing a familiar object and a novel object.
Short hairpin RNA (shRNA)
Normally, animals with good memories spend more time exploring the new object, while those with cognitive deficits tend not to differentiate between the two. The results showed that mice treated with COG-201 had a significant increase in the discrimination index, that is, they spent more time interacting with the new object, indicating an improvement in memory retention.
In contrast, the control group (which received only a vehicle without the active shRNA) presented a negative discrimination index, suggesting that the animals were unable to remember the familiar object or were under the influence of anxiety and stress.
In addition to the behavioral tests, experiments were performed with primary cortical neurons from mice in the laboratory. These neurons were treated with COG-201 and then analyzed for their electrical activity, a fundamental parameter for understanding how the brain works.
The technique used, called multielectrode array (MEA), measures the quantity and frequency of electrical impulses generated by neurons.
Multiple electrode arrays (MEAs). The image shows a diagram of MEAs (top row), a photograph of an MEA that more clearly depicts the culture dish situated above the electrode array (left of middle row), and a micrograph of neuronal clusters within the MEA. The bottom panel shows a higher magnification image of neurons. Image: Thomas B. Shea
The results showed that HTR2A gene expression was significantly reduced in the treated neurons, which led to a decrease in the spontaneous electrical activity of these cells.
Significant decreases were observed in several parameters, such as the number of electrical spikes, the average neuronal firing rate, and the neural synchrony index, indicating a reduction in the neuronal hyperactivity associated with anxiety disorders.
Interestingly, there was an increase in the number of network bursts, which may indicate a compensatory mechanism in the brain to balance neuronal activity and optimize communication between neurons.
Treatment of primary mouse cortical neurons with COG-201 leads to downregulation of the 5-HT2A receptor. Representative immunofluorescence images of mouse neurons after 10 days of treatment with empty viral particles (A–D) or COG-201 (E–H). Green fluorescence represents COG-201 expression (B and F), while red fluorescence is indicative of 5-HT2A receptor protein.
The combination of evidence obtained both in vivo (in living mice) and in vitro (in neuronal cultures) suggests that COG-201 has strong therapeutic potential to simultaneously treat anxiety and memory deficits.
The intranasal administration of this treatment represents a major advantage, as it is a non-invasive method, allowing the shRNA to directly reach the brain without the need for surgical procedures.
Furthermore, by modulating a specific gene related to anxiety and cognition, this approach avoids the systemic side effects common to traditional medications that affect multiple body systems.
If the results observed in animal models can be replicated in humans, COG-201 could pave the way for the development of new treatments for generalized anxiety disorder, post-traumatic stress disorder (PTSD), and cognitive deficits associated with aging and neurodegenerative diseases such as Alzheimer's.
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Treatment with shRNA to knockdown the 5-HT2A receptor improves memory in vivo and decreases excitability in primary cortical neurons
Troy T. Rohn, Dean Radin, Tracy Brandmeyer, Peter G. Seidler, Barry J. Linder, Tom Lytle, David Pyrce, John L. Mee, and Fabio Macciardi
Genomic Psychiatry
Abstract:
Short hairpin RNAs (shRNA), targeting knockdown of specific genes, hold enormous promise for precision-based therapeutics to treat numerous neurodegenerative disorders. We designed an AAV9-shRNA targeting the downregulation of the 5-HT2A receptor, and recently demonstrated that intranasal delivery of this shRNA (referred to as COG-201), decreased anxiety and enhanced memory in mice and rats. In the current study, we provide additional in vivo data supporting a role of COG-201 in enhancing memory and functional in vitro data, whereby knockdown of the 5-HT2A receptor in primary mouse cortical neurons led to a significant decrease in mRNA expression (p = 0.0007), protein expression p-value = 0.0002, and in spontaneous electrical activity as measured by multielectrode array. In this regard, we observed a significant decrease in the number of spikes (p-value = 0.002), the mean firing rate (p-value = 0.002), the number of bursts (p-value = 0.015), and a decrease in the synchrony index (p-value = 0.005). The decrease in mRNA and protein expression, along with reduced spontaneous electrical activity in primary mouse cortical neurons, corroborate our in vivo findings and underscore the efficacy of COG-201 in decreasing HTR2A gene expression. This convergence of in vitro and in vivo evidence solidifies the potential of COG-201 as a targeted therapeutic strategy. The ability of COG-201 to decrease anxiety and enhance memory in animal models suggests that similar benefits might be achievable in humans. This could lead to the development of new treatments for conditions like generalized anxiety disorder, post-traumatic stress disorder (PTSD), and cognitive impairments associated with aging or neurodegenerative diseases.
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