Study of beta endorphin metabolism in inflamed tissue, serum and trypsin solution by liquid chromatography–tandem mass spectrometric analysis

Abstract

Beta endorphin (β-END) is recognised as one of the most significant endogenous neuropeptides, responsible for a wide range of biological activities in the body. However, within the body β-END is exposed to hydrolysis by a variety of enzymes. In this study, we investigated the metabolism and fragmentation pattern of β-END in rat inflamed tissue, in rat serum and in trypsin solution. β-END (1-31)-rat was incubated at 37 °C in each matrix for different incubation times. The resultant fragments were separated using a C4 column and detected by mass spectrometry using total ion current mode. Structural information for the fragments was elucidated using tandem mass spectrometry. Incubation of β-END (1-31)-rat in trypsin solution and in rat serum resulted in 8 and 13 fragments, respectively. Incubation in inflamed rat paw tissue resulted in 22 fragments at pH 7.4 and 26 fragments at pH 5.5. Some of these fragments were common to both pH values. The degradation of β-END (1-31)-rat in inflamed tissue at pH 5.5 was faster than that at pH 7.4. Secondary fragmentation of some larger primary fragments was also observed in this study.

Biotransformation of beta-endorphin and possible therapeutic implications

“…A recent study in our laboratory has identified biotransformation fragments of BE 1–31 in rat inflamed tissue (Herath et al, 2012). This study demonstrated that the hydrolytic metabolism of BE 1–31 in homogenized inflamed tissue was faster than in serum and trypsin incubation; similar results have been noted for the processing of dynorphin (the endogenous ligand for KOR) within inflamed tissue homogenates (Morgan et al, 2012).…”

“…These acidic pH values have been shown to be concordant with those found within inflamed tissue (Dray, 1995). In addition, the nature of the biotransformation hydrolysis was altered, BE 1–31 was shown in inflamed tissue homogenates to be most susceptible for hydrolytic degradation at specific amino acid bonds: (Tyr1-Gly2), (Lys9-Ser10), (Leu17-Phe18-Lys19-Asn20), (Lys24-Asn25), (Lys28-Lys29-Gly30-Gln31) (Herath et al, 2012). This is likely to be a consequence of the inflammatory conditions that affect the enzymes independently and specifically (Lin et al, 2001).…”

Beta-Endorphin 1–31 Biotransformation and cAMP Modulation in Inflammation

“…A recent study in our laboratory has identified biotransformed fragments of BE 1–31 in rat serum, rat inflamed tissue, and following tyrosine hydrolysis in media [24]. This study demonstrated that the hydrolytic metabolism of BE 1–31 in homogenised inflamed tissue was faster than in serum and trypsin incubation.…”

Surface-functionalized cockle shell–based calcium carbonate aragonite polymorph as a drug nanocarrier

“…It is well known that the pH at inflammation site is slightly lower59–61 than the normal physiological pH, which is around 7.4. In this study, we chose PBS whose pH was 6.4 as dissolution medium to investigate the release kinetic of both nanocarrier types simulated at comparable pH of the inflammatory tissues.…”