Impaired lymphangiogenesis is a complication of chronic complex diseases, including diabetes. VEGF-C/VEGFR3 signaling promotes lymphangiogenesis, but how this pathway is affected in diabetes remains poorly understood. We previously demonstrated that loss of epsins 1 and 2 in lymphatic endothelial cells (LECs) prevented VEGF-C-induced VEGFR3 from endocytosis and degradation. Here, we report that diabetes attenuated VEGF-C-induced lymphangiogenesis in corneal micropocket and Matrigel plug assays in WT mice but not in mice with inducible lymphatic-specific deficiency of epsins 1 and 2 (LEC-iDKO). Consistently, LECs isolated from diabetic LEC-iDKO mice elevated in vitro proliferation, migration, and tube formation in response to VEGF-C over diabetic WT mice. Mechanistically, ROS produced in diabetes induced c-Src-dependent but VEGF-C-independent VEGFR3 phosphorylation, and upregulated epsins through the activation of transcription factor AP-1. Augmented epsins bound to and promoted degradation of newly synthesized VEGFR3 in the Golgi, resulting in reduced availability of VEGFR3 at the cell surface. Preclinically, the loss of lymphatic-specific epsins alleviated insufficient lymphangiogenesis and accelerated the resolution of tail edema in diabetic mice. Collectively, our studies indicate that inhibiting expression of epsins in diabetes protects VEGFR3 against degradation and ameliorates diabetes-triggered inhibition of lymphangiogenesis, thereby providing a novel potential therapeutic strategy to treat diabetic complications.

the spontaneous contractions of collecting lymphatic vessels provide an essential propulsive force to return lymph centrally. these contractions are driven by an intrinsic electrical pacemaker, working through an unknown underlying ionic mechanism that becomes compromised in some forms of lymphedema. in previous studies, t-type voltage-gated ca 2+ channels (VGccs) were implicated in this pacemaking mechanism, based on the effects of the reputedly selective T-type VGCC inhibitors mibefradil and ni 2+. Our goal was to test this idea in a more definitive way using genetic knock out mice. first, we demonstrated through both pcR and immunostaining that mouse lymphatic muscle cells expressed ca v 3.1 and Ca v 3.2 and produced functional T-type VGCC currents when patch clamped. We then employed genetic deletion strategies to selectively test the roles of each t-type VGcc isoform in the regulation of lymphatic pacemaking. Surprisingly, global deletion of either, or both, isoform(s) was without significant effect on either the frequency, amplitude, or fractional pump flow of lymphatic collectors from two different regions of the mouse, studied ex vivo. further, both Wt and ca v 3.1 −/− ; 3.2 −/− double knockout lymphatic vessels responded similarly to mibefradil and ni 2+ , which substantially reduced contraction amplitudes and slightly increased frequencies at almost all pressures in both strains: a pattern consistent with inhibition of L-type rather than t-type VGccs. Neither T-type VGCC isoform was required for ACh-induced inhibition of contraction, a mechanism by which those channels in smooth muscle are thought to be targets of endothelium-derived nitric oxide. Sharp intracellular electrode measurements in lymphatic smooth muscle revealed only subtle, but not significant, differences in the resting membrane potential and action potential characteristics between vessels from wild-type and ca v 3.1 −/− ; 3.2 −/− double knockout mice. in contrast, smoothmuscle specific deletion of the L-type VGCC, Ca v 1.2, completely abolished all lymphatic spontaneous contractions. collectively our results suggest that, although t-type VGccs are expressed in mouse lymphatic smooth muscle, they do not play a significant role in modulating the frequency of the ionic pacemaker or the amplitude of spontaneous contractions. We conclude that the effects of mibefradil and ni 2+ in other lymphatic preparations are largely or completely explained by off-target effects on L-type VGCCs, which are essential for controlling both the frequency and strength of spontaneous contractions. The spontaneous contractions of collecting lymphatic vessels propel lymph centrally to account for 2/3 of peripheral lymph flow 1,2. These rapid, large-amplitude contractions are analogous to twitch contractions of cardiac and skeletal muscle and are particularly important for moving lymph uphill against the adverse hydrostatic gradients that exist in dependent extremities. Lymphatic contractions are triggered by action potentials (APs) in lymphatic smooth muscle cell...

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Patients experiencing atrial fibrillation are at an increased risk for thromboembolic events. Therefore, anticoagulation therapy is imperative to prevent thrombus formation and stroke. Dabigatran etexilate was approved by the Food and Drug Administration in 2010 as anticoagulant prophylaxis for patients with nonvalvular atrial fibrillation. The frequency of dermatologic reactions to dabigatran etexilate is estimated in the product labeling to be less than 0.1%. To date, five cases of dabigatran etexilate-associated rash have reported, including three published cases. We describe the sixth reported case of dabigatran etexilate-associated rash, in a 59-year-old man with a history of atrial fibrillation who received dabigatran etexilate 150 mg twice/day for atrial flutter before cardioversion. The patient had taken dabigatran etexilate for 5 days before the rash was noted on hospital admission. He had no known previous drug allergies, and his platelet count, serum creatinine concentration, and hepatic function were normal. The rash resolved 7 days after the discontinuation of dabigatran etexilate, and the patient was stabilized on warfarin therapy. Use of the Naranjo Adverse Drug Reaction Probability Scale indicated a probable relationship (score of 5) between the patient's development of the rash and dabigatran etexilate therapy. Clinicians should be aware of this adverse effect of dabigatran etexilate and monitor for dermatologic reactions during follow-up visits.