Relations Between Bone Quantity, Microarchitecture, and Collagen Cross‐links on Mechanics Following In Vivo Irradiation in Mice

A model system consisting of highly purified lysyl oxidase and reconstituted lathyritic chick bone collagen fibrils was used to study the effect of collagen cross-linking on collagen degradation by mammalian collagenase. The results indicate that synthesis of approx. 0.1 Schiff-base cross-link per collagen molecule results in a 2–3-fold resistance to human synovial collagenase when compared with un-cross-linked controls or samples incubated in the presence of beta-aminopropionitrile to inhibit cross-linking. These results confirm previous studies utilizing artificially cross-linked collagens, or collagens isolated as insoluble material after cross-linking in vivo, and suggest that increased resistance to collagenase may be one of the earliest effects of cross-linking in vivo. The extent of intermolecular cross-linking among collagen fibrils may provide a mechanism for regulating the rate of collagen catabolism relative to synthesis in normal and pathological conditions.

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Pericentric chromatin loops function as a nonlinear spring in mitotic force balance

The Journal of Cell Biology ◽

10.1083/jcb.201208163 ◽

2013 ◽

Vol 200 (6) ◽

pp. 757-772 ◽

Cited By ~ 48

Author(s):

Andrew D. Stephens ◽

Rachel A. Haggerty ◽

Paula A. Vasquez ◽

Leandra Vicci ◽

Chloe E. Snider ◽

...

Keyword(s):

Chromosome Segregation ◽

Spindle Assembly Checkpoint ◽

Force Balance ◽

Nonlinear Spring ◽

Sister Chromatids ◽

Spindle Dynamics ◽

Restoring Forces ◽

Cross Links ◽

Mean And Variance

The mechanisms by which sister chromatids maintain biorientation on the metaphase spindle are critical to the fidelity of chromosome segregation. Active force interplay exists between predominantly extensional microtubule-based spindle forces and restoring forces from chromatin. These forces regulate tension at the kinetochore that silences the spindle assembly checkpoint to ensure faithful chromosome segregation. Depletion of pericentric cohesin or condensin has been shown to increase the mean and variance of spindle length, which have been attributed to a softening of the linear chromatin spring. Models of the spindle apparatus with linear chromatin springs that match spindle dynamics fail to predict the behavior of pericentromeric chromatin in wild-type and mutant spindles. We demonstrate that a nonlinear spring with a threshold extension to switch between spring states predicts asymmetric chromatin stretching observed in vivo. The addition of cross-links between adjacent springs recapitulates coordination between pericentromeres of neighboring chromosomes.

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Effect of nitric oxide synthase inhibitors on bone metabolism in growing rats

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1996.270.5.e840 ◽

1996 ◽

Vol 270 (5) ◽

pp. E840-E845 ◽

Cited By ~ 5

Author(s):

H. Tsukahara ◽

M. Miura ◽

S. Tsuchida ◽

I. Hata ◽

K. Hata ◽

...

Keyword(s):

Nitric Oxide ◽

Bone Mass ◽

Bone Mineral ◽

Normal Serum ◽

Bone Mineral Status ◽

Growing Rats ◽

Bone Mineral Mass ◽

Bone Degradation ◽

Cross Links

We examined the effects of chronic nitric oxide (NO) blockade on bone mineral status in growing rats. Oral administration of NG-nitro-L-arginine methyl ester (L-NAME) for 4 wk caused hypertension and a significant reduction in urinary NO2- and NO3- excretion. Four-week oral aminoguanidine (AG, 400 mg/dl of drinking water) did not alter blood pressure but caused a significant decrease in urinary NO2- and NO3-. Rats treated with L-NAME at doses of 20 and 50 mg/dl had normal bone mineral mass in the lumbar spine, but the highest dose (80 mg/dl) caused a slight decrease in bone mass. Chronic AG induced a significant spine osteopenia. This effect of AG was abolished by the simultaneous administration of L-arginine (2.0 g/dl). AG-induced osteopenia was associated with a significant increase in urine excretion of collagen cross-links with normal serum osteocalcin. These findings indicate that chronic AG administration can cause an imbalance between bone resorption and formation, resulting in a decrease in bone mass in growing rats, and suggest that NO produced by inducible NO synthase plays an important role in basal osteoclast bone degradation activity in vivo.

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Age-related changes in collagen synthesis and degradation in rat tissues. Importance of degradation of newly synthesized collagen in regulating collagen production

Biochemical Journal ◽

10.1042/bj2760307 ◽

1991 ◽

Vol 276 (2) ◽

pp. 307-313 ◽

Cited By ~ 120

Author(s):

P K Mays ◽

R J McAnulty ◽

J S Campa ◽

G J Laurent

Keyword(s):

Skeletal Muscle ◽

Collagen Synthesis ◽

Rat Tissues ◽

Age Related ◽

Developmental Growth ◽

Cross Links ◽

Fractional Synthesis ◽

Synthesis And Degradation ◽

Age Related Changes

During developmental growth, collagens are believed to be continuously deposited into an extracellular matrix which is increasingly stabilized by the formation of covalent cross-links throughout life. However, the age-related changes in rates of synthetic and degradative processes are less well understood. In the present study we measured rates of collagen synthesis in vivo using a flooding dose of unlabelled proline given with [14C]proline and determining production of hydroxy[14C]proline. Degradation of newly synthesized collagen was estimated from the amount of free hydroxy [14C]proline in tissues 30 min after injection. Collagen fractional synthesis rates ranged from about 5%/day in skeletal muscle to 20%/day in hearts of rats aged 1 month. At 15 months of age, collagen fractional synthesis rates had decreased markedly in lung and skin, but in skeletal muscle and heart, rates were unchanged. At 24 months of age, synthesis rates had decreased by at least 10-fold in all tissues, compared with rates at 1 month. The proportion of newly synthesized collagen degraded ranged from 6.4 +/- 0.4% in skin to 61.6 +/- 5.0% in heart at 1 month of age. During aging the proportion degraded increased in all tissues to maximal values at 15 months, ranging from 56 +/- 7% in skin to 96 +/- 1% in heart. These data suggest that there are marked age-related changes in rates of collagen metabolism. They also indicate that synthesis is active even in old animals, where the bulk of collagens produced are destined to be degraded.

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The detection of DNA-protein cross-links in rat tracheal implants exposed in vivo to benzo[a]pyrene and formaldehyde

Cancer Letters ◽

10.1016/0304-3835(88)90233-9 ◽

1988 ◽

Vol 42 (1-2) ◽

pp. 13-21 ◽

Cited By ~ 7

Author(s):

G.N. Cosma ◽

A.S. Wilhite ◽

A.C. Marchok

Keyword(s):

Cross Links

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Fragility and structure of hemoglobin S fibers and gels and their consequences for gelation kinetics and rheology

Blood ◽

10.1182/blood.v83.2.573.573 ◽

1994 ◽

Vol 83 (2) ◽

pp. 573-579 ◽

Cited By ~ 12

Author(s):

RW Briehl ◽

AE Guzman

Keyword(s):

Delay Time ◽

Hemoglobin Concentration ◽

Differential Interference Contrast ◽

Cell Disease ◽

Mechanical Perturbation ◽

Hemoglobin S ◽

Gelation Kinetics ◽

A Value ◽

Cross Links

Abstract Pathogenesis in sickle cell disease depends on whether red blood cells can pass the microvasculature during the delay time before hemoglobin S gelation and cell rigidification occur. Here we observe individual hemoglobin S fibers by differential interference contrast (DIC) microscopy and show that hemoglobin S gels and fibers are fragile and easily broken by mechanical perturbation, and that breakage results in vast acceleration of gelation kinetics due to the creation of new, growing fiber-ends. Hence, in vivo this may be an important factor, in addition to hemoglobin concentration and degree of deoxygenation, that governs delay time and pathogenesis. Pathogenesis also depends on gel rheology and cell rigidification, which depend on fiber cross-linking. We show different mechanisms by which X-shaped, Y-shaped, and “zippering” cross-links form. Finally, we estimate the “on” rate constant for fiber growth to be about 200 mmol/(L.s) and obtain a value for the heterogeneous nucleation rate at 13.5 mmol/L heme.

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Ethyl Pyruvate Prevents Renal Damage Induced by Methylglyoxal-Derived Advanced Glycation End Products

Journal of Diabetes Research ◽

10.1155/2019/4058280 ◽

2019 ◽

Vol 2019 ◽

pp. 1-9

Author(s):

Eunsoo Jung ◽

Wan Seok Kang ◽

Kyuhyung Jo ◽

Junghyun Kim

Keyword(s):

Advanced Glycation End Products ◽

Ethyl Pyruvate ◽

Renal Diseases ◽

Dependent Manner ◽

Advanced Glycation ◽

Glycation End Products ◽

End Products ◽

Cross Links

The renal accumulation of advanced glycation end products (AGEs) is a causative factor of various renal diseases, including chronic kidney disease and diabetic nephropathy. AGE inhibitors, such as aminoguanidine and pyridoxamine, have the therapeutic activities for reversing the increase in renal AGE burden. This study evaluated the inhibitory effects of ethyl pyruvate (EP) on methylglyoxal- (MGO-) modified AGE cross-links with proteins in vitro. We also determined the potential activity of EP in reducing the renal AGE burden in exogenously MGO-injected rats. EP inhibited MGO-modified AGE-bovine serum albumin (BSA) cross-links to collagen (IC50=0.19±0.03 mM) in a dose-dependent manner, and its activity was stronger than aminoguanidine (IC50=35.97±0.85 mM). In addition, EP directly trapped MGO (IC50=4.41±0.08 mM) in vitro. In exogenous MGO-injected rats, EP suppressed AGE burden and MGO-induced oxidative injury in renal tissues. These activities of EP on the MGO-mediated AGEs cross-links with protein in vitro and in vivo showed its pharmacological potential for inhibiting AGE-induced renal diseases.

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Haemocytes play a commensal rôle in the synthesis of the dihydroxybenzoate required as a precursor for sclerotization of the egg case (ootheca) in the cockroach Periplaneta americana (L)

Bulletin of Entomological Research ◽

10.1017/s0007485310000246 ◽

2010 ◽

Vol 101 (3) ◽

pp. 251-258 ◽

Cited By ~ 1

Author(s):

D.L. Whitehead

Keyword(s):

Periplaneta Americana ◽

Calcium Oxalate Crystals ◽

Adult Females ◽

Thin Section Electron Microscopy ◽

Section Electron ◽

Cross Links ◽

Phenolic Glucoside ◽

Egg Case ◽

Section Electron Microscopy

AbstractThe secretions of the two colleterial glands give rise to the walls of the ootheca which, when hardened, serve to protect fertilised eggs in the cockroach P. americana. The larger left gland (LCG) secretes a β-D-glucoside of 3,4-dihydroxybenzoate, several proteins (oothecins), calcium oxalate crystals and a latent phenoloxidase enzyme. The smaller right gland (RCG) secretes a β-glucosidase. When the two secretions mix in the genital vestibulum, the glucoside is hydrolyzed to glucose and free dihydroxybenzoate, which is then oxidized by the phenoloxidase to the o-benzoquinone, which cross-links the oothecins Scanning and thin section electron microscopy (EM) showed haemocytes adhering to the LCG. The haemocytes were obtained by washing the gland with insect saline; and, when they were incubated with labelled tyrosine, they showed an enhanced ability to decarboxylate L-p-tyrosine to tyramine and then deaminate and oxidize tyramine to give p-hydroxyphenylacetate. After removal of adhering haemocytes, the LCG was no longer able to decarboxylate tyrosine. Injection of α-ecdysone into the abdomens of recently emerged adult females inhibited synthesis of a phenolic glucoside in the developing LCG but not of β-glucosidase produced by RCG. Furthermore, injecting inhibitors of the decarboxylase and monoamineoxidase enzymes partly closed down synthesis in vivo of the phenolic glucoside by LCG. Therefore, in the adult female cockroach, tyramine was converted to p-hydroxyphenylacetate in the haemocytes and then transferred to the gland where it was hydroxylated to 3,4-dihydroxyphenylacetate, which gave rise to a dihydroxybenzoate. Evidence suggested that biosynthesis of the oothecal sclerotizing agent could be controlled by juvenile hormone (JH) acting on the LCG or on haemocytes adhering to the gland.

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Cross-linking modifications of HDL apoproteins by oxidized phospholipids: structural characterization, in vivo detection, and functional implications

Journal of Biological Chemistry ◽

10.1074/jbc.ra119.008445 ◽

2020 ◽

Vol 295 (7) ◽

pp. 1973-1984

Author(s):

Detao Gao ◽

Mohammad Z. Ashraf ◽

Lifang Zhang ◽

Niladri Kar ◽

Tatiana V. Byzova ◽

...

Keyword(s):

Density Lipoprotein ◽

Cross Linking ◽

Oxidized Phospholipids ◽

Cross Link ◽

In Vivo Detection ◽

Lysine Residues ◽

Cross Links ◽

Human Atheroma

Apolipoprotein A-I (apoA-I) is cross-linked and dysfunctional in human atheroma. Although multiple mechanisms of apoA-I cross-linking have been demonstrated in vitro, the in vivo mechanisms of cross-linking are not well-established. We have recently demonstrated the highly selective and efficient modification of high-density lipoprotein (HDL) apoproteins by endogenous oxidized phospholipids (oxPLs), including γ-ketoalkenal phospholipids. In the current study, we report that γ-ketoalkenal phospholipids effectively cross-link apoproteins in HDL. We further demonstrate that cross-linking impairs the cholesterol efflux mediated by apoA-I or HDL3 in vitro and in vivo. Using LC-MS/MS analysis, we analyzed the pattern of apoprotein cross-linking in isolated human HDL either by synthetic γ-ketoalkenal phospholipids or by oxPLs generated during HDL oxidation in plasma by the physiologically relevant MPO-H2O2-NO2− system. We found that five histidine residues in helices 5–8 of apoA-I are preferably cross-linked by oxPLs, forming stable pyrrole adducts with lysine residues in the helices 3–4 of another apoA-I or in the central domain of apoA-II. We also identified cross-links of apoA-I and apoA-II with two minor HDL apoproteins, apoA-IV and apoE. We detected a similar pattern of apoprotein cross-linking in oxidized murine HDL. We further detected oxPL cross-link adducts of HDL apoproteins in plasma and aorta of hyperlipidemic LDLR−/− mice, including cross-link adducts of apoA-I His-165–apoA-I Lys-93, apoA-I His-154–apoA-I Lys-105, apoA-I His-154–apoA-IV Lys-149, and apoA-II Lys-30–apoE His-227. These findings suggest an important mechanism that contributes to the loss of HDL's atheroprotective function in vivo.

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Genetic interaction mapping informs integrative structure determination of protein complexes

Science ◽

10.1126/science.aaz4910 ◽

2020 ◽

Vol 370 (6522) ◽

pp. eaaz4910 ◽

Cited By ~ 1

Author(s):

Hannes Braberg ◽

Ignacia Echeverria ◽

Stefan Bohn ◽

Peter Cimermancic ◽

Anthony Shiver ◽

...

Keyword(s):

Rna Polymerase ◽

Rna Polymerase Ii ◽

Structure Determination ◽

Genetic Interaction ◽

Protein Complexes ◽

Point Mutations ◽

Genetic Interactions ◽

Cellular Functions ◽

Cross Links

Determining structures of protein complexes is crucial for understanding cellular functions. Here, we describe an integrative structure determination approach that relies on in vivo measurements of genetic interactions. We construct phenotypic profiles for point mutations crossed against gene deletions or exposed to environmental perturbations, followed by converting similarities between two profiles into an upper bound on the distance between the mutated residues. We determine the structure of the yeast histone H3-H4 complex based on ~500,000 genetic interactions of 350 mutants. We then apply the method to subunits Rpb1-Rpb2 of yeast RNA polymerase II and subunits RpoB-RpoC of bacterial RNA polymerase. The accuracy is comparable to that based on chemical cross-links; using restraints from both genetic interactions and cross-links further improves model accuracy and precision. The approach provides an efficient means to augment integrative structure determination with in vivo observations.

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