Physostigmine reverses disturbances of the intestinal microcirculation during experimental endotoxemia

Abstract

Intestinal microcirculatory disturbances play an important role in the pathophysiology of sepsis. A neural antiinflammatory pathway has been suggested as a potential target for therapy that may dampen systemic inflammation. The aim of this study is to investigate the effects of physostigmine, a cholinesterase inhibitor, on the intestinal microcirculation and vascular contractility in experimental endotoxemia. Endotoxemia was induced in Lewis rats by intravenous lipopolysaccharide (LPS) administration. Animals were treated with either physostigmine or saline (control) following LPS challenge. The intestinal microcirculation, including leukocyte-endothelial interaction, functional capillary density (FCD) and non-perfused capillary density (NCD), was examined by intravital microscopy (IVM) 2 hours after LPS administration. The impact of physostigmine on vascular contractility of rat aortic rings was examined by in vitro myography. Physostigmine significantly reduced the number of adhering leukocytes in intestinal submucosal venules (V1 venules: −61%, V3 venules: −36%) of LPS animals. FCD was significantly increased by physostigmine treatment (circular muscle layer: +180%, longitudinal muscle layer: +162%, mucosa: +149%). Low concentrations of physostigmine produced significant contraction of aortic ring preparations, whereas high concentrations produced relaxation. In conclusion, physostigmine treatment significantly improved the intestinal microcirculation in experimental endotoxemia by reducing leukocyte adhesion and increasing FCD.

Therapeutic effects of physostigmine during systemic inflammation

“…Protective effects by PHY have already been described in various experimental models of injury, among others during sepsis/systemic inflammation,15–17 hemorrhagic shock,18–21 and ischemia–reperfusion injury 24–26. However, in all these experimental animal studies, PHY has been administered in a prophylactic manner or early after the injury.…”

“…The benefits of PHY in counteracting harmful actions of sepsis15–17 are primarily attributed to its direct anti-inflammatory capabilities through the so-called cholinergic anti-inflammatory pathway as described by Tracey et al28–30 Cholinesterase inhibition by PHY or its synthetic analog neostigmine has been described to improve survival and inflammation-related organ dysfunction if applied before or directly after the induction of sepsis or systemic inflammation:10,16 Hofer et al demonstrated that both PHY and neostigmine improve survival in a murine CLP model, when treatment started directly after CLP and was continued three times daily for 3 days (single dose: 80 µg/kg) 16. Kalb et al already showed that PHY and neostigmine prevent neuroinflammation in a rat LPS model, when treatment started 5 minutes before the LPS application (single dose: 100 µg/kg) 10.…”

“…Using in vitro experiments on rat aortic rings, Zhou et al demonstrated that lower concentrations of PHY (20–40 µg/kg) produced contraction of rat aortic rings, whereas higher concentrations (70–100 µg/kg) produced relaxation 17. They further found that a recovery from LPS-induced disturbances of the (intestinal) microcirculation by PHY treatment “may be related to its direct effects on blood vessels tension” 17.…”

“…Using in vitro experiments on rat aortic rings, Zhou et al demonstrated that lower concentrations of PHY (20–40 µg/kg) produced contraction of rat aortic rings, whereas higher concentrations (70–100 µg/kg) produced relaxation 17. They further found that a recovery from LPS-induced disturbances of the (intestinal) microcirculation by PHY treatment “may be related to its direct effects on blood vessels tension” 17. Such a dual effect has also been demonstrated for neostigmine – the synthetic analog of PHY:34 Using isolated, spontaneously beating guinea pig, right atrial preparations neostigmine decreased the spontaneously beating rate in a concentration-dependent manner.…”

“…Clinically, PHY is mainly used as an antidote for the treatment of central anticholinergic syndrome in the early postoperative period (eg, delirium)11–13 or is used among other therapeutics to improve hemodynamic and cardiac outputs14 as well as homeostatic imbalances 13. However, various experimental studies of sepsis15–17 and hemorrhagic shock18–21 demonstrated beneficial effects of prophylactical given PHY on macrocirculation, microcirculation, and survival of experimental animals 15–21…”