Calcium desensitisation in late polymicrobial sepsis is associated with loss of vasopressor sensitivity in a murine model
Files
(Published version)
Date
2015
Authors
Reddi, B.
Beltrame, J.
Young, R.
Wilson, D.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
Intensive Care Medicine Experimental, 2015; 3(1):36-1-36-15
Statement of Responsibility
Benjamin AJ Reddi, John F Beltrame, Richard L Young, and David P Wilson
Conference Name
Abstract
BACKGROUND: Sepsis is characterised by diminished vasopressor responsiveness. Vasoconstriction depends upon a balance: Ca(2+)-dependent myosin light-chain kinase promotes and Ca(2+)-independent myosin light-chain phosphatase (MLCP) opposes vascular smooth muscle contraction. The enzyme Rho kinase (ROK) inhibits MLCP, favouring vasoconstriction. We tested the hypothesis that ROK-dependent MLCP inhibition was attenuated in late sepsis and associated with reduced contractile responses to certain vasopressor agents. METHODS: This is a prospective, controlled animal study. Sixteen-week-old C57/BL6 mice received laparotomy or laparotomy with caecal ligation and puncture (CLP). Antibiotics, fluids and analgesia were provided before sacrifice on day 5. Vasoconstriction of the femoral arteries to a range of stimuli was assessed using myography: (i) depolarisation with 87 mM K(+) assessed voltage-gated Ca(2+) channels (L-type, Cav1.2 Ca(2+) channels (LTCC)), (ii) thromboxane A2 receptor activation assessed the activation state of the LTCC and ROK/MLCP axis, (iii) direct PKC activation (phorbol-dibutyrate (PDBu), 5 μM) assessed the PKC/CPI-17 axis independent of Ca(2+) entry and (iv) α1-adrenoceptor stimulation with phenylephrine (10(-8) to 10(-4) M) and noradrenaline (10(-8) to 10(-4) M) assessed the sum of these pathways plus the role of the sarcoplasmic reticulum (SR). ROK-dependent MLCP activity was indexed by Western blot analysis of P[Thr855]MYPT. Parametric and non-parametric data were analysed using unpaired Student's t-tests and Mann-Whitney tests, respectively. RESULTS: ROK-dependent inhibition of MLCP activity was attenuated in both unstimulated (n = 6 to 7) and stimulated (n = 8 to 12) vessels from mice that had undergone CLP (p < 0.05). Vessels from CLP mice demonstrated reduced vasoconstriction to K(+), thromboxane A2 receptor activation and PKC activation (n = 8 to 13; p < 0.05). α1-adrenergic responses were unchanged (n = 7 to 12). CONCLUSIONS: In a murine model of sepsis, ROK-dependent inhibition of MLCP activity in vessels from septic mice was reduced. Responses to K(+) depolarisation, thromboxane A2 receptor activation and PKC activation were diminished in vitro whilst α1-adrenergic responses remained intact. Inhibiting MLCP may present a novel therapeutic target to manage sepsis-induced vascular dysfunction.
School/Discipline
Dissertation Note
Provenance
Description
Access Status
Rights
© 2015 Reddi et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.