Neuroendocrine influence on thymic haematopoiesis via the reticulo-epithelial cellular network

Approaches to Address PK-PD Challenges of Conventional Liposome Formulation with Special Reference to Cancer, Alzheimer's, Diabetes, and Glaucoma: An Update on Modified Liposomal Drug Delivery System

Liposomes nowadays have become a preferential drug delivery system since they provide facilitating properties to drugs, such as improved therapeutic index of encapsulated drug, target and controlled drug delivery, and less toxicity. However, conventional liposomes have shown some disadvantages, such as less drug loading capacity, poor retention, clearance by kidney or reticuloendothelial system, and less release of hydrophilic drugs. Thus, to overcome these disadvantages recently, scientists have explored new approaches and methods, viz., ligand conjugation, polymer coating, and liposome hybrids, including surface-modified liposomes, biopolymer-incorporated liposomes, guest-in-cyclodextrin-in-liposome, liposome-in-hydrogel, liposome-in-film, liposome-in-nanofiber, etc. These approaches have been shown to improve the physiochemical and pharmacokinetic properties of encapsulated drugs. Lately, pharmacokinetic-pharmacodynamic (PK-PD) computational modeling has emerged as a beneficial tool for analyzing the impact of formulation and system-specific factors on the target disposition and therapeutic efficacy of liposomal drugs. There has been an increasing number of liposome-based therapeutic drugs, both FDA approved and those undergoing clinical trials, having application in cancer, Alzheimer's, diabetes, and glaucoma. To meet the continuous demand of health sectors and to produce the desired product, it is important to perform pharmacokinetic studies. This review focuses on the physical, physicochemical, and chemical factors of drugs that influence the target delivery of drugs. It also explains various physiological barriers, such as systemic clearance and extravasation. A novel approach, liposomal-hybrid complex, an innovative approach as a vesicular drug delivery system to overcome limited membrane permeability and bioavailability, has been discussed in the review. Moreover, this review highlights the pharmacokinetic considerations and challenges of poorly absorbed drugs along with the applications of a liposomal delivery system in improving PKPD in various diseases, such as cancer, Alzheimer's, diabetes, and glaucoma.

Carboxypeptidase E, an essential element of the regulated secretory pathway, is expressed and partially co-localized with chromogranin A in chicken thymus

Although the functions of hormones and neuropeptides in the thymus have been extensively studied, we still do not know whether these intra-thymic humoral elements are released in a stimulated manner via the regulated secretory pathway or in a constitutive manner. Carboxypeptidase E (CpE) and chromogranin A (CgA) are functional and structural hallmarks of the regulated secretory pathway in (neuro)endocrine cells. Whereas we have previously shown a CgA-positive neuroendocrine population in the chicken thymus, the current study assesses the expression of CpE in the thymus, both at the mRNA and the protein level. Our immunohistochemical studies provide evidence for the co-existence of CgA and CpE in identical neuroendocrine cells in the thymus. CpE and CgA dual-positive cells have primarily been found in the transition zone between the cortex and medulla of the thymus, an area known to contain numerous arterioles and to be innervated by the autonomic nervous system. Our findings suggest that the diffuse neuroendocrine system serves as a relay for nervous stimuli delivered by the sympathetic and/or parasympathetic nervous system. Thus, these newly defined neuroendocrine cells might play an important role in the immuno-neuro-endocrine cross-talk in the thymus, potentially enabling thymopoiesis to be fine-tuned via the regulated secretory pathway by a variety of physical and environmental factors.