Delayed addition of dexamethasone suppresses chemokine mRNA during ongoing inflammation

This study aimed to examine the effects of delayed therapy on the inflammatory response. Heparinized whole blood was collected, stimulated with 50ng/ml LPS, incubated at 37°C with 5% CO 2 and continuous rotation. Results showed peak protein levels of the pro‐inflammatory cytokines TNF (1.8 ± 0.38 (3h)), IL‐6 (62.6 ± 8.9), and IL‐1β 5.3 ± 1.7) by 3–6 hours post‐stimulation, while chemokine (CXCL1 from 1.8 ± 0.72 to 10.9 ± 4.6; CXCL8 from 4.9 ± 1.4 to 18.0±4.6*) levels rose over 24 hours. Published data suggest that cytokines signal through a common pathway via NF‐κB transcription factors, however the present data suggest possible differential regulation. To investigate this possibility, dexamethasone (dex; 10 −6 M) was added to the system 6 hours post‐LPS, and its effect on protein kinetics assayed. Delayed dex had little effect on cytokines, but significantly suppressed chemokine protein levels (CXCL1 6.3 ± 1.5; CXCL8 4.3 ± 1.8*). To determine the level of regulation, the effects of delayed dex on mRNA kinetics was assessed. Delayed dex noticeably, but insignificantly, suppressed chemokine mRNA (CXCL1 from 2.8 ± 1.1 to 0.80 ± 0.59 and CXCL8 from 90.7 ± 55.3 to 47.8 ± 20.6), further implying a difference in regulation of cytokine and chemokine expression during ongoing inflammation. While additional experimentation is necessary, these preliminary data are key to understanding the regulating ongoing inflammation.