Ololade Ogunsina

Background/Objectives: We reported previously that antagonists at chemokine receptors CCR2 and CCR3 have fluid-sparing effects during resuscitation from hemorrhagic shock. Because CCR1 shares several chemokine ligands with CCR2/3, we tested whether the CCR1 antagonist BX471 also reduces fluid requirements to maintain hemodynamics. Methods: Sprague Dawley rats were hemorrhaged for 30 min, followed by fluid resuscitation to maintain blood pressure for 60 min (series 1) and 180 min (series 2). Series 1: Animals received vehicle (n = 5), 0.05 μmol/kg (n = 5), or 0.5 μmol/kg (n = 4) BX471 at t = 30 min. Series 2: Animals received vehicle (n = 8) or 0.5 μmol/kg (n = 7) BX471 at t = 30 min. Hemodynamics, fluid requirements, blood gases, and lactate were monitored. Serum concentrations of CCR1 ligands (CCL3/4/5/7) were determined at baseline and at the conclusion of the experiments. Tissue (small/large intestine, lung) wet/dry (W/D) weight ratios, lung myeloperoxidase activity, and a panel of inflammation markers in tissue extracts were measured. Results: All animals could be resuscitated to target blood pressures. Series 1: A total of 0.5 μmol/kg BX471 reduced fluid requirements by more than 60% (p < 0.05 vs. vehicle and 0.05 μmol/kg BX471). Series 2: Systemic CCL3/5/7 levels increased during the experiment (p < 0.05). BX471-treatment reduced fluid requirements by more than 60% (p < 0.05) and prevented increases in CCL3/7. W/D ratios of large intestine and of the sum of all tissues were lower with BX471 treatment (p < 0.05). BX471-treatment reduced TNFα and IL6 concentrations in large intestine extracts (p < 0.05). Conclusions: Our findings suggest CCR1 as a new therapeutic target to reduce fluid requirements during resuscitation from hemorrhagic shock.

β-adrenoceptor (β-AR) agonists are known to antagonize thrombin-induced impairment (TII) of bovine and ovine lung endothelial barrier function. The effects of adrenoceptor agonists and other vasoactive agents on human lung microvascular endothelial cell (HULEC-5a) barrier function upon thrombin exposure have not been studied. Furthermore, it is unknown whether the in vitro effects of adrenoceptor agonists translate to lung protective effects in vivo. We observed that epinephrine, norepinephrine, and phenylephrine enhanced normal and prevented TII of HULEC-5a barrier function. Arginine vasopressin and angiotensin II were ineffective. α_1B-, α_2A/B-, and β_1/2-ARs were detectable in HULEC-5a by RT-PCR. Propranolol but not doxazosin blocked the effects of all adrenoceptor agonists. Phenylephrine stimulated β₂-AR-mediated Gαs activation with 13-fold lower potency than epinephrine. The EC₅₀ to inhibit TII of HULEC-5a barrier function was 1.8 ± 1.9 nM for epinephrine and >100 nM for phenylephrine. After hemorrhagic shock and fluid resuscitation in rats, Evans blue extravasation into the lung increased threefold (p < 0.01 vs. sham). Single low-dose (1.8 μg/kg) epinephrine administration at the beginning of resuscitation had no effects on blood pressure and reduced Evans blue extravasation by 60% (p < 0.05 vs. vehicle). Our findings confirm the effects of β-adrenoceptor agonists in HULEC-5a and suggest that low-dose β-adrenoceptor agonist treatment protects lung vascular barrier function after traumatic hemorrhagic shock.