Intermittent Hypoxia Alleviates ß-Aminopropionitrile Monofumarate Induced Thoracic Aortic Dissection in C57BL/6 Mice.

OBJECTIVE: Thoracic aortic dissection (TAD) has a high mortality rate. Intermittent hypoxia (IH) triggers both harmful and beneficial effects in numerous physiological systems. The effects of IH on TAD development were explored in a mouse model. METHODS: ß-Aminopropionitrile monofumarate (BAPN) was used to induce TAD in C57BL/6 mice. Three week old male mice were treated with 1 g/kg/day BAPN in drinking water for four weeks and simultaneously subjected to IH (n = 30) (21%-5% O2, 90 s/cycle, 10 h/day, IH + BAPN group) or normoxia (n = 30) (21% O2, 24 h/day, BAPN group). Human VSMCs (HUASMCs) exposed to IH (30 min, 5% O2)/re-oxygenation (30 min, 21% O2) cycles with a maximum of 60 min/cycle to detect the effect of IH on HIF-1α and LOX via HIF-1α-siRNA. RESULTS: It was found that BAPN administration significantly increased the lumen size and wall thickness of aortas compared with the normal group, but was significantly reversed by IH exposure. Additionally, IH exposure significantly increased the survival rate of BAPN induced TAD (70% vs. 40%). Furthermore, IH exposure reduced BAPN induced elastin breaks and apoptosis of vascular smooth muscle cells. IH exposure also reversed BAPN induced upregulation of inflammation and extracellular matrix (ECM) degradation. Real time polymerase chain reaction (RT-PCR) confirmed that IH inhibited inflammation and ECM degradation related genes interleukin (IL)-1ß, IL-6, cathepsin S (Cat S), and matrix metalloproteinase 9 (MMP-9), but upregulated the ECM synthesis related genes lysyl oxidase (LOX) and collagen type I alpha2 (Col1a2) compared with the BAPN group. In vitro results suggest that IH promotes the expression of LOX via HIF-1α. CONCLUSION: The results suggest that IH alleviates BAPN induced TAD in C57BL/6 mice.

The Effect of Polydeoxyribonucleotide Extracted from Salmon Sperm on the Restoration of Bisphosphonate-Related Osteonecrosis of the Jaw.

Bisphosphonates (BPs) used for treating skeletal diseases can induce bisphosphonate-related osteonecrosis of the jaw (BRONJ). Despite much effort, effective remedies are yet to be established. In the present study, we investigated the feasibility of polydeoxyribonucleotide (PDRN) extracted from salmon sperm for the treatment of BRONJ, in a BRONJ-induced rat model. Compared with BRONJ-induced samples, PDRN-treated samples exhibited lower necrotic bone percentages and increased numbers of blood vessels and attached osteoclast production. Moreover, local administration of PDRN at a high concentration (8 mg/kg) remarkably resolved the osteonecrosis. Findings from this study suggest that local administration of PDRN at a specific concentration may be considered clinically for the management of BRONJ.

A novel chronic advanced stage abdominal aortic aneurysm murine model.

OBJECTIVE: The purpose of this study was to establish a reliable, chronic model of abdominal aortic aneurysm (AAA). METHODS: Wild-type 8-week-old C56BL/6 male mice (n = 120) were equally divided into three groups: (1) BAPN group: 0.2% 3-aminopropionitrile fumarate salt (BAPN) drinking water was provided to mice 2 days before surgery until the end of study. Sham aneurysm induction surgery was performed using 5 µL of heat deactivated elastase. (2) Elastase group: mice were given regular drinking water without BAPN. During aneurysm induction surgery, 5 µL of the active form of elastase (10.3 mg protein/mL, 5.9 U/mg protein) was applied on top of the infrarenal abdominal aorta adventitia for 5 minutes. (3) BAPN+elastase group: mice were given BAPN drinking water and the active form of elastase application, as above. On postoperative days 7, 14, 21, 28, and 100, aortic samples were collected for histology, cytokine array, and gelatin zymography after aortic diameter measurement. RESULTS: Compared with the elastase group, the BAPN+elastase group had a higher AAA formation rate (93% vs 65%; P < .01) with more advanced AAAs (25 of 42 vs 1 of 40 for stage II and III; P < .001). Aneurysms from the BAPN+elastase group demonstrated persistent long-term growth (221.5% ± 36.6%, 285.8% ± 78.6%, and 801% ± 160% on days 21, 28, and 100, respectively; P < .001), with considerable thrombus formation (54%) and rupture (31%) at the advanced stages of AAA development. Cytokine levels (pro-matrix metalloproteinase 9, interleukin-1ß, interleukin-6, chemokine [C-C motif] ligand 5, triggering receptor expressed on myeloid cells 1, monocyte chemotactic protein 1, and tissue inhibitor of metalloproteinase 1) in the BAPN+elastase group were higher than in the elastase group on day 7. After day 7, cytokine levels returned to baseline, with the exception of elevated matrix metalloproteinase 2 activity. By histology, CD3-positive T cells in the BAPN+elastase group were elevated on days 28 and 100. CONCLUSIONS: A combination of oral BAPN administration and periaortic elastase application induced a chronic, advanced-stage AAA with characteristics of persistent aneurysm growth, thrombus formation, and spontaneous rupture. Future studies should use this model, especially for examining tissue remodeling during the late stages of aneurysm development.

Adventitial CXCL1/G-CSF expression in response to acute aortic dissection triggers local neutrophil recruitment and activation leading to aortic rupture.

RATIONALE: In-hospital outcomes are generally acceptable in patients with type B dissection; however, some patients present with undesirable complications, such as aortic expansion and rupture. Excessive inflammation is an independent predictor of adverse clinical outcomes. OBJECTIVE: We have investigated the underlying mechanisms of catastrophic complications after acute aortic dissection (AAD) in mice. METHODS AND RESULTS: When angiotensin II was administered in lysyl oxidase inhibitor-preconditioned mice, AAD emerged within 24 hours. The dissection was initiated at the proximal site of the descending thoracic aorta and propagated distally into an abdominal site. Dissection of the aorta caused dilatation, and ≈70% of the mice died of aortic rupture. AAD triggered CXCL1 and granulocyte-colony stimulating factor expression in the tunica adventitia of the dissected aorta, leading to elevation of circulating CXCL1/granulocyte-colony stimulating factor levels. Bone marrow CXCL12 was reduced. These chemokine changes facilitated neutrophil egress from bone marrow and infiltration into the aortic adventitia. Interference of CXCL1 function using an anti-CXCR2 antibody reduced neutrophil accumulation and limited aortic rupture post AAD. The tunica adventitia of the expanded dissected aorta demonstrated high levels of interleukin-6 (IL-6) expression. Neutrophils were the major sources of IL-6, and CXCR2 neutralization significantly reduced local and systemic levels of IL-6. Furthermore, disruption of IL-6 effectively suppressed dilatation and rupture of the dissected aorta without any influence on the incidence of AAD and neutrophil mobilization. CONCLUSIONS: Adventitial CXCL1/granulocyte-colony stimulating factor expression in response to AAD triggers local neutrophil recruitment and activation. This leads to adventitial inflammation via IL-6 and results in aortic expansion and rupture.

Dynamic autophagic activity affected the development of thoracic aortic dissection by regulating functional properties of smooth muscle cells.

The aortic medial degeneration is the key histopathologic feature of Thoracic aortic dissection (TAD). The aim of this study was to identify the change of autophagic activity in the aortic wall during TAD development, and to explore the roles of autophagy on regulating functional properties of smooth muscle cells (SMCs). Firstly, compared with control group (n = 11), the increased expression of autophagic markers Beclin1 and LC3 was detected in the aortic wall from TAD group (n = 23) by immunochemistry and western blot. We found that more autophagic vacuoles were present in the aortic wall of TAD patients using Transmission electron microscopy. Next, autophagic activity was examined in AD mice model established by ß-aminopropionitrile fumarate (BAPN) and angiotensin II. Immunochemistry proved that autophagic activity was dynamically changed during AD development. Beclin1 and LC3 were detected up-regulated in the aortic wall in the second week after BAPN feeding, earlier than the fragmentation or loss of elastic fibers. When AD occurred in the 4th week, the expression of Beclin1 and LC3 began to decrease, but still higher than the control. Furthermore, autophagy was found to inhibit starvation-induced apoptosis of SMCs. Meanwhile, blockage of autophagy could suppress PDGF-induced phenotypic switch of SMCs. Taken together, autophagic activity was dynamically changed in the aortic wall during TAD development. The abnormal autophagy could regulate the functional properties of aortic SMCs, which might be the potential pathogenesis of TAD.

Induction of large cerebral aneurysms by intraperitoneal administration of ß-aminopropionitrile fumarate in male rats.

BACKGROUND: It is necessary and useful to obtain an experimental model which steadily and rapidly induces aneurysms for investigation of the pathogenesis of cerebral aneurysm. We attempted to examine whether intraperitoneal administration of ß-aminopropionitrile fumarate (BAPN-F) with additional treatments of induced hypertension and hemodynamic stress could steadily and rapidly induce aneurysms in male rats. METHODS: Seven-week-old male Sprague-Dawley rats pretreated with ligation of left common carotid and bilateral posterior renal arteries were administrated BAPN-F intraperitoneally. Induction rate and size of aneurysms was investigated with varying dose and duration of BAPN-F administration (low dose; 400 mg/kg/week for 4 or 8 weeks and high dose; 2800 mg/kg/week for 8 or 12 weeks). RESULTS: Induction rate in the high-dose groups was significantly higher (P<0.01) than that in the low-dose groups. Making comparisons between 8 and 12 weeks of the high-dose groups, while there was no difference in induction rate (8 weeks; 85.2% vs. 12 weeks; 76.9%), aneurysmal size was larger in 12 weeks (8 weeks; 127.5 µm, vs. 12 weeks; 181.7 µm in terms of median) but lethal intrathoracic hemorrhage was increased in 12 weeks (8 weeks; 7.4% vs. 12 weeks; 30.8%). Induction rate of large aneurysm was 22.2% and 30.8% in 8 and 12 weeks of the high-dose groups, respectively. CONCLUSIONS: High-dose BAPN-F administration can cause high-frequency aneurysmal induction. Although there was the difference in size and mortality rate based on administration duration, intraperitoneal administration of 2800 mg/kg/week BAPN-F for 8 weeks would be suitable for aneurysmal induction.

Progression and Regression of Abdominal Aortic Aneurysms in Mice.

OBJECTIVE: Abdominal aortic aneurysm (AAA) is a significant medical problem with a high mortality rate. Nevertheless, the underlying mechanism for the progression and regression of AAA is unknown. METHODS: Experimental model of AAA was first created by porcine pancreatic elastase incubation around the infrarenal aorta of C57BL/6 mice. Then, AAA progression and regression were evaluated based on the diameter and volume of AAA. The aortas were harvested for hematoxylin-eosin staining (HE), orcein staining, sirius red staining, immunofluorescence analysis and perls' prussian blue staining at the indicated time point. Finally, ß-aminopropionitrile monofumarate (BAPN) was used to explore the underlying mechanism of the regression of AAA. RESULTS: When we extended the observation period to 100 days, we not only observed an increase in the AAA diameter and volume in the early stage, but also a decrease in the late stage. Consistent with AAA diameter and volume, the aortic thickness showed the same tendency based on HE staining. The elastin and collagen content first degraded and then regenerated, which corresponds to the early deterioration and late regression of AAA. Then, endogenous up-regulation of lysyl oxidase (LOX) was detected, accompanying the regression of AAA, as detected by an immunofluorescent assay. BAPN and LOX inhibitor considerably inhibited the regression of AAA, paralleling the degradation of elastin lamella and collagen. CONCLUSION: Taken together, we tentatively conclude that endogenous re-generation of LOX played an influential role in the regression of AAA. Therefore, regulatory factors on the generation of LOX exhibit promising therapeutic potential against AAA.

Anti-lysyl oxidase combined with a vacuum device induces penile lengthening by remodeling the tunica albuginea.

This study aimed to explore whether and how anti-lysyl oxidase (anti-LOX) combined with a vacuum device (VD) could promote penile lengthening and to evaluate the effect on erectile function. This study was performed on four groups of adult rats: control, anti-LOX, VD (negative pressure value of -300 mmHg), and anti-LOX + VD. Penile length was measured by a modified VD method and verified on exposed length data. Intracavernous pressure (ICP) and maximum ICP/mean arterial pressure (MAP) ratio were recorded to assess erectile function. For corpus cavernosum, LOX activity and concentrations of pyridinoline, desmosine, hydroxyproline, and elastin were analyzed; transmission electron microscope and Hart's elastin staining were performed to monitor microstructural changes. Anti-LOX and VD significantly lengthened the penis by 10.8% (3.75 mm) and 8.2% (2.48 mm) compared with the control group, respectively, while anti-LOX + VD achieved the longest penile size (40.58 ± 0.40 mm) which was 17.4% longer than the control group (34.58 ± 0.54 mm). After 1-week washout, no penile retraction was observed. Meanwhile, exposed penile length data confirmed that the penis in the anti-LOX + VD group was also significantly longer. Anti-LOX inhibited LOX activity to reduce pyridinoline level, which led the penile tunica albuginea remodeling. However, it had no effect on hydroxyproline, desmosine, and elastin levels. Moreover, anti-LOX had no impact on erectile function, which was determined by ICP and ICP/MAP ratio. These results suggest that anti-LOX elongates the penis by reducing pyridinoline, which induces tunica albuginea remodeling. This lengthening effect was more obvious when combined with a VD. All procedures had no impact on erectile function.

Effects of Extracellular Matrix Softening on Vascular Smooth Muscle Cell Dysfunction.

Vascular smooth muscle cells (VSMCs) shift from a physiological contractile phenotype to an adverse proliferative or synthetic state, which is a major event leading to aortic disease. VSMCs are exposed to multiple mechanical signals from their microenvironment including vascular extracellular matrix (ECM) stiffness and stretch which regulate VSMC contraction. How ECM stiffness regulates the function and phenotype of VSMCs is not well understood. In this study, we introduce in vitro and in vivo models to evaluate the impact of ECM stiffnesses on VSMC function. Through unbiased transcriptome sequencing analysis, we detected upregulation of synthetic phenotype-related genes including osteopontin, matrix metalloproteinases, and inflammatory cytokines in VSMCs cultured using soft matrix hydrogels in vitro, suggesting VSMC dedifferentiation toward a synthetic phenotype upon ECM softening. For the in vivo model, the lysyl oxidase inhibitor ß-aminopropionitrile monofumarate (BAPN) was administrated to disrupt the cross-linking of collagen to induce ECM softening. Consistently, decreased ECM stiffnesses promoted VSMC phenotypic switching to a synthetic phenotype as evidenced by upregulation of synthetic phenotype-related genes in the aortas of mice following BAPN treatment. Finally, BAPN-treated mice showed severe expansion and developed aortic dissection. Our study reveals the pivotal role of ECM softening in regulating the VSMC phenotype switch and provides a potential target for treating VSMC dysfunction and aortic dissection disease.

Scavenger receptor A1 attenuates aortic dissection via promoting efferocytosis in macrophages.

Macrophage class A1 scavenger receptor (SR-A1) is a pattern recognition receptor with an anti-inflammatory feature in cardiovascular diseases. However, its role in acute aortic dissection (AD) is not known yet. Using an aortic dissection model in SR-A1-deficient mice and their wild type littermates, we found that SR-A1 deficiency aggravated beta-aminopropionitrile monofumarate induced thoracic aortic dilation, false lumen formation, extracellular matrix degradation, vascular inflammation and accumulation of apoptotic cells. These pathological changes were associated with an impaired macrophage efferocytosis mediated by tyrosine-protein kinase receptor Tyro3 in vitro and in vivo. SR-A1 could directly interact with Tyro3 and was required for Tyro3 phosphorylation to activate its downstream PI3K/Akt signaling pathway. Importantly, co-culture of SR-A1-/- macrophages with apoptotic Jurkat cells resulted in less devoured apoptotic cells accompanied by swelling mitochondria and damaged ATP generation, following poor IL-10 and robust TNF-α production. Deficiency of SR-A1 did not influence phagolysosome formation during the efferocytosis. Lentiviral overexpression of Tyro3 in SR-A1-/- macrophages induced restorative phagocytosis in vitro. Administration of Tyro3 agonist protein S could restore SR-A1-/- macrophages phagocytosis in vitro and in vivo. These findings suggest that SR-A1-Tyro3 axis in macrophages mitigate AD damage by promoting efferocytosis and inhibiting inflammation.

Lathyrogens and the role of collagen in the eruption of rat incisors.

Collagen fibres in the periodontal ligament may have two functions: to resist displacing forces and to cause the tooth to erupt. Their function was examined in the continuously-erupting incisor of the rat using various concentrations and types of lathyrogens. Lathyrogens retarded tooth eruption and increased the quantity of salt-soluble collagen in the ligament, indicating inhibition of the maturation of salt-soluble (young) collagen into salt-insoluble (old) collagen, which would lead to reduction in the tensile strength of the fibres and decrease resistance to occlusal forces. The easy extractability of the teeth is explained by the greater susceptibility to lathyrogens of the fibres in the alveolar-related part of the periodontal ligament, compared with those in the other parts.

Inhibition of collagen cross-linking: a new approach to ocular scarring.

A method for the production of alkali-induced conjunctival scarring in rabbits with minimal corneal involvement is presented. The lathyritic agent Beta-aminopropionitrile (BAPN), an inhibitor of collagen cross-linking, was applied topically for a period of 21 days after induction of injury. There was a statistically significant (p less than .025) increase in both the interpalpebral fissure length and width of scarred treated animals compared with the scarred control group. BAPN did not affect the interpalpebral fissure measurements of unscarred rabbit eyes. No clinical adverse effects were observed after the treatment period. Histological evaluation of the treated scar tissue was consistent with lathyrism.

Follow-up studies of workers with bladder neuropathy caused by exposure to dimethylaminopropionitrile.

Following a 1978 outbreak of bladder neuropathy among workers exposed to dimethyl-aminopropionitrile (DMAPN), follow-up studies were performed 2 a after the original epidemic to evaluate the persistence of symptoms among a small group of initially affected workers. Although the overall prevalence of urologic and neurological symptoms fell for the 11 persons interviewed, significantly high rates of persistent symptoms were seen. Of particular concern was the increase in the prevalence of symptoms of sexual dysfunction. Physical examination identified one individual with sensorimotor neuropathy which was initially detected 2 a earlier. Three individuals who had similar neuropathic findings in 1978 were normal 2 a later. Objective neurophysiological and urologic testing revealed evidence of persistent abnormalities in several workers, but most of the objective findings had improved over the 2-a period. The follow-up of residual effects of occupational exposure to neurotoxic substances is essential to the understanding of the course of occupational illnesses.

Effect of topical beta APN application on evoked potential conduction in rat sciatic nerve and spinal cord.

The purpose of this study is to evaluate possible toxic effects of beta-aminopropionitrile fumarate (beta APN), a lathyrogenic agent that inhibits fibrosis. This drug has been considered for use as an adjunct to surgical repair after topical application upon peripheral and central nervous system structures. In vivo and in vitro studies were done using rats to study the dose dependent neurotoxicity of this water soluble chemical. The results indicate that when the neural sheaths are removed the amplitude of the evoked sciatic nerve potential is irreversibly suppressed from 1 to 10 mM concentrations of beta APN. Nerve conduction velocities are relatively less affected with reduction from 43 to 35 m/sec by beta APN immersion. Similarly, the spinal cord studies show that when the dura and arachnoid are opened and damaged, 0.1 mM beta APN causes increased latency (from 9.9 to 14.5 msec) and decreased amplitude (from 79.4 to 56.8 microV) of cortical somatosensory evoked potentials. Possible mechanisms for the neurotoxic effects of beta APN are discussed.

Diagnosis of induced cleft palate in rats from defective patterns of differentiation of isoenzymes.

Cleft palate was induced in 420 embryos of Sprague-Dawley rats with a single oral dose of 600 mg/kg beta-aminoproprionitrile (BAPN) on embryonal day 15, 7 hours. The cleft palate was accompanied by a pathological differentiation pattern of various isoenzymes in palatal shelves. These isoenzymes could be detected in amniotic fluid from the 16th to the 20th days of pregnancy when they also had a pathological differentiation pattern. We conclude that teratogenically induced cleft palate in rats is accompanied by a pathological differentiation pattern that can be traced by determination of isoenzymes in the palatal shelves as well as in amniotic fluid.