Endogenous FGFs drive ERK-dependent cell fate patterning in 2D human gastruloids.

The role of FGF is the least understood of the morphogens driving mammalian gastrulation. Here we investigated the function of FGF in a stem cell model for human gastrulation known as a 2D gastruloid. We found a ring of FGF-dependent ERK activity that closely follows the emergence of primitive streak (PS)-like cells but expands further inward. We showed that this ERK activity pattern is required for PS-like differentiation and that loss of PS-like cells upon FGF receptor inhibition can be rescued by directly activating ERK. We further demonstrated that the ERK-ring depends on localized activation of basally localized FGF receptors (FGFR) by endogenous FGF gradients. We confirm and extend previous studies in analyzing expression of FGF pathway components, showing the main receptor to be FGFR1 and the key ligands FGF2/4/17, similar to the human and monkey embryo but different from the mouse. In situ hybridization and scRNA-seq revealed that FGF4 and FGF17 expression colocalize with the PS marker TBXT but only FGF17 is maintained in nascent mesoderm and endoderm. FGF4 and FGF17 reduction both reduced ERK activity and differentiation to PS-like cells and their derivatives, indicating overlapping function. Thus, we have identified a previously unknown role for FGF-dependent ERK signaling in 2D gastruloids and possibly the human embryo, driven by a mechanism where FGF4 and FGF17 signal through basally localized FGFR1 to induce PS-like cells.

Pregnane X Receptor Signaling Pathway and Vitamin K: Molecular Mechanisms and Clinical Relevance in Human Health.

This review explores the likely clinical impact of Pregnane X Receptor (PXR) activation by vitamin K on human health. PXR, initially recognized as a master regulator of xenobiotic metabolism in liver, emerges as a key regulator influencing intestinal homeostasis, inflammation, oxidative stress, and autophagy. The activation of PXR by vitamin K highlights its role as a potent endogenous and local agonist with diverse clinical implications. Recent research suggests that the vitamin K-mediated activation of PXR highlights this vitamin's potential in addressing pathophysiological conditions by promoting hepatic detoxification, fortifying gut barrier integrity, and controlling pro-inflammatory and apoptotic pathways. PXR activation by vitamin K provides an intricate association with cancer cell survival, particularly in colorectal and liver cancers, to provide new insights into potential novel therapeutic strategies. Understanding the clinical implications of PXR activation by vitamin K bridges molecular mechanisms with health outcomes, further offering personalized therapeutic approaches for complex diseases.

Management of Sjogren's Dry Eye Disease-Advances in Ocular Drug Delivery Offering a New Hope.

Sjögren's syndrome is a chronic and insidious autoimmune disease characterized by lymphocyte infiltration of exocrine glands. Patients typically present with dry eye, dry mouth, and other systemic manifestations. Currently, the available molecules and drug-delivery systems for the treatment of Sjögren's syndrome dry eye (SSDE) have limited efficacy since they are not specific to SSDE but to dry eye disease (DED) in general. The current treatment modalities are based on a trial-and-error approach using primarily topical agents. However, this approach gives time for the vicious cycle of DED to develop which eventually causes permanent damage to the lacrimal functional unit. Thus, there is a need for more individualized, specific, and effective treatment modalities for SSDE. The purpose of this article is to describe the current conventional SSDE treatment modalities and to expose new advances in ocular drug delivery for treating SSDE. A literature review of the pre-clinical and clinical studies published between 2016 and 2022 was conducted. Our current understanding of SSDE pathophysiology combined with advances in ocular drug delivery and novel therapeutics will allow the translation of innovative molecular therapeutics from the bench to the bedside.

Retinal lipid and glucose metabolism dictates angiogenesis through the lipid sensor Ffar1.

Tissues with high metabolic rates often use lipids, as well as glucose, for energy, conferring a survival advantage during feast and famine. Current dogma suggests that high-energy-consuming photoreceptors depend on glucose. Here we show that the retina also uses fatty acid ß-oxidation for energy. Moreover, we identify a lipid sensor, free fatty acid receptor 1 (Ffar1), that curbs glucose uptake when fatty acids are available. Very-low-density lipoprotein receptor (Vldlr), which is present in photoreceptors and is expressed in other tissues with a high metabolic rate, facilitates the uptake of triglyceride-derived fatty acid. In the retinas of Vldlr(-/-) mice with low fatty acid uptake but high circulating lipid levels, we found that Ffar1 suppresses expression of the glucose transporter Glut1. Impaired glucose entry into photoreceptors results in a dual (lipid and glucose) fuel shortage and a reduction in the levels of the Krebs cycle intermediate α-ketoglutarate (α-KG). Low α-KG levels promotes stabilization of hypoxia-induced factor 1a (Hif1a) and secretion of vascular endothelial growth factor A (Vegfa) by starved Vldlr(-/-) photoreceptors, leading to neovascularization. The aberrant vessels in the Vldlr(-/-) retinas, which invade normally avascular photoreceptors, are reminiscent of the vascular defects in retinal angiomatous proliferation, a subset of neovascular age-related macular degeneration (AMD), which is associated with high vitreous VEGFA levels in humans. Dysregulated lipid and glucose photoreceptor energy metabolism may therefore be a driving force in macular telangiectasia, neovascular AMD and other retinal diseases.

Separation and trace estimation of benzidine and its macromolecular adducts using supercritical fluid chromatography.

A sensitive, rapid, selective and reproducible method has been developed to measure blood plasma levels of benzidine (BZ) and its acetylated metabolite, N-OH-N,N'-diacetylbenzidine (N-OH-DABZ), using supercritical fluid chromatography (SFC) for the first time. Benzidine and N-OH-N,N'-diacetylbenzidine were extracted from the plasma using ether. Separation was done on a Nucleosil (250 mm x 4.6 mm) 10 microm, Nucleosil-RP-C18 column with 7.4% (v/v) methanol-modified supercritical fluid carbon dioxide (2.5 ml min(-1)) as mobile phase. The column temperature was 45 degrees C and the outlet pressure was set at 8.83 MPa. The detection was done using a UV-Vis detector set at 280 nm. The limit of quantification was 0.10 ng ml(-1) (BZ) and 0.14 ng ml(-1) (N-OH-diacetylbenzidine) using 1 ml plasma specimen. The mean extraction recovery of BZ was found to be 98.6%. The SFC method was directly compared to a published HPLC-UV method. With respect to speed, organic solvent usage, sensitivity, specificity and accuracy, SFC was found to be superior. The method has been successfully used to estimate the BZ, N-OH-diacetylbenzidine levels in blood plasma of the animals who were administered 15 microg kg(-1) body weight of benzidine.Further, this method has been also applied for the detection and quantification of benzidine DNA and hemoglobin adducts from the blood and tissue samples of the benzidine dosed animals.