Biochemistry of Nitric Oxide Donors: Therapy Vs. Toxicity
A full thickness wound model was used to evaluate the effects of a topically applied polyethyleneimine-based nitric oxide (NO) donor on wound repair involving aged rats. The NO released, for the linear-PEI-NO group, was significant compared to controls (p less than or equal to 0.001) (with a maximal nitrate level of 40 umol on day 1, and an average sustained delivery of 34 umol/day for the remainder of the study. A PBS-wounded control was performed which demonstrated cleaner and faster healing wounds, similar to normal healing, than either of the polymer application groups. For the first time, we report the toxic effects of a polyethyleneimine based compound, as well as, the toxic effects of sustained delivery of excess levels of NO on the wound repair process. Our findings suggest that there exists vague parameters between therapy and toxicity of NO delivery to wounds. Additionally, the effects of transforming growth factor-beta1 (TGF-beta1) on nitric oxide (NO) production and wound repair were evaluated using a mouse perforated-mesentery, connective tissue repair model. A significant decrease in post-wounding urinary nitrate levels (p less than or equal to 0.10) was observed comparing treatment and control groups after the injection of TGF-beta1. Furthermore, TGF-beta1 treated animals showed significant connective tissue repair as compared to controls without an increase in urinary nitrate levels post-wounding. Our findings support an integrated and synergistic relationship between TGF-beta1 and NO in regulating the diverse mechanisms of wound repair. Lastly, nitrosylcobalamin, a vitamin B12-based, non-toxic carrier of nitric oxide (NO), has been synthesized, isolated and characterized in vitro. A UV/VIS analysis was performed confirming the reduction of the cobalt atom of hydroxocobalamin with the binding of NO, causing a shift in the absorption spectra of Co+3 (lambda max 530) to Co+2 (lambda max 500) with the formation of nitrosylcobalamin. The extinction coefficient (emax) of nitrosylcobalamin, as calculated, was 4.8 (mM-1, cm-1). An IR analysis determined the v(NO) vibrational frequency at 1652 cm-1, supporting the binding of NO and suggesting a bent bonding geometry. The cumulative NO release followed first order kinetics and was pH dependent. Nitrosylcobalamin may offer a "drug targeting" approach as a potential, biologically compatible, and selective pharmacological donor compound.
School:The University of Akron
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:nitric oxide nitrosylcobalamin vitamin b12 wound repair apoptosis tgf beta
Date of Publication:01/01/1999