J Alzheimers Dis. 2013;35(4):777-88.

Brain transit and ameliorative effects of intranasally delivered anti-amyloid-β oligomer antibody in 5XFAD mice.

Xiao C, Davis FJ, Chauhan BC, Viola KL, Lacor PN, Velasco PT, Klein WL, Chauhan NB.

Neuroscience Research, Jesse Brown VA Medical Center, Chicago, IL 60612, USA.

 

Abstract

Alzheimer’s disease (AD) is a global health crisis with limited treatment options. Despite major advances in neurotherapeutics, poor brain penetration due to the blood-brain barrier continues to pose a big challenge in overcoming the access of therapeutics to the central nervous system. In that regard, the non-invasive intranasal route of brain targeting is gaining considerable attention. The nasal mucosa offers a large surface area, rapid absorption, and avoidance of first-pass metabolism increasing drug bioavailability with less systemic side effects. Intranasal delivery is known to utilize olfactory, rostral migratory stream, and trigeminal routes to reach the brain. This investigation confirmed that intranasal delivery of oligomeric amyloid-ß antibody (anti-Aß antibody) utilized all three routes to enter the brain with a resident time of 96 hours post single bolus intranasal administration, and showed evidence of perikaryal and parenchymal uptake of anti-Aß antibody in 5XFAD mouse brain, confirming the intranasal route as a non-invasive and efficient way of delivering therapeutics to the brain. In addition, this study demonstrated that intranasal delivery of anti-Aß antibody lowered cerebral amyloid-ß antibody and improved spatial learning in 5XFAD mice.

 

Supplements:

Alzheimer’s disease (AD) is an age-associated neurodegenerative disease currently afflicting >5 million Americans, with the projected escalation to >16 million by 2050 if effective disease-modifying treatments are not discovered. Based on widely accepted concept of overproduction and deposition of ß-amyloid peptide (Aß) as a key seeding event in the pathogenesis of AD, removal of Aß by immunotherapeutic strategies continues to be one of the promising strategies in treating AD. Although partially successful, all immunization strategies explored thus far are posed with various limitations. Passive immunization using anti-Aß antibodies directly delivered to the brain via intracranial route have shown greater benefits than indirect access of anti-Aß antibodies derived from active or systemic passive immunization strategies. However, direct delivery of antibodies to the brain via an intracranial route is potentially limited due to its invasiveness. In that regard, intranasal (IN) route of direct drug delivery to the brain is increasingly gaining interest as a non-invasive and safe approach to target therapeutics directly to the brain. Although IN route has been utilized to deliver various growth factors or insulin and its mimetics, there are very few reports showing intranasal delivery of anti-Aß antibody in AD-models or in Alzheimer’s disease.

Fig 1_Submitted for World BioMed Front

Fig 1. Representative photographs showing positioning of an anesthetized mouse (A) to be injected intranasally with the antibody using a microliter pipette-tip targeted over one naris (B).

This is the first report showing the detailed anatomical brain distribution and uptake of intranasally delivered anti-Aß antibody utilizing these routes in 5XFAD Alzheimer’s transgenic mice. Conventionally, intranasally administered material is taken up by sensory neurons of Gruenberg ganglion and sepal organ projecting to the olfactory epithelium, by ventronasal organ projecting to the accessory olfactory bulb and by olfactory epithelium projecting to the granule cell layer and plexiform layers, eventually draining the IN-administered material into the accessory olfactory bulb (AOB), RMS, olfactory tract and trigeminal tract. While the IN-delivered material tracked into the RMS reaches the lateral and 3rd ventricle in the close vicinity of hippocampus, the material tracked into the olfactory tract from AOB and olfactory lobe delivers material into the midbrain, and the material trafficked along the trigeminal track delivers to pons and hind brain, reaching to the 4th ventricle, thus distributing IN-delivered material all throughout the brain.

Fig 2_Submitted for World BioMed Front


Fig 2. Schema showing major routes of entry utilized after intranasal delivery of therapeutics in mice. Intranasally administered material (Yellow deposits) is picked up by sensory neurons of Grueneberg ganglion, Septal Organ (Green arrows), Olfactory epithelium (Blue arrow), and Ventro-nasal organ (Red arrow). The sensory neurons of Grueneberg ganglion, Septal Organ (Green arrows) and Olfactory epithelium (Blue arrow)- all projecting to the granule cells of the olfactory lobe, eventually drain IN-administered material into the Rostral Migratory Stream (RMS) (Yellow Arrowheads) and olfactory track at the base of the mid-brain (Blue and red Arrows). The material tracked into the RMS reaches the lateral and 3rd ventricle in the close vicinity of hippocampus. The sensory neurons of Ventro-nasal organ (Red arrows) project to the “Accessory Olfactory Lobe (AOB), which further combine with the olfactory track at the base of the mid-brain. The material trafficked along the trigeminal nerve also combines with the olfactory track delivering to Pons and hind brain, reaching to the 4th ventricle.

Currently observed entry of HRP-labeled anti-Aß antibody right across the glomerular and plexiform layers of olfactory epithelium after 2h post IN administration of anti-Aß antibody is consistent with the known facts of being trafficked through the sensory neurons of Gruenberg ganglion and septal organ projecting to the olfactory epithelium, as well as directly taken up by olfactory epithelium in the nasal cavity. This transit was further observed to progress along the olfactory tract which appeared to have merged with the trigeminal path as evidenced by detection of HRP-anti-Aß antibody label at the base of the midbrain. The detection of HRP-anti-Aß antibody within the 4th ventricle provides additional confirmation of anti-Aß antibody being trafficked through the trigeminal route as well because it is the trigeminal path that conventionally projects IN-delivered material to the pons, hind brain and 4th ventricle. On the other hand, detection of HRP-anti-Aß antibody within the AOB by 6h post IN-administration confirms the trafficking of IN-delivered anti-Aß antibody gets picked up by the septal organ projecting to AOB, eventually draining into the olfactory path.

Fig 3_Submitted for World BioMed Front

Fig 3. Representative photomicrograph showing the uptake of intranasally injected antibody in the Accessory Olfactory Lobe (AOB) (Red arrowhead) and Rostral Migratory Stream (RMS) (Blue arrow) track.

Current investigation provided anatomical evidence of the involvement of olfactory, rostral migratory stream and trigeminal transit routes for IN delivered anti-Aß antibody to enter the brain parenchyma with a resident time of 96 hours post single bolus intranasal administration and showed an evidence of perikaryal and perisomal uptake in 5XFAD brain, confirming the intranasal route as a safe, non-invasive and efficient way of administering therapeutics to the brain. In addition, this study confirmed that intranasally administered anti-Aß antibody was able to neutralize brain parenchymal Aß preventing progressive accumulation of cerebral amyloid, resulting in the improvement of spatial acquisition learning-the hippocampal-based cognitive task.

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