Intranasal administration of interferon beta bypasses the blood–brain barrier to target the central nervous system and cervical lymph nodes: a non-invasive treatment strategy for multiple sclerosis

Can nasal drug delivery bypass the blood-brain barrier?: questioning the direct transport theory

The connection between the nasal cavity and the CNS by the olfactory neurones has been investigated extensively during the last decades with regard to its feasibility to serve as a direct drug transport route to the CSF and brain. This drug transport route has gained much interest as it may circumvent the blood-brain barrier (BBB), which prevents some drugs from entering the brain. Approximately 100 published papers mainly reporting animal experiments were reviewed to evaluate whether the experimental design used and the results generated provided adequate pharmacokinetic information to assess whether the investigated drug was transported directly from the olfactory area to the CNS. In the analysis the large anatomical differences between the olfactory areas of animals and humans and the experimental conditions used were evaluated. The aim of this paper was to establish the actual evidence for the feasibility of this direct transport route in humans. Twelve papers presented a sound experimental design to study direct nose to CNS transport of drugs based on the authors' criteria. Of these, only two studies in rats were able to provide results that can be seen as an indication for direct transport from the nose to the CNS. No pharmacokinetic evidence could be found to support a claim that nasal administration of drugs in humans will result in an enhanced delivery to their target sites in the brain compared with intravenous administration of the same drug under similar dosage conditions.

Intranasal delivery: physicochemical and therapeutic aspects

Interest in intranasal (IN) administration as a non-invasive route for drug delivery continues to grow rapidly. The nasal mucosa offers numerous benefits as a target issue for drug delivery, such as a large surface area for delivery, rapid drug onset, potential for central nervous system delivery, and no first-pass metabolism. A wide variety of therapeutic compounds can be delivered IN, including relatively large molecules such as peptides and proteins, particularly in the presence of permeation enhancers. The current review provides an in-depth discussion of therapeutic aspects of IN delivery including consideration of the intended indication, regimen, and patient population, as well as physicochemical properties of the drug itself. Case examples are provided to illustrate the utility of IN dosing. It is anticipated that the present review will prove useful for formulation scientists considering IN delivery as a delivery route.

Janus faces of microglia in multiple sclerosis

Multiple sclerosis (MS) is the most common cause of neurological disability in young adults. The disease is characterized by inflammatory reactions, demyelination and axonal loss in the brain, spinal cord and optic nerves. Microglia seem to play an important role in the inflammatory processes in MS, since they are found in actively demyelinating lesions. Their role in the differentiation of T cells could led to the expansion of inflammation and tissue destruction. However, microglia are also involved in the termination of an inflammatory response and produce protective factors. To be able to therapeutically manipulate microglia, their exact function in the onset and development of MS needs to be clarified. This review provides an overview of the functions of the most important microglia-associated molecules in MS, being CD40, B7-1 and B7-2, interferon-gamma, tumor necrosis factor-alpha, chemokines, prostanoids, and nitric oxide.

The fibrin-derived gamma377-395 peptide inhibits microglia activation and suppresses relapsing paralysis in central nervous system autoimmune disease

Perivascular microglia activation is a hallmark of inflammatory demyelination in multiple sclerosis (MS), but the mechanisms underlying microglia activation and specific strategies to attenuate their activation remain elusive. Here, we identify fibrinogen as a novel regulator of microglia activation and show that targeting of the interaction of fibrinogen with the microglia integrin receptor Mac-1 (α_Mβ₂, CD11b/CD18) is sufficient to suppress experimental autoimmune encephalomyelitis in mice that retain full coagulation function. We show that fibrinogen, which is deposited perivascularly in MS plaques, signals through Mac-1 and induces the differentiation of microglia to phagocytes via activation of Akt and Rho. Genetic disruption of fibrinogen–Mac-1 interaction in fibrinogen-γ^390-396A knock-in mice or pharmacologically impeding fibrinogen–Mac-1 interaction through intranasal delivery of a fibrinogen-derived inhibitory peptide (γ^377-395) attenuates microglia activation and suppresses relapsing paralysis. Because blocking fibrinogen–Mac-1 interactions affects the proinflammatory but not the procoagulant properties of fibrinogen, targeting the γ^377-395 fibrinogen epitope could represent a potential therapeutic strategy for MS and other neuroinflammatory diseases associated with blood-brain barrier disruption and microglia activation.

Intranasal insulin improves memory in humans: superiority of insulin aspart

There is compelling evidence that intranasal administration of regular human insulin (RH-I) improves memory in humans. Owing to the reduced tendency of its molecules to form hexamers, the rapid-acting insulin analog insulin aspart (ASP-I) is more rapidly absorbed than RH-I after subcutaneous administration. Since after intranasal insulin administration, ASP-I may also be expected to access the brain, we examined whether intranasal ASP-I has stronger beneficial effects on declarative memory than RH-I in humans. Acute (40 IU) and long-term (4 x 40 IU/day over 8 weeks) effects of intranasally administered ASP-I, RH-I, and placebo on declarative memory (word lists) were assessed in 36 healthy men in a between-subject design. Plasma insulin and glucose levels were not affected. After 8 weeks of treatment, however, word list recall was improved compared to placebo in both the ASP-I (p<0.01) and the RH-I groups (p<0.05). ASP-I-treated subjects performed even better than those of the RH-I-treated group (p<0.05). Our results indicate that insulin-induced memory improvement can be enhanced by using ASP-I. This finding may be especially relevant for a potential clinical administration of intranasal insulin in the treatment of memory disorders like Alzheimer's disease.

Advances in nasal drug delivery through tight junction technology

New approaches for enhancing intranasal drug delivery based on recent discoveries on the molecular biology of tight junctions (TJ) are significantly improving the bioavailability of 'non-Lipinsky' small molecules, and peptide, protein and oligonucleotide drugs. As knowledge of the structure and function of the TJ has developed, so has the ability to identify mechanism-based TJ modulators using high-throughput molecular biology-based screening methods. The present review focuses on recent developments on the TJ protein complex as a lipid raft-like membrane microdomain, the emerging role of unique endocytic pathways in regulating TJ dynamics, and the utility of techniques such as RNA interference and phage display to study TJ components and identify novel peptides and related molecules that can modulate their function. Experimental and statistical methodologies used for the identification of new classes of TJ modulators are described, which are capable of reversibly opening TJ barriers with broad potential to significantly improve intranasal and, eventually, oral drug delivery. The development of an advanced intranasal formulation for the obesity therapeutic PYY(3-36), the endogenous Y2 receptor agonist is also reviewed.

Strategies for intranasal delivery of therapeutics for the prevention and treatment of neuroAIDS

Intranasal drug administration is a noninvasive method of bypassing the blood-brain barrier (BBB) to deliver neurotrophins and other therapeutic agents to the brain and spinal cord. This method allows drugs that do not cross the BBB to be delivered to the central nervous system (CNS) and eliminates the need for systemic delivery, thereby reducing unwanted systemic side effects. Delivery from the nose to the CNS occurs within minutes along both the olfactory and trigeminal neural pathways. Intranasal delivery occurs by an extracellular route and does not require that drugs bind to any receptor or undergo axonal transport. Intranasal delivery also targets the nasal associated lymphatic tissues (NALT) and deep cervical lymph nodes. In addition, intranasally administered therapeutics are observed at high levels in the blood vessel walls and perivascular spaces of the cerebrovasculature. Using this intranasal method in animal models, researchers have successfully reduced stroke damage, reversed Alzheimer's neurodegeneration, reduced anxiety, improved memory, stimulated cerebral neurogenesis, and treated brain tumors. In humans, intranasal insulin has been shown to improve memory in normal adults and patients with Alzheimer's disease. Intranasal delivery strategies that can be employed to treat and prevent NeuroAIDS include: (1) target antiretrovirals to reach HIV that harbors in the CNS; (2) target therapeutics to protect neurons in the CNS; (3) modulate the neuroimmune function of moncyte/macrophages by targeting the lymphatics, perivascular spaces of the cerebrovasculature, and the CNS; and (4) improve memory and cognitive function by targeting therapeutics to the CNS.

Effects of interferon-beta on oligodendroglial cells

The effect of interferon-beta (IFN-beta) for the treatment of multiple sclerosis (MS) is thought to be mediated by the modulation of immune cells. In addition, it has been shown that glial cells may be influenced by IFN-beta and a role during remyelination has been suggested. However, the mechanism is not yet clear and there are conflicting data. We have therefore systematically investigated proliferation, differentiation, toxicity, and cytoprotection of IFN-beta on oligodendroglia, both as a direct effect and mediated indirectly via other glial cells. Differentiation of oligodendrocyte progenitor cells (OPC) was significantly (p<0.01) inhibited by IFN-beta only when cultured in the presence with astrocytes and microglia. Proliferation was not changed, neither was IFN-beta toxic. There was no cytoprotective effect of IFN-beta on oligodendroglia injury induced by H2O2, NO, complement, or glutamate. Similarly, there was no cytoprotective effect mediated via treatment of astrocytes with IFN-beta. These data demonstrate that IFN-beta is neither toxic nor cytoprotective for oligodendrocytes. In summary, the only effect of IFN-beta was the inhibition of differentiation of OPC mediated indirectly via other glial cells. In vivo experiments will show how this effect may influence remyelination.

Therapeutic role of beta-interferons in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS). In the last 12 years, there has been a proliferation of studies elucidating the immune mechanisms that mediate tissue damage in MS. Interferons (IFNs) have an important role in regulating innate and adaptive immune responses. They decrease pro-inflammatory responses such as the autoimmunity in MS, but other autoimmune responses such as systemic lupus erythematosus (SLE) may be exacerbated. This review offers a general overview of the biological properties of IFNs, effects on immune cells, and clinical effectiveness in MS treatment. IFN signaling is complex, from receptor binding events to the generation of effector mechanisms that dampen inflammation. Immune cell function is altered in MS. IFN treatment of MS patients ameliorates immune dysfunction, but not completely. The incomplete resolution of immune dysfunction by IFNs partly explains their significant, but modest therapeutic effects. This observation also suggests that there are immune mechanisms in MS that are resistant to IFN therapy. In MS, abnormalities may exist at several points along the IFN signaling pathway, including molecular defects in the IFN second messenger system. Currently, several studies are ongoing evaluating ways of potentiating IFN effects. IFNs were the first agents to show clinical efficacy in treatment of MS. More than a decade of experience with IFNs has showed continued clinical efficacy over time. In the near future, IFNs will continue to play a major role in MS.

Pharmacokinetics, toxicity of nasal cilia and immunomodulating effects in Sprague-Dawley rats following intranasal delivery of thymopentin with or without absorption enhancers

Thymopentin (TP 5), a synthetic pentapeptide, has been used in clinic as a modulator for immnuodeficiencies through intramuscular administration. The objectives of this study was to investigate the pharmacokinetics using normal rats and toxicity of nasal cilia as well as immunomodulating effects using immunosuppression rats after intranasal delivery of thymopentin with or without an absorption enhancer. The absorption extent of fluorescein isothiocyanate (FITC) labeled TP 5 via nasal delivery at a single dose is significantly improved by incorporating sodium deoxycholate, Brij 35 and chitosan, respectively. FITC-TP 5 can also be absorbed to such an extent ranging from 15 to 28% after intranasal administration of FITC-TP 5 alone, FITC-TP 5 with sodium caprylate, or with bacitracin, respectively. After seven consecutive days multiple dosing, TP 5 formulation with sodium deoxycholate or Brij 35 caused apparently injury to nasal cilia, indicating these two enhancers would not be appropriate for nasal delivery. Results from superoxide dismutase activity, maleic dialdehyde, T-lymphocyte subsets (CD3+, CD4+, CD8+ and CD4+/CD8+ ratio) analyses suggest that all the selected enhancers improve the modulating effects of TP 5 in the immunosuppression rats. On an overall evaluation, intranasal TP 5 alone, TP 5 with chitosan, or TP 5 with bacitracin formulation may be suitable for the future clinical application.

Induction and blockage of oligodendrogenesis by differently activated microglia in an animal model of multiple sclerosis

The role of activated microglia (MG) in demyelinating neurodegenerative diseases such as multiple sclerosis is controversial. Here we show that high, but not low, levels of IFN-gamma (a cytokine associated with inflammatory autoimmune diseases) conferred on rodent MG a phenotype that impeded oligodendrogenesis from adult neural stem/progenitor cells. IL-4 reversed the impediment, attenuated TNF-alpha production, and overcame blockage of IGF-I production caused by IFN-gamma. In rodents with acute or chronic EAE, injection of IL-4-activated MG into the cerebrospinal fluid resulted in increased oligodendrogenesis in the spinal cord and improved clinical symptoms. The newly formed oligodendrocytes were spatially associated with MG expressing MHC class II proteins and IGF-I. These results point to what we believe to be a novel role for MG in oligodendrogenesis from the endogenous stem cell pool.

Effects of intranasal insulin on cognition in memory-impaired older adults: Modulation by APOE genotype

Raising insulin acutely in the periphery and in brain improves verbal memory. Intranasal insulin administration, which raises insulin acutely in the CNS without raising plasma insulin levels, provides an opportunity to determine whether these effects are mediated by central insulin or peripheral processes. Based on prior research with intravenous insulin, we predicted that the treatment response would differ between subjects with (epsilon4+) and without (epsilon4-) the APOE-epsilon4 allele. On separate mornings, 26 memory-impaired subjects (13 with early Alzheimer's disease and 13 with amnestic mild cognitive impairment) and 35 normal controls each underwent three intranasal treatment conditions consisting of saline (placebo) or insulin (20 or 40 IU). Cognition was tested 15 min post-treatment, and blood was acquired at baseline and 45 min after treatment. Intranasal insulin treatment did not change plasma insulin or glucose levels. Insulin treatment facilitated recall on two measures of verbal memory in memory-impaired epsilon4- adults. These effects were stronger for memory-impaired epsilon4- subjects than for memory-impaired epsilon4+ subjects and normal adults. Unexpectedly, memory-impaired epsilon4+ subjects showed poorer recall following insulin administration on one test of memory. These findings suggest that intranasal insulin administration may have therapeutic benefit without the risk of peripheral hypoglycemia and provide further evidence for apolipoprotein E (APOE) related differences in insulin metabolism.

Factors of importance for a successful delivery system for proteins

Protein pharmaceuticals have matured into an important class of drugs, now comprising one in three novel drugs introduced on the market. However, significant gains are still to be made in reducing the costs of production, ensuring proper pharmacokinetics and efficacy, increasing patient compliance and convenience, and reducing side effects such as immunogenicity. This review summarises these issues and provides recent examples of methods to reduce costs, alter pharmacokinetics and increase patient compliance. It also discusses the increasing interest in understanding immunogenicity in order to prevent failure of the protein drug or serious life-threatening side effects due to autoimmunogenicity.

Rapid Screening of Blood-Brain Barrier Penetration of Drugs Using the Immobilized Artificial Membrane Phosphatidylcholine Column Chromatography

The chromatographic capacity factors (kIAM) of 23 structurally diverse drugs were measured by the immobilized artificial membrane (kIAM) phosphatidylcholine chromatography for the prediction of blood-brain barrier (BBB) penetration. The kIAM was determined using themobile phase consisting of acetonitrile:DPBS (20:80 v/v) and corrected for the molar volume of the solutes (kIAM/MWn). The correlation between kIAM/MWn and CNS penetration was highest when measured at pH 5.5 with the power function of n = 4. This in vitro predictionmethod was validated with 7 newly synthesized PDE-4 inhibitors. The relationship between in vivo plasma-to-brain concentration ratios and in vitro CNS penetration was excellent ( r= 0.959). The developed in vitro prediction method may be used as a rapid screening tool for BBB penetration of drugs with passive transport mechanism, with high success, low cost, and reproducibility.

Intranasal recombinant human erythropoietin protects rats against focal cerebral ischemia

Erythropoietin (EPO) is a hematopoietic growth factor with tissue-protective properties, and can protect animals from cerebral ischemic injury. However, the central nervous effects of EPO as a glycoprotein is limited by the potential complication resulted from its erythropoietic activity and the problem of the penetration through blood-brain barrier (BBB). To avoid these limitations, in this study we administered recombinant human EPO (rhEPO) intranasally (i.n.) to evaluate its neuroprotective effect in the rats with focal cerebral ischemia induced by middle cerebral artery occlusion (MCAO). We found that rhEPO i.n. at doses of 4.8, 12 and 24 U (administered 10 min after MCAO and 1h after reperfusion) reduced infarct volume, brain swelling and cell damage in the ischemic hemispheres, and improved behavioral dysfunction 24 h after cerebral ischemia. Intraperitoneal rhEPO (5000 U/kg) also showed the protective effect, but the heat-inactivated rhEPO did not show any effect. Thus, intranasal administration of relatively small doses of rhEPO protects rats from acute injury after focal cerebral ischemia, suggesting that intranasal rhEPO may be a more effective and safer administration route for treatments of ischemic or other brain diseases.

Immediate but not long-term intranasal administration of insulin raises blood pressure in human beings

Intranasal administration of insulin has been shown to influence neuroendocrine functions via an effect on central nervous mechanisms. Because insulin, in particular when infused into cerebral arteries, induces blood pressure (BP) elevation by an unknown mechanism, we investigated whether insulin exerts similar effects on BP after intranasal administration. To evaluate the immediate effects of insulin on BP, 20 IU of human insulin was intranasally administered every 10 minutes over a 2-hour period. Blood pressure, heart rate, and muscular sympathetic nervous activity (MSNA) were continuously monitored. For evaluating the effects of subchronic administration of insulin, changes during and after 8 weeks of treatment with 160 IU insulin/d on BP were monitored. Compared with placebo, the immediate nasal administration of insulin raised diastolic BP (12.21% +/- 5.10%; P < .05), mean arterial BP (10.81% +/- 4.32%; P < .04), and systolic BP (9.53% +/- 4.66%; P < .08), whereas MSNA and heart rate were unaffected. In contrast, prolonged intranasal insulin administration did not affect BP (P > .62 for all comparisons). The immediate increase in BP in the face of an unsuppressed MSNA after insulin suggests that intranasal insulin transiently changes the baroreflex set point. Thus, data suggest that intranasal insulin administration affects BP regulatory centers in the brain. However, the effect is not observed with prolonged administration of the hormone, suggesting the emergence of counterregulatory processes.

Intranasal oxytocin administration attenuates the ACTH stress response in monkeys

Social relationships protect against the development of stress-related psychiatric disorders, yet little is known about the neurobiology that regulates this phenomenon. Recent evidence suggests that oxytocin (OT), a neuropeptide involved in social bond formation, may play a role. This experiment investigated the effects of chronic intranasal OT administration on acute stress-induced hypothalamic-pituitary-adrenal (HPA) axis activation in adult female squirrel monkeys. Subjects were randomized to one of two experimental conditions. Monkeys were intranasally administered either 50 microg oxytocin (N = 6 monkeys) or 0 microg oxytocin (N = 6 monkeys)/300 microl saline once a day for eight consecutive days. Immediately after drug administration on the eighth day, all monkeys were exposed to acute social isolation. Blood samples for determinations of adrenocorticotropic hormone (ACTH) and cortisol concentrations were collected after 30 and 90 min of stress exposure. Consistent with an anti-stress effect, OT-treated monkeys exhibited lower ACTH concentrations compared to saline-treated monkeys after 90 min of social isolation (F(1,7) = 6.891; P = 0.034). No drug-related differences in cortisol levels were observed, indicating that OT does not directly attenuate the adrenal stress response. Intranasal peptide administration has been shown to penetrate the central nervous system, and research must determine whether intranasally delivered OT exerts its effect(s) at a pituitary and/or brain level. This primate model offers critical opportunities to improve our understanding of the anti-stress effects of OT and may lead to novel pharmacological treatments for stress-related psychiatric disorders.

Development of a novel high-concentration galantamine formulation suitable for intranasal delivery

The goal of the current study was to develop an intranasal (IN) formulation of the acetylcholinesterase inhibitor galantamine, an important therapeutic for treating Alzheimer's disease. To allow for delivering a therapeutically relevant dose, it was necessary to greatly enhance drug solubility. Various approaches were examined to this end, including adding co-solvents, cyclodextrins, and counterion exchange. Of these, the latter, for example, replacement of bromide ion with lactate or gluconate, resulted in a dramatic drug solubility increase, more than 12-fold. NMR confirmed the molecular structure of new drug salt forms. An in vitro epithelial tissue model was used to assess drug permeability and cellular toxicity. In vitro, galantamine lactate formulations performed as well as or better than their hydrobromide (HBr) counterparts with respect to drug permeation across the epithelial membrane with minimal toxicity. In vivo studies in rats compared pharmacokinetic (PK) profiles of different formulations. The in vivo studies confirmed that IN galantamine achieves systemic blood levels comparable to those of conventional oral administration. Both the in vitro and in vivo data support the feasibility of IN administration of this important drug.