High-performance liquid chromatographic analysis of a selective cyclooxygenase-1 inhibitor SC-560 in rat serum: application to pharmacokinetic studies

Inhibition of cyclooxygenase-2 prevents adverse effects induced by phosphodiesterase type 4 inhibitors in rats

BACKGROUND AND PURPOSE

Phosphodiesterase type 4 (PDE4) inhibitors such as roflumilast are currently being developed as anti-inflammatory treatments for chronic airway disorders. However, high doses of PDE4 inhibitors have also been linked to several side effects in different animal species, including pro-inflammatory effects in the rat. Here, we analysed PDE4-related toxicological findings in a rat model and how these side effects might be therapeutically prevented.

EXPERIMENTAL APPROACH

Wistar rats were treated orally once daily with 10 mg·kg⁻¹ roflumilast for 4 days. Macroscopic changes were monitored throughout the study and further parameters were analysed at the end of the experiment on day 5. In addition, the effects of concomitant treatment with cyclooxygenase (COX) inhibitors were assessed.

KEY RESULTS

Supratherapeutical treatment with roflumilast induced marked body and spleen weight loss, diarrhea, increased secretory activity of the harderian glands, leukocytosis, increased serum cytokine-induced neutrophil chemoattractant-1 (CINC-1) levels, and histopathological changes in thymus, spleen, mesentery and mesenteric lymph nodes. All these toxicological findings could be prevented by the non-steroidal anti-inflammatory drug (NSAID) and non-selective COX inhibitor, diclofenac, given orally. Similar protective effects could be achieved by the COX-2 selective inhibitor lumiracoxib, whereas the COX-1 selective inhibitor SC-560 was generally not effective.

CONCLUSIONS AND IMPLICATIONS

Treatment with an NSAID inhibiting COX-2 prevents the major effects found after subchronic overdosing with the PDE4-specific inhibitor roflumilast. If this effect translates into humans, such combined treatment may increase the therapeutic window of PDE4 inhibitors, currently under clinical development.

Modifications produced by selective inhibitors of cyclooxygenase and ultra low dose aspirin on platelet activity in portal hypertension

AIM: To study the mechanism involved in the potentially beneficial effect of ultra low dose aspirin (ULDA) in prehepatic portal hypertension, rats were pretreated with selective COX 1 or 2 inhibitors (SC-560 or NS-398 respectively), and subsequently injected with ULDA or placebo.

METHODS: Portal hypertension was induced by portal vein ligation. Platelet activity was investigated with an in vivo model of laser induced thrombus production in mesenteric circulation and induced hemorrhagic time (IHT). Platelet aggregation induced by ADP and dosing of prostanoid products 6-keto-PGF_1α, TXB₂, PGE₂ and LTB₄ were also performed.

RESULTS: The portal hypertensive group receiving a placebo showed a decreased in vivo platelet activity with prolonged IHT, an effect that was normalized by ULDA. SC-560 induced a mild antithrombotic effect in the normal rats, and an unmodified effect of ULDA. NS-398 had a mild prothrombotic action in portal hypertensive rats, similar to ULDA, but inhibited a further effect when ULDA was added. An increased 6-keto-PGF_1α was observed in portal hypertensive group that was normalised after ULDA administration. TXA₂ level after ULDA, remained unchanged.

CONCLUSION: These results suggest that the effect of ULDA on platelet activity in portal hypertensive rats, could act through a COX 2 pathway more than the COX 1, predominant for aspirin at higher doses.