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Calcium desensitisation in late polymicrobial sepsis is associated with loss of vasopressor sensitivity in a murine model
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 (R...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Springer International Publishing
2015
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4512972/ https://www.ncbi.nlm.nih.gov/pubmed/26215803 http://dx.doi.org/10.1186/s40635-014-0036-8 |
Sumario: | 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, Ca(v)1.2 Ca(2+) channels (LTCC)), (ii) thromboxane A(2) 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) α(1)-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 A(2) receptor activation and PKC activation (n = 8 to 13; p < 0.05). α(1)-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 A(2) receptor activation and PKC activation were diminished in vitro whilst α(1)-adrenergic responses remained intact. Inhibiting MLCP may present a novel therapeutic target to manage sepsis-induced vascular dysfunction. |
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