Background: Nitric oxide (NO) is known to be up-regulated by the induction of induciblenitric oxide synthase (iNOS) in inflammatory conditions. NO gas can be used as a markerof inflammatory activity in hollow organs. In parallel, plasma nitrite + nitrate (NOx) canreflect the ongoing inflammatory activity. We analyzed rectal NO before and after threedays, as well as plasma NOx in patients on glucocorticosteroid (GC) therapy in hospitalizedpatients. The aim of the study was to evaluate the relationship of rectal luminal NO andcirculating plasma NOx in acute fulminant colitis to the outcome as therapeutic responseor colectomy.
Methods: 50 patients with median age 41 (range 20-78) years were hospitalizeddue to acute fulminant colitis and received treatment with high-dose GCs. Luminal nitricoxide was analyzed with chemiluminescence before therapy onset of therapy with GC andon day 3 of treatment. NOx was measured by nitrite/nitrate colorimetric assay. NO levelsand plasma NOx were compared to clinical disease activity index and C-reactive protein(CRP).
Results: 32 responded to GC treatment and 18 did not, resulting in colectomy.The responders had higher luminal NO than non-responders (day 1: 12525±2600, day 3:15590±4157 ppb) vs non-responders (day 1: 2874±1283, day 3: 1137±297 ppb) (p<0.0114).Using an optimal cut-off NO level of 2250 ppb, sensitivity and specificity was 86% and81% for colectomy (p<0.0001). The area under the curve was 0.88 and likelihood ratio4.8. Similarly, plasma NOx was higher in responders vs non-responders (day 1: 6.2±0.3 vs3.9±0.4 umol/L) (p<0.0001). Using plasma NOx, we found a corresponding cut-off at 5umol/L with sensitivity 87% and specificity 87%. The area under the curve was 0.88 andlikelihood ratio 6.7. Luminal NO was also correlated to plasma NOx (r=0.33, p=0.0205).In the responder group, CRP levels decreased (day 1: 22.31±2.95, day 3: 15.69±3.57mg/L), whereas among non-responders CRP levels increased (day 1: 45.83±11.10, day 3:76.35±16.96 mg/L) (p<0.0167). Kaplan-Meier analysis showed that patients with baselineNO levels lower than 2250 ppb were at a significantly higher risk of colectomy within onemonth from onset of GCS treatment (p<0.0001). Twelve out of 18 (67%) in patients withday 1 NO <2250 ppb were colectomized, the corresponding number of patients with NO>2250 ppb was 3 out of 32 (9%). In a similar manner, using plasma NOx <5 uml/L foranalysis, we found 13 (72%) to be colectomized, and with >5 umol/L only two (6%).
Conclusion: NO and its oxidation product NOx are markers of inflammatory activity in thegut. However, with more intense inflammation and mucosal damage, the less NO is produced.Luminal NO as well as plasma NOx can be used as a sensitive biomarker to predict colectomyin the outcome of acute fulminant colitis
Uppsala, 2015. Vol. 148