Could an Intranasal Spray Ease Neuroinflammation and Age-Related Brain Fog?
Intranasal administration of neural stem cell-derived EVs reduced neuroinflammation and improved memory in aged mice.
Results from a preclinical study by Texas A&M University researchers found that just two doses of a nasal spray reduced multiple markers of neuroinflammation and improved memory performance in aged mice. The research, published in the Journal of Extracellular Vesicles, suggests that the inflammation responsible for brain aging and brain fog might actually be reversible.
Brain fog and neuroinflammation: understanding the link
Brain fog refers to a collection of non-specific cognitive symptoms: slowed thinking, difficulty concentrating, memory issues, and overall mental fatigue.
Once dismissed as an inevitable part of aging, brain fog is now increasingly reported by young adults, menopausal women, and long COVID sufferers. It has become a significant public health concern.
Symptoms of brain fog are thought to reflect underlying disruptions in normal brain function. One of the proposed contributors to these changes is neuroinflammation—a chronic, low-grade inflammatory state in the brain. As symptoms of brain fog progress from a subtle reminder of cognitive inefficiency to a significant disruptor of daily life, it can impact safety, social integration, and emotional well-being, highlighting the need for effective intervention.
A research team at Texas A&M aims to provide this, and they started by testing whether a nasal spray could reduce neuroinflammation and improve memory.
Extracellular vesicles as a therapeutic approach to neuroinflammation
In recent years, extracellular vesicles (EVs) have garnered interest as a therapeutic delivery system across many indications, including neuroinflammation.
EVs from human induced pluripotent stem cell-derived neural stem cells (hiPSC-NSC-EVs) are enriched in functional proteins and nucleic acids, such as microRNA (miRNA), that can induce therapeutic effects. Dr. Madhu Leelavathi Narayana, senior research scientist at Texas A&M University, explained: “MicroRNAs act like master regulators; they help modulate and regulate many gene and signaling pathways in the brain.”
EVs are particularly attractive for neurological conditions for three main reasons:
- Suitability for intranasal delivery
- Reported ability to access the central nervous system
- Containment of intrinsic components with both anti-inflammatory and neuroprotective effects
“The mode of delivery is one of the most exciting aspects of our approach. Intranasal delivery allows us to reach, and treat, the brain directly without invasive procedures.” — Dr. Maheedhar Kodali, senior research scientist at Texas A&M University.
In this study, led by Dr. Ashok Shetty, the team investigated whether these qualities could reduce age-related neuroinflammation and improve cognitive function in mice.
The treatment group showed better memory function
The researchers tested intranasal delivery of hiPSC-NSC-EVs in 18-month-old mice; this age equates approximately to a 60-year-old human. The mice received two doses of the treatment, administered intranasally, two weeks apart, while an age-matched group received a control treatment.
One month after the final dose, animals underwent neurobehavioral tests to assess cognitive function. Tests included a novel object recognition test (NORT), which assessed their ability to distinguish between familiar and new objects, and an object location test (OLT), which assessed their ability to recognize changes in their environment.
Mice treated with hiPSC-NSC-EVs preferred to explore novel objects in the NORT, whereas the control group showed no preference. Additionally, the treatment group showed a preference for objects in new locations within the OLT, while the control group preferred objects in familiar places.
The preference for novelty was consistent among male and female mice in the treatment group and suggests improved performance of memory-based tasks with treatment.
EV therapy was delivered to the brain
The researchers recruited further subgroups for biodistribution studies. Immunofluorescence microscopy confirmed permeation across multiple brain regions, including uptake by microglia and neurons six hours post-administration. These biodistribution tests were crucial to evidence that EVs reached brain tissue.
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The biology behind the observed cognitive improvement
Following cognitive assessment, the cohorts were grouped for brain tissue analysis. One subgroup underwent immunohistochemical staining, while the other underwent biochemical and molecular biology studies. The researchers investigated key signaling pathways and markers implicated in inflammation in the hippocampus—the brain’s memory consolidation center (Table 1).
Table 1: Outcomes measured within the study and their relevance to neuroinflammation.
| Outcome measured | Relevance to neuroinflammation |
| Astrocyte hypertrophy | The enlargement of astrocytes, housekeeping cells within the brain that maintain homeostasis, is a hallmark of neuroinflammation. |
| Microglial clustering | The aggregation of microglia, the primary immune cells within the central nervous system, represents a transition from a surveying role to activation, associated with brain injury and toxic protein accumulation. |
| Oxidative stress markers | Assessments included nuclear factor erythroid 2-related factor, a transcription protein that regulates antioxidant response following oxidative stress. |
| Mitochondrial respiratory chain genes | Genes encoding proteins relevant to mitochondrial respiration, such as Ndufs7, were assessed. Upregulation of these genes is associated with oxidative stress responses. |
| Inflammasome genes and respective markers of activation | Researchers assessed nucleotide-binding domain leucine-rich repeat (NLR) family pyrin domain-containing 3 (NLPR3), a sensory component of an inflammasome complex. It is activated by toxic proteins, leading to activation of the inflammatory pathway and cell death. |
| Markers of cyclic GMP-AMP synthase (cGAS) and the stimulator of interferon genes (STING) pathway activation | In the cGAS-STING pathway, cGAS acts as a sensor within eukaryotic cells, detecting foreign or misplaced double-stranded DNA. Upon detection of foreign or misplaced double-stranded DNA, it activates STING, resulting in sustained immune inflammation. |
Significant reductions in markers of neuroinflammation were observed within the treatment group. Astrocyte hypertrophy and microglial clusters were reduced in both male and female mice in the treatment group.
Enhanced mitochondrial respiratory gene expression, reductions in markers of oxidative stress, and restrained activation of both the NLRP3 inflammasome cascade and the cGAS-STING pathway were also observed across both males and females in the treatment group, with some sex-dependent variation.
Shetty noted: “It’s universal. Treatment outcomes were consistent and similar across both sexes.”
How exactly do hiPSC-NSC-EVs suppress inflammatory pathways?
To understand how the treatment suppressed neuroinflammation, the team assessed the roles of naturally occurring miRNAs within the EVs. Both miR-30e-3p and miR-181a-5p are suggested to inhibit NLRP3 and STING, respectively.
Through generating inflammation in cell models and treating lines with normal, control, and knockdown EVs—ones with reduced levels of the miRNAs—the team assessed the individual impact of each miRNA on end-point inflammatory markers.
They found that depleted cells had higher levels of inflammatory cytokines, with miRNA-specific results suggesting that miR-30e-3p suppresses the NLRP3 inflammasome, while miR-181a-5p suppresses STING pathways.
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Transcriptomic changes: the mechanistic puzzle piece
With the understanding that EV treatment reduced inflammation and improved cognition, the team dug deeper, aiming to elucidate what was happening at the genetic level. Using single-cell RNA sequencing, they measured gene expression within microglia.
Shetty and his team found that EV treatment caused transcriptional changes, including downregulation of over 2000 genes and upregulation of over 800 genes. Among these, mitochondria-related genes were upregulated, while genes related to inflammation and stress were downregulated.
These findings suggest a shift toward a less inflammatory transcriptional profile in microglia following treatment with hiPSC-NSC-EVs.
Could an intranasal spray combat neuroinflammation and brain fog?
The findings provide converging behavioral, biological, mechanistic, and transcriptomic evidence that intranasal hiPSC-NSC-EVs can reduce neuroinflammation, and the team has now filed a patent application for the therapy.
“Brain age-related diseases like dementia are a major health concern worldwide. What we’re showing is brain aging can be reversed, to help people stay mentally sharp, socially engaged, and free from age-related decline,” said Shetty. “As we develop and scale this therapy, a simple, two-dose nasal spray could one day replace invasive, risky procedures or maybe even months of medication.”
However, as this is a preclinical study, it remains uncertain whether this approach will translate into meaningful outcomes in humans. Key questions remain: How would differences in intranasal cavity anatomy influence therapy delivery? Would these results be replicated in the more diverse context of the human brain? And will improvements in basic functions, such as spatial learning, translate into meaningful relief for people living with the consequences of an aging brain, including brain fog?
Despite the questions that remain, Shetty and the team feel positive about this therapy's potential: “Our approach redefines what it means to grow old. We’re aiming for successful brain aging: keeping people engaged, alert, and connected. Not just living longer, but living smarter and healthier.”
This article is a rework of a press release issued by Texas A&M University. Material has been edited for length and content.
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