Wound collagen deposition in rats: effects of an NO-NSAID and a selective COX-2 inhibitor

Abstract

Selective cyclo-oxygenase (COX)-2 inhibitors and nitric oxide-releasing nonsteroidal anti-inflammatory drugs (NSAIDs) exhibit reduced toxicity in the gastrointestinal tract, but may affect wound healing in other tissues. In this study, we have compared the effects of a selective COX-2 inhibitor (celecoxib), a nitric-oxide releasing derivative of naproxen (HCT-3012) and naproxen in a model of wound collagen deposition in the rat. Polyvinyl alcohol sponges were implanted subcutaneously in rats. The rats were treated daily for 5 days with the test drugs at equieffective anti-inflammatory doses. Naproxen (10 mg kg(-1)) significantly decreased (45%) collagen deposition at the wound site relative to the vehicle-treated control group. In contrast, HCT-3012 (14.5 mg kg(-1)) significantly increased (62%) collagen deposition, while celecoxib (10 mg kg(-1)) had no effect. Naproxen and HCT-3012 suppressed prostaglandin (PG) E(2) levels at the wound site and whole blood thromboxane synthesis to similar degrees. Celecoxib had no significant effect on wound fluid PGE(2) levels, but slightly reduced whole blood thromboxane synthesis (by 17%). COX-1 mRNA and protein were expressed in the wound exudate, the skin surrounding the wound and in normal skin. In contrast, COX-2 mRNA, but not protein, was expressed in wound and normal skin. These results demonstrate that HCT-3012 can significantly enhance collagen deposition at a wound site, despite inhibiting prostaglandin synthesis to the same extent as the parent drug. Nitric oxide-releasing NSAIDs may represent a safer alternative to standard NSAIDs for use as anti-inflammatory and analgesic agents by post-surgery patients.

Figure 1

Inhibition of inflammatory prostaglandin E₂ synthesis in the carrageenan-airpouch model by naproxen (10 mg kg⁻¹), HCT-3012 (14.5 mg kg⁻¹) and celecoxib (10 mg kg⁻¹). ^**P<0.01 versus the vehicle-treated group.

Figure 2

Hydroxyproline content in polyvinyl alcohol sponges harvested 5 days after subcutaneous implantation (2 h after the final dose of the test drug or vehicle). ^*P<0.05, ^**P<0.01 vs the control (vehicle-treated) group. δδδP<0.001 versus the naproxen-treated group.

Figure 3

Prostaglandin E₂ concentrations in wound fluid samples obtained 5 days after implantation of polyvinyl alcohol sponges (2 h after the final dose of the test drug or vehicle). ^*P<0.05, ^**P<0.01 versus the control (vehicle-treated) group.

Figure 4

Whole blood thromboxane B₂ synthesis in rats treated for 5 days with vehicle, naproxen, HCT-3012 or celecoxib. The blood samples were taken 2 h after the final dose of the test drug or vehicle. ^***P<0.001 versus the control (vehicle-treated) group.

Figure 5

Nitrite (NO₂⁻) and nitrate (NO₃⁻) concentrations in wound fluid samples obtained 5 days after subcutaneous implantation of polyvinyl alcohol sponges (2 h after the final dose of the test drug or vehicle). ^*P<0.05 versus the control (vehicle-treated) group.

Figure 6

Western blots for COX-1 and COX-2 obtained from wound exudate cell pellet lysates (lanes 1–5; 20 μg protein). Lane 6: COX-2 positive control (LPS-activated macrophage lysate; 2 μg protein).