Determination of hydroxyproline in plasma and tissue using electrospray mass spectrometry

Analysis of Hydroxyproline in Collagen Hydrolysates

Hydroxyproline (Hyp) is an imino acid posttranslationally formed by sequence-specific hydroxylases in the repeating collagen Gly-Xaa-Yaa triad present in all collagen types of all species. In both Xaa- and Yaa-positions, Pro is the most common residue, often oxidized to 4-Hyp in the Yaa- and rarely to 3-Hyp in the Xaa-positions. Here we describe the qualitative and quantitative analysis of 3- and 4-Hyp-isomers by separating the free imino acids either with hydrophilic interaction chromatography (HILIC) or after derivatization with reversed-phase chromatography (RPC). In both cases the compounds were detected by electrospray-ionization mass spectrometry.

Bioanalytical Method for the Determination of Hydroxyproline in Mouse Kidney by High-Performance Liquid Chromatography with Tandem Mass Spectrometric Detection

An analytical method was developed and validated for the measurement of hydroxyproline (Hyp) levels in mouse kidney by high-performance liquid chromatography with tandem mass spectrometric detection (LC/MS/MS) using an analytical column specially designed for the LC/MS/MS analysis for intact amino acids. Tissue hydrolyzed with hydrochloric acid could be directly injected into the LC/MS/MS, as well as separated and detected using the deuterium labelled Hyp as an internal standard. The calibration curve showed good linearity from 5 to 500 nmol/mg of tissue; the precision and accuracy, including within- and between-run, were less than 6% and within 100 ± 6%, respectively.

Antifibrotic effect of AT-1 blocker and statin in rats with hepatic fibrosis

Hepatic fibrosis is an outcome of chronic liver injury. Angiotensin II (ANG II) may play a role in the pathogenesis of hepatic fibrosis. Certain drugs such as ACE inhibitors, ANG II antagonists, and even statins could interfere with the renin angiotensin system and modulate its deleterious effects. This study was carried out to investigate the possible role of losartan and atorvastatin in liver fibrosis. Liver fibrosis was induced in rats by i.p. injection of 50% CCl₄ twice per week for 8 weeks. The rats intoxicated with CCl₄ were divided into four groups: fibrosis control; losartan group; atorvastatin group; and co-treated group. A fifth group of normal healthy rats served as a control group. The results showed that losartan and atorvastatin, either alone or in combination, significantly decreased ALT, AST, hyaluronic acid and hydroxyproline levels in their groups compared to those of the fibrosis control group. A significant decrease in TGF-β was found in the losartan and co-treated groups but not in the atorvastatin group. These biochemical data were supported by liver histopathology and α-SMA. The results indicate that the combined treatment with both losartan and atorvastatin produced a greater effect than either drug alone and proved a beneficial role in inhibiting or reversing liver fibrosis.

Inhibition of soluble epoxide hydrolase attenuates hepatic fibrosis and endoplasmic reticulum stress induced by carbon tetrachloride in mice

Liver fibrosis is a pathological condition in which chronic inflammation and changes to the extracellular matrix lead to alterations in hepatic tissue architecture and functional degradation of the liver. Inhibitors of the enzyme soluble epoxide hydrolase (sEH) reduce fibrosis in the heart, pancreas and kidney in several disease models. In this study, we assess the effect of sEH inhibition on the development of fibrosis in a carbon tetrachloride (CCl4)-induced mouse model by monitoring changes in the inflammatory response, matrix remolding and endoplasmic reticulum stress. The sEH inhibitor 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) was administered in drinking water. Collagen deposition in the liver was increased five-fold in the CCl4-treated group, and this was returned to control levels by TPPU treatment. Hepatic expression of Col1a2 and 3a1 mRNA was increased over fifteen-fold in the CCl4-treated group relative to the Control group, and this increase was reduced by 50% by TPPU treatment. Endoplasmic reticulum (ER) stress observed in the livers of CCl4-treated animals was attenuated by TPPU treatment. In order to support the hypothesis that TPPU is acting to reduce the hepatic fibrosis and ER stress through its action as a sEH inhibitor we used a second sEH inhibitor, trans-4-{4-[3-(4-trifluoromethoxy-phenyl)-ureido]-cyclohexyloxy}-benzoic acid (t-TUCB), and sEH null mice. Taken together, these data indicate that the sEH may play an important role in the development of hepatic fibrosis induced by CCl4, presumably by reducing endogenous fatty acid epoxide chemical mediators acting to reduce ER stress.

Quantitative evaluation of collagen crosslinks and corresponding tensile mechanical properties in mouse cervical tissue during normal pregnancy

The changes in the mechanical integrity of the cervix during pregnancy have implications for a successful delivery. Cervical collagens are known to remodel extensively in mice with progressing gestation leading to a soft cervix at term. During this process, mature crosslinked collagens are hypothesized to be replaced with immature less crosslinked collagens to facilitate cervical softening and ripening. To determine the mechanical role of collagen crosslinks during normal mouse cervical remodeling, tensile load-to-break tests were conducted for the following time points: nonpregnant (NP), gestation day (d) 6, 12, 15, 18 and 24 hr postpartum (PP) of the 19-day gestation period. Immature crosslinks (HLNL and DHLNL) and mature crosslinks (DPD and PYD) were measured using ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). There were no significant changes in the total immature crosslink density (HLNL+DHLNL mol per collagen mol) throughout normal mouse gestation (range: 0.31-0.49). Total mature crosslink density (PYD+DPD mol per collagen mol) decreased significantly in early softening from d6 to d15 (d6: 0.17, d12: 0.097, d15: 0.026) and did not decrease with further gestation. The maturity ratio (total mature to total immature crosslinks) significantly decreased in early softening from d6 to d15 (d6: 0.2, d15: 0.074). All of the measured crosslinks correlated significantly with a measure of tissue stiffness and strength, with the exception of the immature crosslink HLNL. This data provides quantitative evidence to support the hypothesis that as mature crosslinked collagens decline, they are replaced by immature collagens to facilitate increased tissue compliance in the early softening period from d6 to d15.

LC-MS metabolomics of psoriasis patients reveals disease severity-dependent increases in circulating amino acids that are ameliorated by anti-TNFα treatment

Psoriasis is an immune-mediated highly heterogeneous skin disease in which genetic as well as environmental factors play important roles. In spite of the local manifestations of the disease, psoriasis may progress to affect organs deeper than the skin. These effects are documented by epidemiological studies, but they are not yet mechanistically understood. In order to provide insight into the systemic effects of psoriasis, we performed a nontargeted high-resolution LC–MS metabolomics analysis to measure plasma metabolites from individuals with mild or severe psoriasis as well as healthy controls. Additionally, the effects of the anti-TNFα drug Etanercept on metabolic profiles were investigated in patients with severe psoriasis. Our analyses identified significant psoriasis-associated perturbations in three metabolic pathways: (1) arginine and proline, (2) glycine, serine and threonine, and (3) alanine, aspartate, and glutamate. Etanercept treatment reversed the majority of psoriasis-associated trends in circulating metabolites, shifting the metabolic phenotypes of severe psoriasis toward that of healthy controls. Circulating metabolite levels pre- and post-Etanercept treatment correlated with psoriasis area and severity index (PASI) clinical scoring (R² = 0.80; p < 0.0001). Although the responsible mechanism(s) are unclear, these results suggest that psoriasis severity-associated metabolic perturbations may stem from increased demand for collagen synthesis and keratinocyte hyperproliferation or potentially the incidence of cachexia. Data suggest that levels of circulating amino acids are useful for monitoring both the severity of disease as well as therapeutic response to anti-TNFα treatment.

Slaughtering age effect on carcass traits and meat quality of italian heavy draught horse foals

The present work describes the effect of slaughtering age on horse carcass traits and on meat quality. Eighteen male Italian heavy draught horse (IHDH) breed foals were employed in the study. Soon after foaling they were randomly subdivided in 3 groups according to 3 age at slaughtering classes: 6 months old, 11 months old and 18 months old. Live weight, hot carcass weight and dressing percentage of each animal were recorded. After slaughtering, meat samples were collected from Longissimus Dorsi muscle between 13th and 18th thoracic vertebra of each animal and then analyzed. The right half carcass of each animal was then divided in cuts. Each one was subdivided into lean, fat and bones. Then, the classification of the lean meat in first and second quality cuts was performed according to the butchers' customs. Older animals were characterized by a lower incidence of first quality cuts (p<0.01) on carcass. Younger animals showed greater content in protein (p<0.01). Fatty acid profile showed an increasing trend of PUFA connected to the increasing of slaughtering age (p<0.05). The unsaturation index of intramuscular fatty acids was not affected by slaughtering age, confirming that horse meat, if compared to beef, is more suitable from a nutritional point of view. Season influenced reproduction, birth as well as production aspects of this species. The different slaughtering age could represent the way to produce meat of IHDH foals during the entire year without change in the qualitative standard expected by consumers.

Effect of nutritive level on carcass traits and meat quality of IHDH foals

The present work describes the effect of nutritive level on horse carcass traits and on meat quality. Eighteen male Italian Heavy Draught Horse (IHDH) breed foals were employed in the study. Soon after foaling they were randomly subdivided into three groups according to three nutritive level classes: 150%, 180% and 200% of maintenance requirements. Live weight, hot carcass weight and dressing percentage of each animal were recorded. After slaughtering, meat samples were collected from Longissimus dorsi muscle. The right half carcass of each animal was then divided into cuts. Each one was subdivided into lean, fat and bones. Live weight, carcass weight and dressing percentage were not affected by nutritive level (P > 0.05). Horses fed with the lower nutritive level showed a higher incidence of lean and a lower incidence of fat (P < 0.01). Moreover, fatty acid profile was not affected by nutritive level (P > 0.05). Probably the tendency of IHDH foals to concentrate adipogenesis in the subcutaneous district could explain the lack of influence of nutritive level on meat quality parameters and its influence on carcass and cut composition, which tend to be richer in fat.

Lysyl oxidase-mediated collagen crosslinks may be assessed as markers of functional properties of tendon tissue formation

Mechanical property elaboration of engineered tissues is often assumed on the basis of gene and protein characterizations, rather than mechanical testing. However, we recently demonstrated that mechanical properties are not consistently correlated with matrix content and organization during embryonic tissue development. Based on this, mechanical properties should be assessed independently during natural or engineered tissue formation. Unfortunately, mechanical testing is destructive, and thus alternative means of assessing these properties are desirable. In this study, we examined lysyl oxidase (LOX)-mediated crosslinks as markers for mechanical properties during embryonic tendon formation and the potential to detect them non-destructively. We used tandem mass spectrometry (LC-MS/MS) to quantify changes in hydroxylysyl pyridinoline (HP) and lysyl pyridinoline (LP) crosslink density in embryonic chick tendon as a function of developmental stage. In addition, we assessed a multiphoton imaging approach that exploits the natural fluorescence of HP and LP. With both techniques, we quantified crosslink density in normal and LOX-inhibited tendons, and correlated measurements with mechanical properties. HP and LP crosslink density varied as a function of developmental stage, with HP-to-dry mass ratio correlating highly to elastic modulus, even when enzymatic crosslink formation was inhibited. Multiphoton optical imaging corroborated LC-MS/MS data, identifying significant reductions in crosslink density from LOX inhibition. Taken together, crosslink density may be useful as a marker of tissue mechanical properties that could be assessed with imaging non-destructively and perhaps non-invasively. These outcomes could have significant scientific and clinical implications, enabling continuous and long-term monitoring of mechanical properties of collagen-crosslinked tissues or engineered constructs.

Cervical collagen network remodeling in normal pregnancy and disrupted parturition in Antxr2 deficient mice

The remodeling of the cervix from a rigid barrier into a compliant structure, which dilates to allow for delivery, is a critical process for a successful pregnancy. Changes in the mechanical properties of cervical tissue during remodeling are hypothesized to be related to the types of collagen crosslinks within the tissue. To further understand normal and abnormal cervical remodeling, we quantify the material properties and collagen crosslink density of cervical tissue throughout pregnancy from normal wild-type and Anthrax Toxin Receptor 2 knockout (Antxr2-/-) mice. Antxr2-/- females are known to have a parturition defect, in part, due to an excessive accumulation of extracellular matrix proteins in the cervix, particularly collagen. In this study, we determined the mechanical properties in gestation-timed cervical samples by osmotic loading and measured the density of mature collagen crosslink, pyridinoline (PYD), by liquid chromatography tandem mass spectrometry (LC-MSMS). The equilibrium material response of the tissue to loading was investigated using a hyperelastic material model where the stresses in the material are balanced by the osmotic swelling tendencies of the glycosaminoglycans and the tensile restoring forces of a randomly-oriented crosslinked collagen fiber network. This study shows that the swelling response of the cervical tissue increased with decreasing PYD density in normal remodeling. In the Antxr2-/- mice, there was no significant increase in swelling volume or significant decrease in crosslink density with advancing gestation. By comparing the ECM-mechanical response relationships in normal and disrupted parturition mouse models this study shows that a reduction of collagen crosslink density is related to cervical softening and contributes to the cervical remodeling process.

Growth performance and carcass characteristics of guinea fowl broilers fed micronized-dehulled pea (Pisum sativum L.) as a substitute for soybean meal

This study was conducted to evaluate the effect of substitution of soybean meal (SBM) with dehulled-micronized peas (Pisum sativum) in diets of guinea fowl broilers on their growth performance, carcass yields, and fatty acid composition of meat. One hundred forty 1-d-old guinea fowl keets were randomly assigned to 2 dietary treatments, which were fed from hatch to 12 wk. The birds were fed 2 wheat middling-based diets comprising a control diet, which contained SBM (78 g/kg) and a test diet containing dehulled-micronized peas (180 g/kg) as the main protein source. The substitution of SBM with peas had no adverse effect on growth performance, dressing percentage, or breast and thigh muscle relative weights of the guinea broilers. However, a reduction of abdominal fat content (P < 0.05) was observed in birds fed the pea diet compared with the control. Breast and thigh meat of birds fed the pea diet had higher lightness scores (P < 0.05) and water-holding capacity (P < 0.01) than the control. Meat from guinea fowls fed the pea diet had less cholesterol (P < 0.01) and lipids (P < 0.05), and higher concentrations of phospholipids (P < 0.05). Feeding peas increased polyunsaturated fatty acid concentration in breast and thigh muscles, and decreased the saturated fatty acid concentration. Feeding the pea diet also lowered the n-6/n-3 polyunsaturated fatty acid ratio of the guinea broiler muscles. Our results suggest that replacing the conventional SBM as the protein source with dehulled-micronized pea meal in diets of guinea fowls broilers can improve carcass quality and favorable lipid profile without adversely affecting growth performance traits.

Assaying proline hydroxylation in recombinant collagen variants by liquid chromatography-mass spectrometry

Background

The fabrication of recombinant collagen and its prescribed variants has enormous potential in tissue regeneration, cell-matrix interaction investigations, and fundamental biochemical and biophysical studies of the extracellular matrix. Recombinant expression requires proline hydroxylation, a post-translational modification which is critical for imparting stability and structure. However, these modifications are not native to typical bacterial or yeast expression systems. Furthermore, detection of low levels of 4-hydroxyproline is challenging with respect to selectivity and sensitivity.

Results

We have developed a new liquid chromatography-mass spectrometry (LC-MS) method to evaluate proline hydroxylation in recombinant collagen. This assay was tested in different Saccharomyces cerevisiae expression systems to evaluate the effect of gene ratio between prolyl-4-hydroxylase and collagen on the extent of hydroxylation. These systems used a human collagen III gene that was synthesized de novo from oligonucleotides. The LC-MS assay does not require derivatization, uses only picomoles of sample, and can measure proline hydroxylation levels in recombinant and native collagen ranging from approximately 0% to 40%. The hydroxylation values obtained by LC-MS are as accurate and as precise as those obtained with the conventional method of amino acid analysis.

Conclusions

A facile, derivatization-free LC-MS method was developed that accurately determines the percentage of proline hydroxylation in different yeast expression systems. Using this assay, we determined that systems with a higher collagen-to-hydroxylase gene copy ratio yielded a lower percentage of hydroxylation, suggesting that a specifically balanced gene ratio is required to obtain higher hydroxylation levels.

Analysis of hydroxyproline in collagen hydrolysates

Hydroxyproline (Hyp) is an imino acid post-translationally formed by sequence-specific hydroxylases in the repeating collagen Gly-Xaa-Yaa triad present in all collagen types of all species. In both Xaa- and Yaa-positions, Pro is the most common residue, often oxidized to 4-Hyp in the Yaa- and rarely to 3-Hyp in the Xaa-positions. Here, we describe the qualitative and quantitative analysis of 3- and 4-Hyp-isomers by separating the free imino acids either with hydrophilic interaction chromatography (HILIC) or after derivatization with reversed-phase chromatography (RPC). In both cases, the compounds were detected by electrospray ionization mass spectrometry (ESI-MS).

Dehulled-micronised lupin (Lupinus albus L. cv. Multitalia) as the main protein source for broilers: influence on growth performance, carcass traits and meat fatty acid composition

BACKGROUND

A study was carried out to compare the effect of diets containing micronised-dehulled lupin (Lupinus albus L. cv. Multitalia) on growth performance, carcass yields and meat fatty acid profile of broiler chickens.

RESULTS

Hubbard strain chicks receiving from 14 d to slaughtering age (49 d) a wheat middlings-based diet containing either deffatted soybean meal (195 g kg(-1), control) or dehulled micromicronised lupins (240 g kg(-1)) as the main protein source were used. The inclusion of treated lupin meal in the diet did not result in lower growth rates of chicks. Lupin diet had no effect on dressing percentage, or breast and drumstick muscles relative weights, but a reduction of abdominal fat content was reported (P < 0.05). White and dark meats of birds fed lupin diet had significant (P < 0.05) lower L* (lightness) values and fat content (P < 0.05). Total collagen and water-holding capacity values were higher in lupin treatment. Feeding the lupin diet resulted in lower saturated fatty acid content in breast and drumstick meat, as well as the n-6/n-3 polyunsaturated fatty acid (PUFA) ratio and saturation, atherogenic and thrombogenic indexes, while total PUFA and monounsaturated fatty acids levels increased (P < 0.05).

CONCLUSION

These results suggest that replacing soybean meal with dehulled-micronised lupin meal in diet for broiler chickens can produce meat with favourable lipid profile and quality, with no adverse effects on productive parameters.

Simultaneous determination of 6 L-arginine metabolites in human and mouse plasma by using hydrophilic-interaction chromatography and electrospray tandem mass spectrometry

BACKGROUND

Macrophages and related cells are important cellular mediators of the innate immune system and play important roles in wound healing and fibrosis. Flux through different l-arginine metabolic pathways partially defines the functional behavior of macrophages. Methods to measure metabolites within the nitric oxide synthase/arginase pathways could provide insights into local and systemic inflammatory processes.

METHODS

A targeted metabolomics approach was developed by using hydrophilic-interaction liquid chromatography and electrospray ionization-tandem mass spectrometry to simultaneously measure l-arginine, asymmetric dimethylarginine, symmetric dimethylarginine, l-citrulline, l-ornithine, and l-proline in plasma from humans and mice.

RESULTS

All analytes were quantifiable in human and mouse plasma with a small volume (25 μL), minimal sample preparation, and no derivatization. Patients with high plasma concentrations of C-reactive protein and mice with acute inflammation induced by lipopolysaccharide had significant reductions of arginine metabolites in plasma compared with controls.

CONCLUSIONS

This new assay uses plasma metabolomic measurements to help provide new insights into metabolic changes coupled to the innate immune response. We identified significant changes in arginine metabolism in both humans and mice following an inflammatory stimulus. These changes were associated with decreased plasma arginine metabolite concentrations and increased methylated arginine concentrations.

Growth performance and carcass and meat quality of broiler chickens fed diets containing micronized-dehulled peas (Pisum sativum cv. Spirale) as a substitute of soybean meal

An experiment was carried out to evaluate the effects of diets containing peas on productive traits, carcass yields, and fatty acid profiles (breast and drumstick meat) of broiler chickens. Hubbard strain broiler chicks, divided into 2 groups, received from 14 d to slaughtering age (49 d) a wheat middlings-based diet containing soybean (190 g/kg) or micronized-dehulled peas (400 g/kg) as the main protein source. The inclusion of peas did not significantly change the growth performance of birds. The pea level had no effect on the dressing percentage, the percentage of breast or drumstick muscles, and abdominal fat. The muscles of birds fed the pea diet had significant (P < 0.05) lower L* (lightness) and b* (yellowness, drumstick muscle) values and fat content. Instead, total collagen and water-holding capacity values were higher in the pea treatment. The polyunsaturated fatty acid concentration in breast and drumstick muscles was significantly increased with the alternative protein source inclusion, whereas the saturated fatty acid was similar among treatments. The n-6/n-3 polyunsaturated fatty acid ratio of the broiler drumstick meat decreased significantly in the pea group. Dietary pea inclusion improved the saturation index of meat without altering atherogenic and thrombogenic indexes. It can be concluded that the pea treatment tested had a positive effect on the performance and meat quality of broiler chickens.

Biochemical evaluation of the therapeutic effectiveness of honey in oral mucosal ulcers

The aim of this study was to describe and quantify the therapeutic value of honey in oral mucosal ulcers healing in comparison with Glyceroloxytriester (TGO). We also aimed to biochemically evaluate the healing effects of honey which had been collected from the Blacksea region flora on mucosal ulcers resulting in material loss.Thirty wistar rats (240+/-30 g) were enrolled in this study. Excisional wounds were performed in all rats for animal oral mucosal ulcer model. They were randomly allocated to three groups: group 1 was treated with Apitherapeutic agent or honey (0,1 ml, 2x1), group 2 was treated with TGO (0,1ml, 2x1) locally, Group 3 served as the control group.Following the surgical procedure on day 7, biopsy specimens were taken from right buccal mucosa and on day 14 biopsy specimens were taken from left bucal mucosa in all rats. Afterwards, hydroxy pyroline levels were measured. Data were analyzed statistically.There was no statistically significant difference between Group 1 and 2, and also between Group 2 and 3, but there was statistically significant difference between Group 1 and 3 on day 7. There was no statistically significant difference between Group 1, 2 and 3 on day 14.

Hydroxyproline quantification for the estimation of collagen in tissue using multiple reaction monitoring mass spectrometry

Collagens are highly abundant mammalian proteins that contain a high content of hydroxylated amino acids such as hydroxyproline. We have exploited the high hydroxyproline content of collagen and developed a method for hydroxyproline quantification as a measure of collagen content in muscle samples. The novel method utilizes a highly selective and sensitive method of multiple reaction monitoring (MRM) by mass spectrometry. The analytical method is simple, rapid (5min), convenient (no derivatization), precise (<17% RSD), accurate (90-108%), sensitive (4.88nmol/L) and linear (R(2)>0.999) over three orders of magnitude (5-5000nmol/L).

Expression of transforming growth factor β1 gene, basic fibroblast growth factor gene and hydroxyproline in diabetes-induced bladder dysfunction in a rat model

AIMS

To investigate the content of hydroxyproline (Hyp) and the expression of transforming growth factor beta1 (TGF beta1) and basic fibroblast growth factor (bFGF) in the bladder 8 weeks after diabetes induction.

METHODS

Thirty wistar rats were divided into three groups: control (n = 10), streptozotocin-induced diabetic group (n = 10), TAD group (n = 10; diabetic rats were fed with Tadenan 100 mg kg(-1) day(-1)). Eight weeks later, the bladders were dissected. RT-PCR, immunohistochemistry, and ELISA were used to detect the expression of TGF beta1 and bFGF in the bladder. Also hydroxyproline (Hyp) was measured using a method based on alkaline hydrolysis.

RESULTS

The content of hydroxyproline in the diabetic group was greater than that of control group (P < 0.05); we found significantly increased expression of TGF beta1 mRNA and bFGF mRNA in the bladder from the diabetic group compared with the control group; immunohistochemical and ELISA studies showed a statistically significant increased expression of TGF beta1 protein and bFGF protein in the bladder from the diabetic group compared with the control group (P < 0.05). The content of hydroxyproline in TAD group was less than that of diabetic group (P < 0.05); mRNA expression of TGF beta1 and bFGF greatly decreased in TAD group compared with that of the diabetic group; immunohistochemical and ELISA studies showed decreased levels of TGF beta1 protein and bFGF protein in the bladder from TAD group compared with the diabetic group (P < 0.05).

CONCLUSIONS

Rats with streptozoticin-induced diabetes mellitus showed significant increase in hydroxyproline, TGF beta1 and bFGF levels in their bladders, which may be an important mechanism inducing diabetic cystopathy. Tadenan could effectively reduce hydroxyproline, TGF beta1, and bFGF levels.

Analysis of hydroxyproline isomers and hydroxylysine by reversed-phase HPLC and mass spectrometry

Collagens, the most abundant mammalian proteins, contain a high content of hydroxylated amino acids, such as, 3- and 4-cis-/trans-hydroxyproline (Hyp) and 5-hydroxylysine (Hyl). Whereas the global content of 4-Hyp was studied by amino acid analysis, no technique to determine all five hydroxyamino acids simultaneously in collagens has been reported. Here, we report the separation of all five hydroxyamino acids as well as two Hyp epimers from all other proteinogenic amino acids after derivatization with N(2)-(5-fluoro-2,4-dinitrophenyl)-l-valine amide (l-FDVA) by RPC-UV-ESI-MS. The general applicability of this method is shown for three Hyp-containing peptides as well as collagen type I.

Accurate determination of an immunosuppressant in stented swine tissues with LC–MS/MS

During stent development, accurate monitoring of the drug concentration in animal tissues can provide critical information on how the drug is released into the circulation and the surrounding tissues. To establish the relationship between the drug concentration and the distance from the stent to the target tissue, a comprehensive strategy was developed for sample collection, sample homogenization and sample storage as well as sample analysis. This strategy was developed with the analytical chemists and animal surgical specialists working together as a team. The optimized sampling process was designed to yield a representative sample, appropriately located and of an appropriate size. The sampling process was also designed to eliminate the potential for carryover and cross-contamination. During sample processing, the analyte solution was spiked into blank tissues using a sharp needle and a gas-tight syringe to prepare tissue quality control samples. These tissue quality controls were then used to evaluate the stability of the drug in solid tissue and homogenate, the homogenization carryover, the cross-contamination and the recovery of the drug during method validation and to monitor the overall process of drug analysis of the swine tissues. This thorough strategy has been applied to the accurate determination of zotarolimus in swine tissues for regulated toxicology studies. The entire process was controlled, including precise tissue sampling, compound-based tissue homogenization, method validation, and the application of the method to regulated toxicokinetics studies. The results demonstrate that analytical chemistry concepts can be successfully integrated into toxicokinetics studies in order to collect precise samples and obtain meaningful results. The strategy can be applied to similar toxicokinetics studies of locally administrated drugs in tissues.

Amino acid analysis by hydrophilic interaction chromatography coupled on-line to electrospray ionization mass spectrometry

Collagens form a common family of triple-helical proteins classified in 21 types. This unique structure is further stabilized by specific hydroxylation of distinct lysyl and prolyl residues forming 5-hydroxylysine and hydroxyproline (Hyp) isomers, mostly 4-trans and 3-trans-Hyp. The molecular distribution of the Hyp-isomers among the different collagen types is still not well investigated, even though disturbances in the hydroxylation of collagens are likely to be involved in several diseases such as osteoporosis and autoimmune diseases. Here, a new approach to analyze underivatized amino acids by hydrophilic interaction chromatography (HILIC) coupled on-line to electrospray ionization mass spectrometry (ESI-MS) is reported. This method can separate all three studied Hyp-isomers, Ile, and Leu, which are all isobaric, allowing a direct qualitative and quantitative analysis of collagen hydrolysates. The sensitivity and specificity was increased by a neutral loss scan based on the loss of formic acid (46 u).

Method development and validation for zotarolimus concentration determination in stented swine arteries by liquid chromatography/tandem mass spectrometry detection

Drug-eluting stents have attracted significant attention in the medical community and pharmaceutical industry due to their proven success in significantly reducing restenosis. Abbott Laboratories is developing a drug-eluting stent coated with zotarolimus and swine was recently used as an animal model for the pre-clinical study of stent implantation. In this article, we present a detailed experimental design and results for the validation and sample analysis of zotarolimus drug concentration in stented swine artery samples. Introduction of tissue quality control (QC) samples allows evaluation of the entire analytical process as well as the stability of the drug in both original tissue and homogenized tissue samples. In addition, a novel approach using 100% swine blood as the homogenization solution was developed for the consistency of the liquid-liquid extraction recovery and stability of the zotarolimus in tissue homogenates. Standards were prepared by spiking zotarolimus working solution in swine blood and tissue QC samples were used along with the artery samples during the sample analysis. The linear dynamic range of blood standard samples is from 0.61 to 333.20 ng/mL to accommodate the predicted artery homogenate concentrations. Overall tissue QC %CV during the method validation was from 4.4% to 8.6%. The overall %bias of tissue QC samples during the method validation was from -7.3% to 16.6%. The method was successfully applied for the analysis of swine artery samples. A similar approach for method validation and sample analysis has been successfully applied for the analysis of swine myocardium, kidney and liver tissue samples.