To ensure that the drops were naturally inhaled into the nasal cavity, the opposite naris and mouth of the mice were kept closed during the administration. == Determination of Blood Glucose and Plasma Insulin Levels == Blood ITE samples were collected at 0 and 30min after intranasal administration of ITE exendin-4. anti-apoptotic proteins and decreased the expression of Caspase-3. The anti-apoptotic effect was mediated by the cAMP/PKA and PI3K/Akt pathway. These findings provided evidence that exendin-4 intranasal administration exerted a neuroprotective effect mediated by an anti-apoptotic mechanism in MCAO mice and protected neurons against ischemic injury through the GLP-1R pathway in the brain. Intranasal delivery of exendin-4 might be a promising strategy for the treatment of ischemic stroke. == Electronic supplementary material == The online version of this article (doi: 10. 1208/s12248-015-9854-1) contains supplementary material, which is available to authorized users. KEY WORDS: cerebral ischemia, exendin-4, intranasal delivery, neuroprotection == INTRODUCTION == Stroke is the second leading ITE cause of death worldwide in people aged 60 years or older (1). In addition , stroke is a leading cause of long-term severe disability (2). About 87% of all strokes are represented by ischemic strokes, when the blood flow to the brain is blocked (2). So far, the only drug used for the treatment of acute ischemic stroke approved by the US Food and Drug Administration (FDA) is tissue plasminogen activator (tPA) (3), which is intravenously administered to dissolve blood clots and restore blood flow. However , this thrombolytic therapy has a limited time window for treatment, and it is associated with risks of intracerebral hemorrhage particularly in patients having large-volume lesions (4, 5). Glucagon-like peptide-1 (GLP-1) is a gastrointestinal hormone which plays important roles in blood glucose control and is also considered as a neuropeptide synthesized by ITE neuronal cells. Glucagon-like peptide-1 receptor (GLP-1R) was found to be widely expressed in the brain (6), and its Mouse monoclonal to GFP activation protects against neurological disease (7). Exendin-4 is a long-lasting GLP-1R agonist which is widely used for the treatment of type 2 diabetes. The prolonged duration of its action and high apparentin vivopotency make exendin-4 more suitable as a potential pharmacological candidate. Besides its anti-diabetic effects, previous studies have shown that exendin-4 mediated neuroprotection in animal models of stroke (813). Intracerebroventricular injection of exendin-4 was found to exert neuroprotective effect against ischemic stroke in rats with middle cerebral artery occlusion (MCAO) surgery (8). Repeated administration of exendin-4 for 7 days was reported to reduce the infarct volume caused by MCAO in rats (10). Intravenous administration of exendin-4 provided neuroprotection against ischemic injury in mice at 1 h after MCAO, but the effect was lost at 3 h after MCAO (12). Moreover, in both young healthy and aged diabetic/obese mice, exendin-4 showed a neuroprotection against stroke induced by MCAO (9). Therefore , exendin-4 is considered to be a promising strategy for the treatment of cerebral ischemia. However , the blood-brain barrier blocks most small molecules and nearly all large molecules from reaching the diseased brain; thus, systemic delivery of therapeutic peptides are often found to be ineffective (14, 15). Peptidic drugs need to be administered at large doses to achieve therapeutic levels in the brain, which would increase the systemic adverse effects. Although peptidic drugs can be directly injected into the brain via intracerebroventricular administration, this invasive technique is not suitable for clinical use (8, ITE 16, 17). Hence, a noninvasive approach to bypass the blood-brain barrier to target the brain should be worthwhile. Intranasal administration is more convenient to the patient, and it alleviates the pain and discomfort associated with injections (18). In addition , this route has the potential to overcome the blood-brain barrier and reduce the side effects caused by systemic injection. Thus, this delivery system represents a novel alternative for the treatment of neurologic diseases (19, 20). Moreover, intranasal administration has the advantage of avoiding the gastrointestinal and hepatic metabolism (21, 22). The nasal cavity has a large surface area and nasal mucosa is highly vascularized; thus, the concentrations of neuroprotective peptides in the brain after intranasal administration are often higher than those observed by systemic injection (23). Furthermore, intranasal administration facilitates self-medication, thereby improving patient.
To ensure that the drops were naturally inhaled into the nasal cavity, the opposite naris and mouth of the mice were kept closed during the administration