Biology subjects

Welsh, D. G.

Publications and source records attributed to Welsh, D. G..

7 recordsLinked to original sources

bioRxiv2026

Connexin 40 deficiency alters the temporal profile of postictal oxygen dynamics following focal seizures.

Epilepsy is increasingly recognized as a disorder involving both neuronal and vascular dysfunction. While connexin signaling has been implicated in epileptogenesis, the contribution of vascular connexins to seizure associated cerebrovascular pathology remains poorly understood. Connexin40 (Cx40) is an endothelial gap junction protein that plays a crucial role in vascular communication and blood-flow regulation. Seizures induce dynamic changes in cerebral perfusion and oxygenation, including prolonged postictal hypoperfusion/hypoxia. To determine whether Cx40 influences postictal hypoxia following focal seizures, we examined seizure characteristics and postictal oxygen dynamics in Cx40 knockout (Cx40-/-) mice using an established focal hippocampal seizure model. Electrically kindled seizures were elicited in wild-type and Cx40-/- mice, and local hippocampal tissue oxygenation was continuously monitored before and after seizure induction. Seizure duration did not differ between genotypes, indicating comparable seizure severity. Interestingly, Cx40 deletion altered the temporal pattern of postictal oxygen recovery, producing greater early hypoxia and a delayed secondary rebound in pO2 despite similar peak oxygen levels and overall hypoxic burden. These findings demonstrate that loss of Cx40 selectively alters the temporal profile of postictal oxygen dynamics without affecting seizure duration. Taken together, the results suggest that endothelial gap junctional communication contributes to postictal vascular recovery and identify Cx40 as a potential modulator of seizure associated neurovascular dysfunction.

neuroscience↗

bioRxiv2026

Blood Pressure Regulates Functional Coupling of L-Type Ca2+ Channels: Reimaging the Foundation of Cerebral Blood Flow Control.

The myogenic response is the key autoregulatory mechanism setting cerebral blood flow and its mechanistic foundation is intimately tied to depolarization and the voltage gating of L-type Ca2+ channels (CaV1.2). While critical, this study argues for an additional mechanism, that of pressure itself enhancing CaV1.2 activity via cooperative gating and perimembrane trafficking of channels subunits. These novel insights were pursued at the cell level using patch-clamp electrophysiology and advanced microscopy, and then functionally in pressurized arteries through measures of tone and intracellular [Ca2+]i. Key findings were confirmed in mutant mice with disrupted functional coupling and translated into arteries procured from human brain tissue. From cerebral blood flow simulations of semi-realistic microvascular networks, we predict that loss of this alternative mechanism leads to maldistribution of brain blood flow and potentially a diminishment of cognitive function. This study reveals previously unrecognized pressure-sensitive CaV1.2 regulatory mechanism that advances understanding of cerebral blood flow. SignificanceBlood pressure sets base arterial constriction - a response critical for blood flow control in brain. This response is tied to CaV1.2 channels and their presumptive and exclusive activation by voltage, reasoning now under great scrutiny. We establish herein with advance methods, a second mode of CaV1.2 pressure regulation, that of enhanced functional cooperativity among neighboring channels. This novel mechano-response is tied to PKC and its ability to set channel phosphorylation and CaV1.2 trafficking. CaV1.2 pressure regulation was observed in human tissues and its disruption (mutant mice) impaired myogenic tone in the presence of preserved voltage control. Cerebral microvascular modeling highlights that losing this mechanism destabilizes blood flow distribution in brain, the knock-on effect being comprised cognitive function.

physiology↗

bioRxiv2024

Functional Bias of Contractile Control in Mouse Resistance Arteries

BackgroundConstrictor agonists set vascular tone through two coupling processes, one tied to (electromechanical), the other independent (pharmacomechanical) of membrane potential (VM). This arrangement raises an intriguing query: are they variably recruited such that each agonist elicits a range of vasomotor signatures, functionally biased towards one mechanism or the other? This query underlies this study and our examination of agonist-induced arterial constriction. MethodsMouse mesenteric arteries were exposed to a classic Gq/11 (phenylephrine) or Gq/11/G12/13 (U46619) coupled receptor agonist, and responses monitored in the absence and presence of L-type Ca2+ channel/protein kinase inhibitors. Contractile work was supplemented with measures of protein phosphorylation, VM, and cytosolic Ca2+; conceptual insights were enhanced with computational modeling. ResultsEach constrictor elicited a response curve that was attenuated and rightward shifted by nifedipine, findings aligned with functional bias; electromechanical coupling preceded pharmacomechanical, the latters importance rising with agonist concentration. Ensuing contractile and phosphorylation (CPI-17 & MYPT1 (T-855 & T-697)) measures revealed phenylephrine-induced pharmacomechanical coupling was tied to protein kinase C (PKC), while U46619 was tied to both PKC and Rho-kinase. A switch to pharmacomechanical coupling dominance occurred when agonist superfusion was replaced with discrete application to a small portion of artery. This switch was predicted by electromechanical modeling and supported by direct measures of VM and cytosolic Ca2+. ConclusionsOur work illustrates that constrictor agonists elicit functionally biased responses and that arteries toggle among contractile mechanisms, dependent on receptor signal bias, structural/electrical properties, and how agents are applied. We discuss how hemodynamic control is intimately tied to functional bias in both health and disease states, including but not limited to arterial vasospasm. O_FIG O_LINKSMALLFIG WIDTH=164 HEIGHT=200 SRC="FIGDIR/small/588016v1_ufig1.gif" ALT="Figure 1"> View larger version (62K): org.highwire.dtl.DTLVardef@11632b9org.highwire.dtl.DTLVardef@5c1144org.highwire.dtl.DTLVardef@719b08org.highwire.dtl.DTLVardef@795ec3_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIAgonist-induced constrictor responses exhibit a "functional bias" toward electromechanical or pharmacomechanical coupling dependent on agent concentration and mode of application. C_LIO_LIElectromechanical coupling typically but not exclusively precedes pharmacomechanical, the latter rising to prominence with agent concentration. Pharmacomechanical coupling is mediated through receptor pathways linked to PKC and Rho-kinase, regulatory proteins that target the catalytic and targeting subunit of MLCP. C_LIO_LIFunctional bias is malleable and thus each agonist elicits a range of vasomotor signatures, each presumptively important in controlling blood flow delivery in space and time. C_LI

physiology↗

bioRxiv2023

CaV3.1 Channels Facilitate Calcium Wave Generation and Myogenic Tone Development in Mouse Mesenteric Arteries.

BackgroundThe myogenic response is the mechanism whereby intraluminal pressure elicits arterial constriction pursuant to the maintenance of tissue perfusion. Smooth muscle [Ca2+] is a key determinant of constriction, a process intimately tied to L-type (CaV1.2) Ca2+ channels. While important, other Ca2+ channels, in particular T-type, are expressed and could contribute to pressure regulation within defined voltage ranges. This study examined the role of one T-type Ca2+ channel using mesenteric arteries from C57BL/6 wild type and CaV3.1-/- mice. MethodsPatch-clamp electrophysiology, pressure myography, non-invasive blood pressure measurements and rapid Ca2+ imaging were employed to define the CaV3.1-/- phenotype relative to C57BL/6. Proximity ligation assay tested the closeness of CaV3.1 channels to inositol triphosphate receptors (IP3R). Nifedipine (0.3 M) and 2-APB (50 M) were used to block L-type Ca2+ channels and IP3Rs, respectively. ResultsInitial experiments confirmed the absence of CaV3.1 expression and whole-cell current in global deletion mice, a change that coincided with a reduction in systemic blood pressure. Mesenteric arteries from CaV3.1-/- mice produced less myogenic tone than C57BL/6, particularly at lower pressures (20-60 mmHg) where membrane potential is more hyperpolarized. This reduction in myogenic tone correlated with diminished Ca2+ wave generation in the CaV3.1-/- mice. These asynchronous events are dependent upon Ca2+ release from the sarcoplasmic reticulum which is insensitive to L-type Ca2+ channel blockade. A close physical association (<40 nm) between IP3R1 and CaV3.1 was confirmed by proximity ligation assay; blockade of IP3R in nifedipine-treated C57BL/6 arteries rendered a CaV3.1-/- contractile phenotype. ConclusionFindings indicate that Ca2+ influx through CaV3.1 channels contributes to myogenic tone development at hyperpolarized voltages by triggering a Ca2+-induced Ca2+ release mechanism tied to the sarcoplasmic reticulum. This study helps establish CaV3.1 as a potential therapeutic target in the control of blood pressure. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=160 SRC="FIGDIR/small/528095v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@1b3fe9forg.highwire.dtl.DTLVardef@11954borg.highwire.dtl.DTLVardef@607417org.highwire.dtl.DTLVardef@65964c_HPS_FORMAT_FIGEXP M_FIG C_FIG

systems biology↗

bioRxiv2020

Myogenic Vasoconstriction Requires Canonical Gq/11 Signaling of Angiotensin II Type 1a Receptor in Murine Vasculature

BackgroundThe myogenic response is an inherent vasoconstrictive property of resistance arteries to keep blood flow constant in response to increases in intravascular pressure. Angiotensin II (Ang II) type 1 receptors (AT1R) are broadly distributed, mechanoactivated receptors, which have been proposed to transduce myogenic vasoconstriction. However, the AT1R subtype(s) involved and their downstream G protein- and {beta}-arrestin-mediated signaling pathways are still elusive. ObjectiveTo characterize the function of AT1aR and AT1bR in the regulation of the myogenic response of resistance size arteries and possible downstream signaling cascades mediated by Gq/11 and/or {beta}-arrestins. MethodsWe used Agtr1a-/-, Agtr1b-/- and tamoxifen-inducible smooth muscle-specific AT1aR knockout mice (SM-Agtr1a mice). FR900359, [Sar1, Ile4, Ile8] Ang II (SII) and TRV120055 were used as selective Gq/11 protein inhibitor and biased agonists to activate non-canonical {beta}-arrestin and canonical Gq/11 signaling of the AT1R, respectively. ResultsMyogenic and Ang II-induced vasoconstrictions were diminished in the perfused renal vasculature of Agtr1a-/- and SM-Agtr1a mice. Similar results were observed in isolated pressurized mesenteric and cerebral arteries. Myogenic tone and Ang II-induced vasoconstrictions were normal in arteries from Agtr1b-/- mice. The Gq/11 blocker FR900359 decreased myogenic tone and Ang II vasoconstrictions while selective biased targeting of AT1R {beta}-arrestin signaling pathways had no effects. ConclusionThe present study demonstrates that myogenic arterial constriction requires Gq/11-dependent signaling pathways of mechanoactivated AT1aR but not G protein-independent, noncanonical alternative signaling pathways in the murine mesenteric, cerebral and renal circulation.

physiology↗

bioRxiv2019

Intercellular Conduction Optimizes Arterial Network Function and Conserves Blood Flow Homeostasis during Cerebrovascular Challenges

Cerebral arterial networks match blood flow delivery with neural activity. Neurovascular response begins with a stimulus and a focal change in vessel diameter, which by themselves is inconsequential to blood flow magnitude, until they spread and alter the contractile status of neighboring arterial segments. We sought to define the mechanisms underlying integrated vascular behavior and considered the role of intercellular electrical signalling in this phenomenon. Electron microscopic and histochemical analysis revealed the structural coupling of cerebrovascular cells and the expression of gap junctional subunits at the cell interfaces, enabling intercellular signaling among vascular cells. Indeed, robust vasomotor conduction was detected in human and mice cerebral arteries after focal vessel stimulation; a response attributed to endothelial gap junctional communication, as its genetic alteration attenuated this behavior. Conducted responses was observed to ascend from the penetrating arterioles, influencing the contractile status of cortical surface vessels, in a simulated model of cerebral arterial network. Ascending responses recognised in vivo after whisker stimulation, were significantly attenuated in mice with altered endothelial gap junctional signalling confirming that gap junctional communication drives integrated vessel responses. The diminishment in vascular communication also impaired the critical ability of the cerebral vasculature to maintain blood flow homeostasis and hence tissue viability, after stroke. Our findings establish the integral role of intercellular electrical signalling in transcribing focal stimuli into coordinated changes in cerebrovascular contractile activity and expose, a hitherto unknown mechanism for flow regulation after stroke.\n\nSignificanceNeurovascular responses are viewed as a one step process whereby stimuli derived from neural cells focally diffuse to a neighboring vessel, altering its contractile state. While focal changes in tone can subtly tune flow distribution, they cant substantively change \"perfusion magnitude\" as vascular resistance is broadly distributed along the cerebral arterial tree. We report that nature overcomes this biophysical constraint by conducting electrical signals among coupled vascular cells, along vessels, and across branch points. Our quantitative exploration of intercellular conduction illustrates how network coordination optimizes blood flow delivery in support of brain function. Diminishing the ability of vascular cells to electrically communicate, mitigates the brains ability to regulate perfusion during functional hyperemia and after stroke, the latter advancing tissue injury.

neuroscience↗

bioRxiv2018

Membrane Lipid-KIR2.x Channel Interactions Enable Hemodynamic Sensing in Cerebral Arteries

Inward rectifying (KIR) K+ channels are present in cerebral arterial smooth muscle and endothelial cells, a tandem arrangement suggestive of a dynamic yet undiscovered role for this channel. We explored whether vascular KIR channels were uniquely modulated by membrane lipids and hemodynamic stimuli. A KIR current was isolated in smooth muscle and endothelial cells of rat cerebral arteries and molecular analyses confirmed KIR2.1/KIR2.2 mRNA and protein expression. Electrophysiology next revealed that endothelial KIR was sensitive to phosphatidylinositol 4,5- bisphosphate (PIP2), with depletion impairing flow-induced activation of the channel. In contrast, smooth muscle KIR was sensitive to membrane cholesterol, with sequestration blocking pressures ability to inhibit this channel. Membrane lipids helped confer KIR mechanosensitivity to intact arteries; virtual models then reconceptualised KIR as a dynamic regulator of basal tone development. We conclude that specific membrane lipid-KIR interactions enable unique channel populations to sense hemodynamic stimuli and set brain perfusion.

neuroscience↗