Neurodegenerative Diseases due to Neurotoxins passing through the Nose-to-Brain Pathway

Abstract

Three neurodegenerative disorders- Alzheimer’s dementia (ALZ), Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS)- share a common feature in their pathogenesis: evidence of mitochondrial dysfunction and reactive oxygen stress. Their pathologic classifications are based on the findings at autopsy based on patterns of protein aggregates in neurons and glial cells. This pathology supports the concept that neurotoxins are a major factor in the etiology of these disorders. There is value in exploring the similarities in the pathogenesis of ALS, Parkinson Disease and Alzheimer Dementia based on non-genetic etiologies. The nose to olfactory pathway feeds sensory input from the nasal cavity to the olfactory bulb and the entorhinal lobe. Another component of these pathways involves two branches of the trigeminal nerve with sensory input to the pons and midbrain. A key factor is their capacity to bypass the blood-brain barrier (BBB). The protection of the brain by the BBB diminishes with age and can be lost with damage from insults as with viral infections. The olfactory nerve is the only cranial nerve with direct exposure to the ambient environment and has a high rate of turnover of sensory receptors. The nasal cavity is being studied for drug delivery and can be used to deliver medications into the central nervous system (CNS. The nose-to-brain pathway may represent a critical avenue of exposure to oxidative neurotoxins. Neurotoxic mycotoxins are a major risk to humans. Neurotoxins may be amplified by the nose-to-brain pathway. The pathology shows similarities to prion disease. These neurotoxins are highly fat-soluble and tend to accumulate in mitochondria and synaptic vesicles. Neurotoxins in synaptic vesicles can migrate from neuron to neuron. There is evidence of chronic fungal infections in ALS patients that secret neurotoxic and immunotoxic mycotoxins leading to progressive immune suppression. The nose-to-olfactory pathway may amplify neurotoxins levels in the brain. If Parkinson Disease and ALZ are due to systemic poisonings, the source of neurotoxins may be episodic and lead to autoimmune disease.