Endothelium-dependent vasodilation in response to Pseudomonas aeruginosa lipopolysaccharide: an in vitro study on canine arteries

Abstract

Early systemic arterial hypotension is a common clinical feature of Pseudomonas septicemia. To determine if Pseudomonas aeruginosa endotoxin induces the release of endothelium-derived nitric oxide (EDNO), an endogenous nitrovasodilator, segments of canine femoral, renal, hepatic, superior mesenteric, and left circumflex coronary arteries were suspended in organ chambers (physiological salt solution, 95% O 2 /5% CO 2 , pH 7.4, 37 o C) to measure isometric force. In arterial segments contracted with 2 µM prostaglandin F 2α , Pseudomonas endotoxin (lipopolysaccharide (LPS) serotype 10(Habs) from Pseudomonas aeruginosa (0.05 to 0.50 mg/ml)) induced concentration-dependent relaxation of segments with endothelium (P<0.05) but no significant change in tension of arteries without endothelium. Endothelium-dependent relaxation in response to Pseudomonas LPS occurred in the presence of 1 µM indomethacin, but could be blocked in the coronary artery with 10 µM N G -monomethyl-L-arginine (L-NMMA), a competitive inhibitor of nitric oxide synthesis from Larginine. The inhibitory effect of L-NMMA on LPS-mediated vasorelaxation of the coronary artery could be reversed by exogenous 100 µM L-arginine but not by 100 µM D-arginine. These experiments indicate that Pseudomonas endotoxin induces synthesis of nitric oxide from L-arginine by the vascular endothelium. LPS-mediated production of EDNO by the endothelium, possibly through the action of constitutive nitric oxide synthase (NOSc), may decrease systemic vascular resistance and may be the mechanism of early hypotension characteristic of Pseudomonas septicemia.

Aflatoxin B 1 degradation by liquid cultures and lysates of three bacterial strains

“…Furthermore, some bacterial cultures are not only toxic, but also possesses the ability to release endotoxins after lysis as the case may be for fungi in producing mycotoxins, which could result in higher cytotoxicity compared to the parent AFB 1 molecule. Reports have documented endotoxin production from the bacterial species utilized in this study (Bjork et al, 1992;Evora et al, 1998;Nya and Austin, 2010;Williams, 2007;Zodrovenko et al, 1990), thus necessitating the investigation of the potential GRAS status of these strains. Percentage cell viability after exposure to the bacterial cultures and lysates is presented in Fig.…”

Effects ofPseudomonas aeruginosaendotoxin on vasodilation in the intact spinotrapezius muscle

“…In preliminary studies, we determined that repeated suffusions of L-NAME and D-NAME (each, 10.0 M) for 90 min had no significant effects on arteriolar diameter (1 Ϯ 2 and 1 Ϯ 1% for L-NAME and 1 Ϯ 1 and 1 Ϯ 1% for D-NAME). The concentrations of L-NAME and D-NAME used in these studies are based on previous studies in our laboratory and reports in the literature (1,12,16,23,25,36,40,42,45,47). The former has been shown to attenuate NO-dependent vasodilation in the in situ peripheral microcirculation of hamsters (23,40).…”

“…Effects of P. aeruginosa LPS on acetylcholine-and nitroglycerin-induced vasodilation. The purpose of these studies was to determine whether P. aeruginosa LPS modulates vascular smooth muscle responsiveness to endogenous and exogenous NO in the in situ spinotrapezius muscle (1,12,16,28,48). After the equilibration period, acetylcholine (10.0 M), a receptor-and endothelium-dependent vasodilator, or nitroglycerin (10.0 M), an NO donor that elicits endothelium-independent vasodilation, was suffused for 7 min.…”

“…To this end, Pseudomonas aeruginosa is an important opportunistic gram-negative bacterium often associated with sepsis syndrome and poor outcome, particularly among patients with impaired immune responses and hospitalized patients (3,5,6,31). P. aeruginosa sepsis syndrome is characterized by profound vasodilation in skeletal muscles, which harbor the largest proportion of resistance arterioles in the peripheral circulation (4,8,13,22,29,32,38,48), that leads to intractable hypotension (1,2,9,12,28). A growing body of experimental evidence suggests that P. aeruginosa lipopolysaccharide (LPS), a macromolecular glycolipid component of bacterial wall (11,18,35), plays an important role in the pathophysiology of this response (2,9,11,12,18).…”

“…P. aeruginosa sepsis syndrome is characterized by profound vasodilation in skeletal muscles, which harbor the largest proportion of resistance arterioles in the peripheral circulation (4,8,13,22,29,32,38,48), that leads to intractable hypotension (1,2,9,12,28). A growing body of experimental evidence suggests that P. aeruginosa lipopolysaccharide (LPS), a macromolecular glycolipid component of bacterial wall (11,18,35), plays an important role in the pathophysiology of this response (2,9,11,12,18). However, the mechanisms underlying the deleterious effects of clinically relevant concentrations of P. aeruginosa LPS on resistance arterioles in skeletal muscles in vivo are uncertain (10,21,32,35,41).…”