Ischemia/reperfusion (IR) injury is a leading cause of acute renal failure and an important contributor to allograft damage. Tissue factor (TF) is up-regulated during IR, and TF inhibition reduces renal injury. However, the underlying mechanisms by which TF contributes to injury have not been elucidated. We postulated that TF contributes to IR injury by production of coagulation proteases and subsequent signaling by protease activated receptor (PARs). We compared renal injury after 25 minutes of bilateral renal ischemia and varying periods of reperfusion in C57BL/6 mice, those expressing low levels of TF (low-TF), hirudin-treated C57BL/6, and mice lacking either PAR-1 or PAR-2. C57BL/6 mice developed severe renal failure and died within 48 hours of reperfusion. In contrast, low-TF, hirudin-treated C57BL/6, and PAR-1-/- mice were protected from renal failure and had reduced mortality, tubular injury, neutrophil accumulation, and lower levels of the chemokines KC and MIP-2. Importantly, PAR-1-/- mice had lower chemokine levels despite up-regulation of TF and fibrin deposition. In addition, treating PAR-1-/- mice with hirudin conferred no additional benefit. Somewhat surprisingly, PAR-2 deficiency did not protect from renal failure. These experiments indicate that increased TF activity after renal IR leads to increased CXC chemokine expression and subsequent neutrophil-mediated injury predominantly by thrombin-dependent PAR-1 signaling.

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Background: Therapeutic drug monitoring of tumor necrosis factor inhibitors, such as adalimumab (ADM), is increasingly being performed for the management of autoimmune diseases. However, there can be significant variation in drug and antibody concentrations obtained by different assay methods. The aim of this study was to compare the performance of 4 enzyme-linked immunosorbent assay (ELISA) kits for measuring ADM and anti-ADM antibodies. Method: Dilutions of ADM or anti-ADM spiked sera were assessed for recovery rate and precision using the following 4 kits: LISA-Tracker (Theradiag, Croissy-Beaubourg, France), Promonitor (Grifols, Barcelona, Spain), Ridascreen (R-Biopharm, Darmstadt, Germany), and Shikari (Matriks Biotek, Gölbaşi/Ankara Turkey). Interference samples were also assessed. Results: At the therapeutic concentration, ADM detection was comparable among the 4 ELISA kits. Lisa-Tracker and Shikari kits produced low-range false positive results in normal sera. Infliximab and etanercept caused false positives in Lisa-Tracker and Shikari kits. Anti-ADM antibody ELISA kits performed differently with spiked samples because of different measuring units and ranges. Ridascreen and Shikari kits were dose responsive across the entire standard curve and correlated well with each other (r2 = 0.997). Cross reactivity was observed in rheumatoid factor positive sera tested on the Promonitor anti-ADM kit. Conclusions: All ADM kits tested were dose responsive within the therapeutic range and correlated well. The significance of observed low-range false positives and cross reactivity with infliximab in LISA-Tracker and Shikari kits is dependent on the indications received for testing in the laboratory. Anti-ADM ELISA kits produced varied results for spiked sera; however, they showed good precision. Inter-kit variability suggested that anti-ADM levels should be compared only when using the same method.

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Background The optimal infliximab dose intensification strategy to address secondary loss of response (LOR) remains unclear. This study aimed to compare clinical and pharmacokinetic outcomes following (i) upfront infliximab re‐induction with (ii) ongoing 6‐weekly dose interval shortening (DIS), after the same number of doses. Methods A prospective parallel cohort study of inflammatory bowel disease patients who required infliximab dose intensification for secondary LOR using (i) re‐induction (i.e., repeat 5 mg/kg 0, 2, 6‐week dosing) followed by 8‐weekly maintenance or (ii) 6‐weekly 5 mg/kg DIS was undertaken. Week 32 clinical response was the primary outcome, with secondary evaluation of infliximab pharmacokinetics and predictors of response. Results Of 104 patients, 54 underwent re‐induction, and 50 underwent 6‐weekly DIS; 43 per cohort had clinically active disease, with comparable baseline infliximab levels (2.03 vs 2.02 ug/mL, P = 0.83). Clinical response was similar across re‐induction and DIS cohorts at weeks 12 (69.8 vs 65.1%) and 32 (53.5 vs 62.8%, each P > 0.50); however, both strategies demonstrated distinct pharmacokinetic profiles at weeks 6 (18.45 vs 5.36 ug/mL, P < 0.01), 12 (8.94 vs 5.96 ug/mL, P = 0.02) and 30 (3.89 vs 6.35 ug/mL, P = .0.02). In multivariable analyses, objectively verified active disease at baseline (OR 12.92, 95% CI [1.84–90.84], P = 0.01), subtherapeutic week 6 infliximab levels (OR 0.12, 95% CI [0.01, 0.99], P = 0.049) and week 12 clinical response (OR 5.44, 95% CI [1.20–19.97], P = 0.04) were associated with week 32 response, as were week 2 infliximab levels (OR 1.34, 95% CI [1.02–1.47], P = 0.04) following re‐induction. Following re‐induction, week 2 infliximab levels <15.6 ug/mL (AUROC 0.76, 95% CI [0.54–0.99], P < 0.05) predicted nonresponse at week 32. Conclusion Dose intensification strategy impacted immediate and sustained infliximab levels but not clinical response. Upfront intensification was associated with short‐term pharmacokinetic advantages, including predictors of response, that diminished with time. Hence, when applying upfront dose intensification, clinicians should consider continuing intensified dosing to sustain early pharmacokinetic advantages based on predictors of (non)response.

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