MARCKS phosphorylation and amylase release in GLP-1-stimulated acini isolated from rat pancreas

An integrated approach identifies the molecular underpinnings of murine anterior visceral endoderm migration

The anterior visceral endoderm (AVE) differs from the surrounding visceral endoderm (VE) in its migratory behavior and ability to restrict primitive streak formation to the opposite side of the mouse embryo. To characterize the molecular bases for the unique properties of the AVE, we combined single-cell RNA sequencing of the VE prior to and during AVE migration with phosphoproteomics, high-resolution live-imaging, and short-term lineage labeling and intervention. This identified the transient nature of the AVE with attenuation of "anteriorizing" gene expression as cells migrate and the emergence of heterogeneities in transcriptional states relative to the AVE's position. Using cell communication analysis, we identified the requirement of semaphorin signaling for normal AVE migration. Lattice light-sheet microscopy showed that Sema6D mutants have abnormalities in basal projections and migration speed. These findings point to a tight coupling between transcriptional state and position of the AVE and identify molecular controllers of AVE migration.

Peptide Inhibitors of MARCKS Suppress Endotoxin Induced Uveitis in Rats

Purpose: To determine if inhibition of Myristoylated Alanine Rich C Kinase Substrate (MARCKS) protein, using novel MARCKS inhibitor peptides, will reduce the severity of endotoxin-induced uveitis (EIU) in rats. Methods: EIU was induced in Lewis rats using subcutaneous administration of lipopolysaccharide. In the first phase of the study, 3 different novel MARCKS inhibitor peptides that mimic the N-terminal region of MARCKS (BIO-11006, or lower molecular weight analogs BIO-91201 or BIO-91202; Biomarck Pharmaceuticals, Ltd., Newtown, PA) were administered intravitreally (IVT) at 50 and 100 μM. In the second phase, BIO-91201 was administered IVT at 10, 50, and 100 μM and topically at the 100 μM concentration. The efficacy of MARCKS inhibitor peptides was assessed by clinical examination using slit lamp biomicroscopy, optical coherence tomography (OCT) anterior chamber cell counts, histopathology, and aqueous humor cytokine analysis. Results: Clinical scores were significantly reduced 24 h following uveitis induction in the first phase of the study in the following treatment groups: BIO-11006 50 μM IVT and 100 μM IVT, BIO-91201 50 μM IVT, and BIO-91202 100 μM IVT (P < 0.05). OCT anterior chamber cell counts were significantly reduced in the first phase of the study in all treatment groups (P < 0.001). OCT anterior chamber cell counts and histopathology scores were significantly reduced in the second phase of the study in the BIO-91201 50 μM IVT group (P < 0.05). No effect was seen with topical administration. Conclusion: MARCKS inhibitor peptides were effective in reducing the severity of ocular inflammation and cellular influx in EIU.

The Effects of Trypsin Inhibitor on Insulin Secretion Using Rat Pancreas in an Organ Bath

BACKGROUND/AIM

We developed an experimental method to reproduce insulin secretion from isolated rat pancreas preparations using an organ bath system. However, secretion of trypsin, another pancreatic enzyme, interferes with insulin production in such systems. We aimed to ascertain the minimum trypsin inhibitor (TI), dose for obtaining a sustained, stable rate of insulin secretion.

MATERIALS AND METHODS

The action of TI (1-10 μg/ml) on pancreatic preparations of male Wistar-Imamichi rats in organ bath experiments was assessed by measuring insulin, amylase, and trypsin activity.

RESULTS

The level of insulin outflow remained steady in the TI-treated samples, in contrast to that in the untreated control, where insulin secretion decreased over time. The level of amylase outflow did not change significantly. Trypsin activity was significantly lower in the TI-treated samples than in the control.

CONCLUSION

Even low concentrations of TI can maintain insulin secretion by inhibiting trypsin activity in organ bath experiments.