Otopathogenic Staphylococcus aureus Invades Human Middle Ear Epithelial Cells Primarily through Cholesterol Dependent Pathway.

Chronic suppurative otitis media (CSOM) is one of the most common infectious diseases of the middle ear especially affecting children, leading to delay in language development and communication. Although Staphylococcus aureus is the most common pathogen associated with CSOM, its interaction with middle ear epithelial cells is not well known. In the present study, we observed that otopathogenic S. aureus has the ability to invade human middle ear epithelial cells (HMEECs) in a dose and time dependent manner. Scanning electron microscopy demonstrated time dependent increase in the number of S. aureus on the surface of HMEECs. We observed that otopathogenic S. aureus primarily employs a cholesterol dependent pathway to colonize HMEECs. In agreement with these findings, confocal microscopy showed that S. aureus colocalized with lipid rafts in HMEECs. The results of the present study provide new insights into the pathogenesis of S. aureus induced CSOM. The availability of in vitro cell culture model will pave the way to develop novel effective treatment modalities for CSOM beyond antibiotic therapy.

Recent advancements in nanoparticle based drug delivery for gastrointestinal disorders.

INTRODUCTION: The emergent field of nanoparticles has presented a wealth of opportunities for improving the treatment of human diseases. Recent advances have allowed for promising developments in drug delivery, diagnostics, and therapeutics. Modified delivery systems allow improved drug delivery over traditional pH, microbe, or receptor dependent models, while antibody association allows for more advanced imaging modalities. Nanoparticles have potential clinical application in the field of gastroenterology as they offer several advantages compared to the conventional treatment systems including target drug delivery, enhanced treatment efficacy, and reduced side effects. AREAS COVERED: The aim of this review article is to summarize the recent advancements in developing nanoparticle technologies to treat gastrointestinal diseases. We have covered the application of nanoparticles in various gastrointestinal disorders including inflammatory bowel disease and colorectal cancer. We also have discussed how the gut microbiota affects the nanoparticle based drug delivery in the gastrointestinal tract. EXPERT OPINION: Nanoparticles based drug delivery offers a great platform for targeted drug delivery for gastrointestinal disorders. However, it is influenced by the presence of microbiota, drug interaction with nanoparticles, and cytotoxicity of nanoparticles. With the advancements in nanoparticle technology, it may be possible to overcome these barriers leading to efficient drug delivery for gastrointestinal disorders based on nanoparticle platform.

Neurotransmitters: The Critical Modulators Regulating Gut-Brain Axis.

Neurotransmitters, including catecholamines and serotonin, play a crucial role in maintaining homeostasis in the human body. Studies on these neurotransmitters mainly revolved around their role in the "fight or flight" response, transmitting signals across a chemical synapse and modulating blood flow throughout the body. However, recent research has demonstrated that neurotransmitters can play a significant role in the gastrointestinal (GI) physiology. Norepinephrine (NE), epinephrine (E), dopamine (DA), and serotonin have recently been a topic of interest because of their roles in the gut physiology and their potential roles in GI and central nervous system pathophysiology. These neurotransmitters are able to regulate and control not only blood flow, but also affect gut motility, nutrient absorption, GI innate immune system, and the microbiome. Furthermore, in pathological states, such as inflammatory bowel disease (IBD) and Parkinson's disease, the levels of these neurotransmitters are dysregulated, therefore causing a variety of GI symptoms. Research in this field has shown that exogenous manipulation of catecholamine serum concentrations can help in decreasing symptomology and/or disease progression. In this review article, we discuss the current state-of-the-art research and literature regarding the role of neurotransmitters in regulation of normal GI physiology, their impact on several disease processes, and novel work focused on the use of exogenous hormones and/or psychotropic medications to improve disease symptomology. J. Cell. Physiol. 232: 2359-2372, 2017. © 2016 Wiley Periodicals, Inc.

Intricate Functions of Matrix Metalloproteinases in Physiological and Pathological Conditions.

Matrix metalloproteinases (MMPs) are a diverse group of proteolytic enzymes and play an important role in the degradation and remodeling of the extracellular matrix (ECM). In normal physiological conditions, MMPs are usually minimally expressed. Despite their low expression, MMPs have been implicated in many cellular processes ranging from embryological development to apoptosis. The activity of MMPs is controlled at three different stages: (1) transcription; (2) zymogen activation; and (3) inhibition of active forms by tissue inhibitor metalloproteinases (TIMPs). They can collectively degrade any component of ECM and basement membrane, and their excessive activity has been linked to numerous pathologies mainly including, but not limited to, tumor invasion and metastasis. The lack of information about several MMPs and the steady stream of new discoveries suggest that there is much more to be studied in this field. In particular, there is a need for controlling their expression in disease states. Various studies over the past 30 years have found that each MMP has a specific mode of activation, action, and inhibition. Drugs specifically targeting individual MMPs could revolutionize the treatment of a great number of health conditions and tremendously reduce their burden. In this review article, we have summarized the recent advances in understanding the role of MMPs in physiological and pathological conditions. J. Cell. Physiol. 231: 2599-2621, 2016. © 2016 Wiley Periodicals, Inc.

Molecular Structure and Regulation of P2X Receptors With a Special Emphasis on the Role of P2X2 in the Auditory System.

The P2X purinergic receptors are cation-selective channels gated by extracellular adenosine 5'-triphosphate (ATP). These purinergic receptors are found in virtually all mammalian cell types and facilitate a number of important physiological processes. Within the past few years, the characterization of crystal structures of the zebrafish P2X4 receptor in its closed and open states has provided critical insights into the mechanisms of ligand binding and channel activation. Understanding of this gating mechanism has facilitated to design and interpret new modeling and structure-function experiments to better elucidate how different agonists and antagonists can affect the receptor with differing levels of potency. This review summarizes the current knowledge on the structure, activation, allosteric modulators, function, and location of the different P2X receptors. Moreover, an emphasis on the P2X2 receptors has been placed in respect to its role in the auditory system. In particular, the discovery of three missense mutations in P2X2 receptors could become important areas of study in the field of gene therapy to treat progressive and noise-induced hearing loss. J. Cell. Physiol. 231: 1656-1670, 2016. © 2015 Wiley Periodicals, Inc.