Human nasal mucosal carboxypeptidase: activity, location, and release

Intranasal drug delivery: an efficient and non-invasive route for systemic administration: focus on opioids

Intranasal administration is a non-invasive route for drug delivery, which is widely used for the local treatment of rhinitis or nasal polyposis. Since drugs can be absorbed into the systemic circulation through the nasal mucosa, this route may also be used in a range of acute or chronic conditions requiring considerable systemic exposure. Indeed, it offers advantages such as ease of administration, rapid onset of action, and avoidance of first-pass metabolism, which consequently offers for example an interesting alternative to intravenous, subcutaneous, oral transmucosal, oral or rectal administration in the management of pain with opioids. Given these indisputable interests, fentanyl-containing formulations have been recently approved and marketed for the treatment of breakthrough cancer pain. This review will outline the relevant aspects of the therapeutic interest and limits of intranasal delivery of drugs, with a special focus on opioids, together with an in-depth discussion of the physiological characteristics of the nasal cavity as well as physicochemical properties (lipophilicity, molecular weight, ionisation) and pharmaceutical factors (absorption enhancers, devices for application) that should be considered for the development of nasal drugs.

Intranasal delivery--modification of drug metabolism and brain disposition

Intranasal route continues to be one of the main focuses of drug delivery research. Although it is generally perceived that the nasal route could avoid the first-pass metabolism in liver and gastrointestinal tract, the role of metabolic conversions in systemic and brain-targeted deliveries of the parent compounds and their metabolites should not be underestimated. In this commentary, metabolite formations after intranasal and other routes of administration are compared. Also, the disposition of metabolites in plasma and brain after nasal administrations of parent drugs, prodrugs and preformed metabolites will be discussed. The importance and implications of metabolism for future nasal drug development are highlighted.

High abundance of testosterone and salivary androgen-binding protein in the lateral nasal gland of male mice

To better understand androgen function in the mammalian nose, we have determined the levels of testosterone (T) in the olfactory mucosa (OM, which harbors the olfactory receptor neurons) and the lateral nasal gland (LNG, which is the largest anterior nasal gland) of C57BL/6 mice. The results indicated that, in adult male mice, T levels in the LNG were substantially higher than those in the OM and other non-reproductive or non-endocrine tissues examined, including liver, kidney, and brain. Furthermore, in the LNG, the high T levels were accompanied by high levels of salivary androgen-binding protein (sABP) and low microsomal T-hydroxylase activities. The high abundance of T and sABP in the LNG suggests not only that the LNG is a storage site for androgen, but also the possibility that unusually high T levels may occur in other organs that have abundant expression of sABP but low expression of steroid-metabolizing enzymes. Our findings suggest a critical need to determine androgen levels in various organs, as well as to establish the functional significance of an unusually high T level in the LNG, a gland known for its secretion of biologically active molecules, such as odorant binding proteins and immunoglobulin A, to the nasal cavity.

Anisylazoformylarginine: a superior assay substrate for carboxypeptidase B type enzymes

Anisylazoformylarginine (CH(3)OC(6)H(4)-N=N-CO-Arg-OH) is rapidly hydrolyzed at the acyl-arginine linkage by the zinc-enzyme porcine carboxypeptidase B. The catalytic reaction is readily monitored spectrophotometrically by disappearance of the intense absorption (349 nm, epsilon 19,100) of the azo chromophore, which chemically fragments after substrate cleavage.

Aminopeptidase activity in human nasal mucosa

BACKGROUND

Aminopeptidases activate bradykinin and degrade many inflammatory peptides.

OBJECTIVE

The objective of this study was to identify the types of aminopeptidase activities in human nasal mucosa.

METHODS

Human nasal mucosa was homogenized (n = 12), and cytoplasmic (S2) and membrane-rich (P2) fractions were obtained. Several aminopeptidase (Ap) activities were defined by (1) substrate specificity with leucine-enkephalin (leu-Ap) and alanine-nitroanilide (ala-Ap), (2) inhibitor studies with puromycin and bestatin, (3) enzyme activity histochemistry (zymography), (4) immunohistochemistry, and (5) gel electrophoresis. Human volunteers had methacholine, histamine, and allergen nasal provocations to determine the mechanisms controlling nasal aminopeptidase secretion in vivo.

RESULTS

P2 was the largest reservoir of puromycin-resistant aminopeptidase activity (630 pmol leu-enk/min/mg protein). S2 contained 32 pmol leu-enk/min/mg activity, with 80% representing puromycin-resistant activity and 20% puromycin-sensitive aminopeptidase (PS-Ap). Ala-Ap was detected in both P2 and S2 fractions and was localized by zymography to epithelial and gland cells. Anti-rat brain-soluble PS-Ap IgG detected immunoreactive material in epithelium, glands, and endothelium. In nasal provocation studies, leu-AP correlated with glandular exocytosis but not vascular leak.

CONCLUSIONS

The predominant aminopeptidase in human nasal epithelial and submucosal gland cells was membrane-bound puromycin-resistant aminopeptidase. A novel soluble puromycin-resistant aminopeptidase and lower amounts of soluble PS-Ap were also detected.