K_ATP Channel Openers Inhibit Lymphatic Contractions and Lymph Flow as a Possible Mechanism of Peripheral Edema

Abstract

Pharmacological openers of adenosine triphosphate-sensitive K + (K ATP) channels are effective antihypertensive agents, but off-target effects, including severe peripheral edema limit their clinical usefulness. It is presumed that the arterial dilation induced by K ATP channel openers (KCOs) increases capillary pressure to promote filtration edema. However, K ATP channels also are expressed by lymphatic muscle cells (LMCs), raising the possibility that KCOs also attenuate lymph flow to increase interstitial fluid. The present study explored the effect of KCOs on lymphatic contractile function and lymph flow. In isolated rat mesenteric lymph vessels (LVs), the prototypic K ATP channel opener cromakalim (0.01-3 µmol/L) progressively inhibited rhythmic contractions and calculated intraluminal flow. Minoxidil sulfate and diazoxide (0.01-100 µmol/L) had similar effects at clinically relevant plasma concentrations. High speed in-vivo imaging of the rat mesenteric lymphatic circulation revealed that superfusion of LVs with cromakalim and minoxidil sulfate (0.01-10 µmol/L) maximally decreased lymph flow in vivo by 38.4% and 27.4%, respectively. Real-time PCR and flow cytometry identified the abundant K ATP channel subunits in LMCs as the pore-forming Kir6.1/6.2 and regulatory SUR2 subunits. Patch-clamp studies detected cromakalim-elicited unitary K + currents in cell-attached patches of LMCs with a single-channel conductance of 46.4 pS, a property consistent with Kir6.1/6.2 tetrameric channels. Addition of minoxidil sulfate and diazoxide elicited unitary currents of similar amplitude. Collectively, our findings indicate that KCOs attenuate lymph flow at clinically relevant plasma concentrations as a potential contributing mechanism to peripheral edema. Significance Statement Potassium channel openers (KCOs) are potent antihypertensive medications, but off-target effects including severe peripheral edema limit their clinical use. Here, we demonstrate that KCOs impair the rhythmic contractions of lymph vessels and attenuate lymph flow, which may promote edema formation. Our finding that the K ATP channels in lymphatic muscle cells may be unique from their counterparts in This article has not been copyedited and formatted. The final version may differ from this version.

Dantrolene Prevents the Lymphostasis Caused by Doxorubicin in the Rat Mesenteric Circulation

“…The resuspension step was repeated twice to eliminate residual enzymes from the cell suspension solution. Previous studies by us have shown that this method of LMC isolation produces individual cells for analysis (Garner et al, 2021).…”

“…Lymph flow was recorded continuously prior to and during the 20 min incubation period with DANT and for 60 min after rapid infusion of DOX. Customized software tracked individual lymph cells in flow as described in detail earlier by us (Sarimollaoglu et al, 2018;Stolarz et al, 2019;Garner et al, 2021). Using these data files, flow velocity and positive volumetric flow were calculated to evaluate the effects of DOX and DANT on lymph flow in vivo.…”

Drug-Related Lymphedema: Mysteries, Mechanisms, and Potential Therapies

“…Glibenclamide -induced block of these channels reportedly depolarizes guinea pig lymph muscle cells but has little to no effect on contractions of isolated rat mesenteric lymph vessels and isolated human thoracic ducts (Mizuno et al, 1999;Mathias and von der Weid, 2013;Telinius et al, 2014b). Although K ATP channels may be inactive under some conditions, they can cause hyperpolarization, inhibition of rhythmic contractions, and loss of lymph flow when activated by pharmacological agents or gain-of-function mutations (Mathias and von der Weid, 2013;Davis et al, 2020;Garner et al, 2021).…”

Lymphatic Collecting Vessel: New Perspectives on Mechanisms of Contractile Regulation and Potential Lymphatic Contractile Pathways to Target in Obesity and Metabolic Diseases

“…In LMCs, as with most smooth muscle, K + permeability is critical for resting membrane potential regulation ( Ohhashi and Azuma, 1982 ; Telinius et al, 2014a ) that governs the muscle excitability and contractile activity. Hyperpolarization by elevated K + conductance can either overwhelm the depolarizing influence of inwards currents, such as those provided by Ano1, to prevent or slow the depolarization to the critical threshold, or with excessive K + currents hyperpolarize the membrane out of the voltage window permissive for rhythmic oscillations ( Mizuno et al, 1999 ; Mathias and von der Weid, 2013 ; Davis et al, 2020 ; Garner et al, 2021 ; Kim et al, 2021 ). Four different classes of K + channels have been identified in LMCs: Ca 2+ -activated K + channels, volage-dependent K + changes, ATP-sensitive K channels (K ATP ), and inward rectifier K + .…”

“…K ATP channels appear to be partially or transiently active under the resting condition in lymphatic vessels as glibenclamide (FDA-approved K ATP antagonist) increases the lymphatic contractile frequency in the human thoracic duct ( Telinius et al, 2014a ; Davis et al, 2020 ). Open K ATP channels prevent action potential generation in lymphatic vessels resulting in phasic contraction cessation, and clinically relevant concentrations of K ATP channel may impair in vivo lymphatic contractile function ( Garner et al, 2021 ). A relatively small alteration of resting membrane potential (e.g., 4mV) through K ATP modulation is enough to initiate lymphatic phasic contraction from quiescent vessels ( Telinius et al, 2014a ) or cease electrical and contractile activity ( Davis et al, 2020 ), indicating the powerful role of K ATP as a mediator lymphatic contractile dysfunction.…”