To determine the effects of ultraviolet light, natural light and ionizing radiation on pyridinium cross‐links in bone and urine using high‐performance liquid chromatography

Abstract

The aims of the study were to characterize the denaturation of urinary free and conjugated pyridinoline (Pyr) and deoxypyridinoline (Dpyr) on exposure to ultraviolet (UV) and natural light at different pH levels and to study the effects of X- and gamma-irradiation on Pyr and Dpyr in urine and in the mineralized and non-mineralized compartments of human bone. Urine samples from six normal subjects, adjusted to pH 3.0, 7.0 and 9.0 were exposed to UV light for up to 3 days. Urine collections (2 mL and 24 h) from three subjects, pH adjusted to 1.0, 2.0, 3.0, 4.0 and 5.0, were exposed to natural light for up to 1 day. Urine samples and bone slices from seven human cadaveric femurs were irradiated with increasing doses of X-rays (0-100 Gy) and high-dose gamma-radiation (28 kGy). Mineralized and non-mineralized bone were separated using a modification of a published method employing heat denaturation followed by trypsin hydrolysis and analysed for Pyr, Dpyr and hydroxyproline (Hypro). The rate of UV photolysis of urinary Pyr and Dpyr increased with pH and was faster in the free fraction (after 3 days' exposure: free Pyr and Dpyr at pH 7.0 vs. 9.0, P < 0.05, conjugated pH 3.0 vs. 9.0, P < 0.05). Exposure to natural light for 3 h did not significantly decrease urinary Pyr and Dpyr in either sample collections, but levels were reduced in the 2-mL aliquots after exposure for 1 day (P < 0.05). X-irradiation of urine and bone did not affect Pyr and Dpyr. Pyr content was similar in both bone compartments (Pyr/ Hypro = 0.12 +/- 0.004), but Dpyr was higher in the non-mineralized compartment (Dpyr/Hypro = 0.047 +/- 0.002 vs. 0.038 +/- 0.002, P < 0.001). UV light and gamma-irradiation result in denaturation of pyridinium cross-links in urine. These cross-links are present in both the mineralized and non-mineralized bone compartments but are not affected by the doses of gamma-irradiation that denature these cross-links in urine.

On the effect of X-ray irradiation on the deformation and fracture behavior of human cortical bone

“…We have previously observed increases in the amide I peak with dehydration and increasing age and have attributed them to broadening of the resonance profile for the amide   * transition caused by changes in the intrafibrallar environment of the collagen molecules [49,50]. Here, we believe that the increase is due to increased collagen cross-linking induced by the radiation damage, as similarly reported for gamma radiation studies [15][16][17]. Finally, we note that at a dose of 630 kGy, the spectral features were broadened to an extent such that the individual peaks could not be observed.…”

“…It is well documented that this can be severely affected by radiation. In particular, the majority of damage from gamma radiation is induced in bone by the radiolysis of water molecules which generate free radicals which in turn target bonds within the collagen structure [62,63], resulting in cross-linking reactions in the collagen molecules [15][16][17].…”

“…However, gamma irradiation is also known to adversely affect the mechanical and biological properties of tissue in a dose-dependent manner by degrading the collagen [6][7][8][9][10][11][12][13][14]. Specifically, gamma rays split polypeptide chains; in wet specimens, irradiation causes release of free radicals via radiolysis of water molecules that induces cross-linking reactions in collagen molecules [15][16][17].…”

Sterilization of allograft bone: effects of gamma irradiation on allograft biology and biomechanics

“…The tissue damage caused by gamma radiation occurs through two mechanisms Colwell et al 1996;Dziedzic-Goclawska et al 2005;Hamer et al 1999). In the dry state, splitting of polypeptide chains occurs under the direct influence of gamma rays (Dziedzic- Goclawska et al 2005).…”

Effects of high-dose gamma irradiation on tensile properties of human cortical bone: Comparison of different radioprotective treatment methods

“…The studies on detrimental effects of gamma sterilization on elastic and plastic properties of the bone have demonstrated that decreased cross-linking of the collagen (Cheung et al, 1990;Bailey, 1967;Salehpour et al, 1995;Akkus et al, 2005;Ward, 1990;Wang et al, 2001;Colwell et al, 1996) significantly affects the mechanical properties of the bone within the plastic region (Akkus et al, 2005;Currey et al, 1997;Hamer et al, 1996) and results in ductility reduction, while elastic properties remain almost unaffected (Akkus et al, 2005;Currey et al, 1997). For instance, the reduction of the post-yield strength (by 70-87%) and decrease of the fatigue strength (by 87%) of the femoral cortical bone exposed to 36.4 kGy have been reported (Akkus et al, 2005;Currey et al, 1997).…”