Transporters influence the disposition of chemicals within the body by participating in absorption, distribution, and elimination. Transporters of the solute carrier family (SLC) comprise a variety of proteins, including organic cation transporters (OCT) 1 to 3, organic cation/carnitine transporters (OCTN) 1 to 3, organic anion transporters (OAT) 1 to 7, various organic anion transporting polypeptide isoforms, sodium taurocholate cotransporting polypeptide, apical sodium-dependent bile acid transporter, peptide transporters (PEPT) 1 and 2, concentrative nucleoside transporters (CNT) 1 to 3, equilibrative nucleoside transporter (ENT) 1 to 3, and multidrug and toxin extrusion transporters (MATE) 1 and 2, which mediate the uptake (except MATEs) of organic anions and cations as well as peptides and nucleosides. Efflux transporters of the ATP-binding cassette superfamily, such as ATP-binding cassette transporter A1 (ABCA1), multidrug resistance proteins (MDR) 1 and 2, bile salt export pump, multidrug resistance-associated proteins (MRP) 1 to 9, breast cancer resistance protein, and ATP-binding cassette subfamily G members 5 and 8, are responsible for the unidirectional export of endogenous and exogenous substances. Other efflux transporters [ATPase copper-transporting β polypeptide (ATP7B) and ATPase class I type 8B member 1 (ATP8B1) as well as organic solute transporters (OST) α and β] also play major roles in the transport of some endogenous chemicals across biological membranes. This review article provides a comprehensive overview of these transporters (both rodent and human) with regard to tissue distribution, subcellular localization, and substrate preferences. Because uptake and efflux transporters are expressed in multiple cell types, the roles of transporters in a variety of tissues, including the liver, kidneys, intestine, brain, heart, placenta, mammary glands, immune cells, and testes are discussed. Attention is also placed upon a variety of regulatory factors that influence transporter expression and function, including transcriptional activation and post-translational modifications as well as subcellular trafficking. Sex differences, ontogeny, and pharmacological and toxicological regulation of transporters are also addressed. Transporters are important transmembrane proteins that mediate the cellular entry and exit of a wide range of substrates throughout the body and thereby play important roles in human physiology, pharmacology, pathology, and toxicology.

Xenobiotic, Bile Acid, and Cholesterol Transporters: Function and Regulation

Immunologic mechanisms in asthma.

Banana (Musa spp) from peel to pulp: ethnopharmacology, source of bioactive compounds and its relevance for human health.

Tight junction modulation by chitosan nanoparticles: comparison with chitosan solution.

Intranasal delivery has been shown to non-invasively deliver drugs from the nose to the brain in minutes along the olfactory and trigeminal nerve pathways, bypassing the blood-brain barrier. However, no one has investigated whether nasally applied drugs target orofacial structures, despite high concentrations observed in the trigeminal nerve innervating these tissues. Following intranasal administration of lidocaine to rats, trigeminally-innervated structures (teeth, temporomandibular joint (TMJ), and masseter muscle) were found to have up to 20-fold higher tissue concentrations of lidocaine than the brain and blood as measured by ELISA. This concentration difference could allow intranasally administered therapeutics to treat disorders of orofacial structures (i.e. teeth, TMJ, and masseter muscle) without causing unwanted side effects in the brain and the rest of the body. In this study, an intranasally administered infrared dye reached the brain within 10 minutes. Distribution of dye is consistent with dye entering the trigeminal nerve after intranasal administration through three regions with high drug concentrations in the nasal cavity: the middle concha, the maxillary sinus, and the choana. In humans the trigeminal nerve passes through the maxillary sinus to innervate the maxillary teeth. Delivering lidocaine intranasally may provide an effective anesthetic technique for a non-invasive maxillary nerve block. Intranasal delivery could be used to target vaccinations and treat disorders with fewer side effects such as tooth pain, TMJ disorder, trigeminal neuralgia, headache, and brain diseases.

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Trigeminal Pathways Deliver a Low Molecular Weight Drug from the Nose to the Brain and Orofacial Structures

Comparison of human tracheal/bronchial epithelial cell culture and bovine nasal respiratory explants for nasal drug transport studies

Dopamine has poor oral bioavailability and low permeability across the blood–brain barrier, and yet it has been reported to have good systemic and central nervous system (CNS) bioavailability following nasal administration. The aim of this study was to investigate the extent to which dopamine transport in the olfactory and respiratory mucosae results from the activity of organic cation transporters (OCTs) present in the nasal cavity. Transport studies were carried out to determine the mechanism of dopamine transport across bovine olfactory and nasal respiratory mucosa. Western blotting and immunohistochemistry were performed to determine the expression and localization of organic cation transporter-2, a major transporter of dopamine, in the nasal mucosa. Dopamine transport was found to be saturable across both tissues. Amantadine, an organic cation transporter-1 (OCT-1) and organic cation transporter-2 (OCT-2) mixed inhibitor, decreased dopamine flux to a greater extent than guanidine, a more specific org...

Role of organic cation transporters in dopamine uptake across olfactory and nasal respiratory tissues.

Role of dopamine transporter (DAT) in dopamine transport across the nasal mucosa

Metabolism of dopamine by the nasal mucosa.

Given the recent success of gene therapy modalities and the growing number of cell and gene-based therapies in clinical development across many different therapeutic areas, it is evident that this evolving field holds great promise for the unmet medical needs of patients. The recent approvals of Luxturna® and Zolgensma® prove that recombinant adeno-associated virus (rAAV)-based gene therapy is a transformative modality that enables curative treatment for genetic disorders. Over the last decade, Takeda has accumulated significant experience with rAAV-based gene therapies, especially in the early stage of development. In this review, based on the learnings from Takeda and publicly available information, we aim to provide a guiding perspective on Drug Metabolism and Pharmacokinetics (DMPK) substantial role in advancing therapeutic gene therapy modalities from nonclinical research to clinical development, in particular the characterization of gene therapy product biodistribution, elimination (shedding), immunogenicity assessment, multiple platform bioanalytical assays, and first-in-human (FIH) dose projection strategies. Graphical abstract

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Nagendra V. Chemuturi

Papers

Comparison of human tracheal/bronchial epithelial cell culture and bovine nasal respiratory explants for nasal drug transport studies

Role of organic cation transporters in dopamine uptake across olfactory and nasal respiratory tissues.

Role of dopamine transporter (DAT) in dopamine transport across the nasal mucosa

Metabolism of dopamine by the nasal mucosa.

The Perspective of DMPK on Recombinant Adeno-Associated Virus-Based Gene Therapy: Past Learning, Current Support, and Future Contribution