The effect of C5a and U46619 on the isolated, perfused human placental lobule: development of a method for the online estimation of tissue fluid accumulation

Endothelial indoleamine 2,3-dioxygenase-1 regulates the placental vascular tone and is deficient in intrauterine growth restriction and pre-eclampsia

Indoleamine 2,3-dioxygenase-1 (IDO1) mediates the degradation of L-tryptophan (L-Trp) and is constitutively expressed in the chorionic vascular endothelium of the human placenta with highest levels in the microvasculature. Given that endothelial expression of IDO1 has been shown to regulate vascular tone and blood pressure in mice under the condition of systemic inflammation, we asked whether IDO1 is also involved in the regulation of placental blood flow and if yes, whether this function is potentially impaired in intrauterine growth restriction (IUGR) and pre-eclampsia (PE). In the large arteries of the chorionic plate L-Trp induced relaxation only after upregulation of IDO1 using interferon gamma and tumor necrosis factor alpha. However, ex vivo placental perfusion of pre-constricted cotyledonic vasculature with L-Trp decreases the vessel back pressure without prior IDO1 induction. Further to this finding, IDO1 protein expression and activity is reduced in IUGR and PE when compared to gestational age–matched control tissue. These data suggest that L-Trp catabolism plays a role in the regulation of placental vascular tone, a finding which is potentially linked to placental and fetal growth. In this context our data suggest that IDO1 deficiency is related to the pathogenesis of IUGR and PE.

Arterially perfused eye model of uveitis

OBJECTIVE

To develop an in vitro model of uveitis based on an ex situ perfused eye to evaluate the anti-inflammatory activity of new pharmacological products.

PROCEDURE

Eyes were removed from more than 60 dogs and 9 horses immediately after euthanasia and perfused with nutrient medium through the lateral long ciliary artery. Perfused eyes produced aqueous humour, and perfusion pressure was adjusted to obtain an intraocular pressure in the physiological range. When the eyes were treated with histamine, a complement C5a analogue peptide and hydrogen peroxide, typical signs of uveitis were produced. These included miosis, vascular leakage, reduced intraocular pressure, reduced flow of perfusate and, in some eyes, conjunctival oedema.

RESULTS

Canine eyes showed a decrease in intraocular pressure and a decrease in perfusate flow rate when challenged with 100 mumol/L hydrogen peroxide. Flunixin meglumine (5 mumol/L), ketoprofen (5 mumol/L), indomethacin (5 mumol/L) as well as a new drug pirfenidone (10 mumol/L) prevented changes in intraocular pressure induced by hydrogen peroxide, but did not significantly moderate the mediator-induced changes in perfusate flow.

CONCLUSIONS

This model is suitable for evaluating potential anti-inflammatory activity of drugs without having to induce uveitis in an experimental animal. The technique is suitable for species that range in size from cats to horses.