Influence of ACTH‐(1–24) on free radical levels in the blood of haemorrhage‐shocked rats: direct ex vivo detection by electron spin resonance spectrometry

Abstract

The influence of ACTH‐(1–24) on the blood levels of highly reactive free radicals in haemorrhagic shock was studied in rats. Volume‐controlled haemorrhagic shock was produced in adult rats under general anaesthesia (urethane, 1.25 g kg−1 intraperitoneally) by stepwise bleeding until mean arterial pressure stabilized at 20–23 mmHg. Rats were intravenously (i.v.) treated with either ACTH‐(1–24) (160 μg kg−1 in a volume of 1 ml kg−1) or equivolume saline. Free radicals were measured in arterial blood by electron spin resonance spectrometry using an ex vivo method that avoids injection of the spin‐trapping agent (α‐phenyl‐N‐tert‐butylnitrone). Blood levels of free radicals were 6490 ± 273 [arbitrary units (a.u.) ml−1 whole blood, before starting bleeding, and 30762 ± 2650 after bleeding termination (means ± s.e.mean of the values obtained in all experimental groups). All rats treated with saline died within 30 min, their blood levels of free radicals being 35450 ± 5450 a.u. ml−1 blood, 15 min after treatment. Treatment with ACTH‐(1–24) produced a rapid and sustained restoration of arterial pressure, pulse pressure, heart rate and respiratory function, with 100% survival at the end of the observation period (2 h); this was associated with an impressive reduction in the blood levels of free radicals, that were 12807 ± 2995, 10462 ± 2850, 12294 ± 4120, and 10360 ± 2080 a.u. ml−1 blood, 15, 30, 60 and 120 min after ACTH‐(1–24) administration, respectively. These results provide a direct demonstration that (i) in haemorrhagic shock there is a rapid and massive production of highly reactive free radicals, and that (ii) the sustained restoration of cardiovascular and respiratory functions induced by the i.v. injection of ACTH‐(1–24) is associated with a substantial reduction of free radical blood levels. It is suggested that ACTH‐(1–24) prevents the burst of free radical generation during blood mobilisation and subsequent tissue reperfusion, and this may be an important component of its mechanism of action in effectively preventing death for haemorrhagic shock.

Adrenocorticotropin reverses hemorrhagic shock in anesthetized rats through the rapid activation of a vagal anti-inflammatory pathway

“…route, and is mediated by melanocortin MC 4 receptors located in the central nervous system (CNS) [10,13,18]. Such effect is associated with a marked reduction in the plasma levels of inflammatory mediators, such as TNF-a, oxygen free radicals and nitric oxide, and in intercellular adhesion molecule expression by vascular endothelium [2,14,19,20]. This is in agreement with the notion that melanocortins have a peculiar anti-inflammatory activity [7,21].…”

“…ACTH-(1 -24) (160 Ag/kg; Sigma, USA) or saline were injected as i.v. bolus 5 min after bleeding termination, when MAP was stabilized at 20 -25 mm Hg [10,11,[18][19][20]. The dose of ACTH-(1 -24) had proven to be maximally effective in restoring cardiovascular and respiratory functions, and in increasing survival rate, in hemorrhage-shocked rats [27].…”

Melanocortin peptides protect chondrocytes from mechanically induced cartilage injury

“…Protective effects have been demonstrated extensively in murine models of gout [59][60][61] and RA [62]. In addition to these well reported effects in models of arthritis, the melanocortin peptides display a plethora of effects in other disease pathologies For example, in models of cerebral ischemia, -MSH decreased TNF- and IL-1 [85], ACTH-derived peptides have been shown to downgrade nitric oxide [86] and free radicals production [79,87], whilst inducing IL-10 [55] and reducing apoptotic effects [54]. The ability of melanocortins to provoke similar responses in diverse disease models highlights their importance in restoring homeostatic balance to many tissues throughout the entire body.…”

Experimental Models of Hemorrhagic Shock: A Review

“…According to Advanced Trauma Life Support, if the bleeding rate exceeds 40% of circulating blood volume (class IV), the mortality rate is more than 30% in the clinical scenario [19]. Most investigators attempt to recreate this level of shock [12,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49](table 2). …”