Citron Rho-interacting kinase mediates arsenite-induced decrease in endothelial nitric oxide synthase activity by increasing phosphorylation at threonine 497: Mechanism underlying arsenite-induced vascular dysfunction

We reported that arsenite causes an acute decrease in nitric oxide (NO) production by increasing phosphorylation of endothelial NO synthase at threonine 497 (eNOS-Thr(497)); however, the detailed mechanism has not yet been clarified. Here, we investigated the kinase involving in arsenite-stimulated eNOS-Thr(497) phosphorylation. Although treatment with H-89, a known protein kinase A (PKA) inhibitor, inhibited arsenite-stimulated eNOS-Thr(497) phosphorylation, no inhibition was found in cells treated with other PKA inhibitors, including Rp-8-Br-cAMPS or PKI. Based on previous reports, we also tested whether RhoA mediates arsenite-stimulated eNOS-Thr(497) phosphorylation and found that arsenite causes an acute increase in RhoA activity. Ectopic expression of dominant negative (DN)-RhoA significantly reversed arsenite-stimulated eNOS-Thr(497) phosphorylation. An in vitro phosphorylation assay also revealed that the well-known Rho effectors, Rho-associated protein kinase 1/2 (ROCK1/2), directly phosphorylate eNOS-Thr(497). Y27632, a selective ROCK inhibitor, reversed arsenite-stimulated eNOS-Thr(497) phosphorylation. However, overexpression of a small interfering RNA (siRNA) against ROCK1/2 or DN-ROCK did not reverse arsenite-stimulated eNOS-Thr(497) phosphorylation, thereby providing no conclusive evidence of a role for ROCK1/2. Knockdown of PKC-related protein kinase 1/2, another Rho effector, also did not reverse arsenite-stimulated eNOS-Thr(497) phosphorylation. In contrast, we found that transfection with an siRNA against citron Rho-interacting kinase (CRIK), the other downstream effector of Rho, significantly reversed the arsenite-induced eNOS-Thr(497) phosphorylation that was accompanied by restoration of eNOS enzymatic activity repressed by arsenite. Moreover, CRIK directly phosphorylated eNOS-Thr(497)in vitro. Finally, we also found that arsenite increased eNOS-Thr(497) phosphorylation and decreased acetylcholine-induced vessel relaxation in rat aortas. In conclusion, we demonstrate that arsenite acutely inhibits eNOS enzymatic activity and vessel relaxation in part by increasing the RhoA/CRIK/eNOS-Thr(497) phosphorylation signaling axis, which provides a molecular mechanism underlying arsenite-induced impaired vascular diseases.

Arsenite Acutely Decreases Nitric Oxide Production via the ROS-Protein Phosphatase 1-Endothelial Nitric Oxide Synthase-Thr(497) Signaling Cascade

Chronic (>24 h) exposure of arsenite, an environmental toxicant, has shown the decreased nitric oxide (NO) production in endothelial cells (EC) by decreasing endothelial NO synthase (eNOS) expression and/or its phosphorylation at serine 1179 (eNOS-Ser¹¹⁷⁹ in bovine sequence), which is associated with increased risk of vascular diseases. Here, we investigated the acute (<24 h) effect of arsenite on NO production using bovine aortic EC (BAEC). Arsenite acutely increased the phosphorylation of eNOS-Thr⁴⁹⁷, but not of eNOS-Ser¹¹⁶ or eNOS-Ser¹¹⁷⁹, which was accompanied by decreased NO production. The level of eNOS expression was unaltered under this condition. Treatment with arsenite also induced reactive oxygen species (ROS) production, and pretreatment with a ROS scavenger N-acetyl-L-cysteine (NAC) completely reversed the observed effect of arsenite on eNOS-Thr⁴⁹⁷ phosphorylation. Although protein kinase C (PKC) and protein phosphatase 1 (PP1) were reported to be involved in eNOS-Thr⁴⁹⁷ phosphorylation, treatment with PKC inhibitor, Ro318425, and overexpression of various PKC isoforms did not affect the arsenite-stimulated eNOS-Thr⁴⁹⁷ phosphorylation. In contrast, treatment with PP1 inhibitor, calyculin A, mimicked the observed effect of arsenite on eNOS-Thr⁴⁹⁷ phosphorylation. Lastly, we found decreased cellular PP1 activity in arsenite-treated cells, which was reversed by NAC. Overall, our study demonstrates firstly that arsenite acutely decreases NO production at least in part by increasing eNOS-Thr⁴⁹⁷ phosphorylation via ROS-PP1 signaling pathway, which provide the molecular mechanism underlying arsenite-induced increase in vascular disease.

Promoter methylation of p16, DAPK, CDH1, and TIMP-3 genes in cervical cancer: correlation with clinicopathologic characteristics

This study was conducted to investigate the promoter methylation status of the p16, DAPK, CDH1, and TIMP-3 genes in primary cervical cancer and its correlation with clinicopathologic characteristics. Promoter methylation was evaluated using a methylation-specific polymerase chain reaction in 78 cervical cancer tissue specimens and 24 control, normal cervical tissue specimens. Clinicopathologic parameters were obtained from medical records, and the relationship between the discrete variables and the methylation status was evaluated. The frequencies of promoter methylation of p16, DAPK, CDH1, and TIMP-3 in cervical cancer were 57%, 44.9%, 52.6%, and 9%, respectively. Primary cervical cancer had significantly higher methylation frequencies for the p16 and DAPK promoters than did the control, normal cervix (P < 0.0001). The promoter methylation of TIMP-3 was significantly higher in adenocarcinoma than in squamous cell carcinoma (41.7% vs 3%, respectively, P= 0.0175). High-stage cancers exhibited an increased promoter methylation frequency for p16 (P= 0.0061). The promoter methylation of the p16 gene is a frequent event in cervical carcinogenesis and may have potential clinical application as a marker for the progression and prognosis of cancer.

Non-traumatic peroneal nerve palsy: MRI findings

AIM

To present magnetic resonance imaging (MRI) findings of non-traumatic peroneal nerve palsy and to evaluate the usefulness of MRI in patients with non-traumatic peroneal nerve palsy.

MATERIALS AND METHODS

In a retrospective study, 11 consecutive patients presenting with peroneal nerve palsy were included. MR images of the lower leg and electrophysiological examinations were also reviewed. The cause of peroneal nerve palsy was determined on the basis of MRI findings and was evaluated using electrophysiological data. Nine patients with causative lesions detected on MRI, underwent surgery.

RESULTS

Clinical examination and electromyography (EMG) disclosed 11 peroneal lesions. MRI and EMG revealed three types of signal intensity change, i.e. deep peroneal nerve palsy type, common peroneal nerve palsy type, and superficial peroneal nerve palsy type. The MRI and EMG findings were in agreement in seven (65%) of the 11 study patients. In nine patients the causative lesions were identified using MRI, including ganglion cyst (n=6), osteochondroma (n=1), synovial cyst (n=1), and aneurysm (n=1).

CONCLUSION

Ganglion cyst is the most common cause of non-traumatic peroneal nerve palsy. MRI offers a noninvasive method for obtaining useful information to assess, localize, and monitor peripheral peroneal nerve palsy.

Hypoxia-induced endothelial NO synthase gene transcriptional activation is mediated through the tax-responsive element in endothelial cells

Although hypoxia is known to induce upregulation of endothelial NO synthase (eNOS) gene expression, the underlying mechanism is largely unclear. In this study, we show that hypoxia increases eNOS gene expression through the binding of phosphorylated cAMP-responsive element binding (CREB) protein (pCREB) to the eNOS gene promoter. Hypoxia (1% O2) increased both eNOS expression and NO production, peaking at 24 hours, in bovine aortic endothelial cells, and these increases were accompanied by increases in pCREB. Treatment with the protein kinase A inhibitor H-89 or transfection with dominant-negative inhibitor of CREB reversed the hypoxia-induced increases in eNOS expression and NO production, with concomitant inhibition of the phosphorylation of CREB induced by hypoxia, suggesting an involvement of protein kinase A/pCREB-mediated pathway. To map the regulatory elements of the eNOS gene responsible for pCREB binding under hypoxia, we constructed an eNOS gene promoter (-1600 to +22 nucleotides) fused with a luciferase reporter gene [pGL2-eNOS(-1600)]. Hypoxia (for 24-hour incubation) increased the promoter activity by 2.36+/-0.18-fold in the bovine aortic endothelial cells transfected with pGL2-eNOS(-1600). However, progressive 5'-deletion from -1600 to -873 completely attenuated the hypoxia-induced increase in promoter activity. Electrophoretic mobility shift, anti-pCREB antibody supershift, and site-specific mutation analyses showed that pCREB is bound to the Tax-responsive element (TRE) site, a cAMP-responsive element-like site, located at -924 to -921 of the eNOS promoter. Our data demonstrate that the interaction between pCREB and the Tax-responsive element site within the eNOS promoter may represent a novel mechanism for the mediation of hypoxia-stimulated eNOS gene expression.

Insufficiency fractures of the sternum

Insufficiency fractures occur within weakened bones that are unable to withstand the stress of every day normal activities. The spine, pelvis, and lower long-bone extremities are common sites of insufficiency fractures. Spontaneous sternal insufficiency fracture (SIF) has rarely been reported in elderly patients. To recognise a sternal insufficiency fracture is important in selecting the adequate diagnostic procedures.

Epithelioid hemangioma of bone

Epithelioid hemangioma of bone is a rare type of angiomatous tumor. We report a documented case of epithelioid hemangioma occurring in the distal femur of a 35-year-old man. The clinical, radiographic, MR imaging and histologic findings of the tumor are described. Radiographs showed a well-defined expanding, osteolytic lesion in the diaphysis of the femur. MR imaging showed the lesion to have low signal intensity on T1-weighted images and intermediate signal intensity on T2-weighted images. Grossly the lesion was multiloculated with a dark brown, jelly-like content. To characterize the imaging appearances of epithelioid hemangioma, we reviewed the available literature on the subject.

Myxoid liposarcoma: appearance at MR imaging with histologic correlation

Although myxoid liposarcoma is a subtype of liposarcoma, it may be difficult to establish the correct diagnosis with magnetic resonance (MR) imaging due to the lack of fat signal intensity. Without the administration of gadolinium contrast material, the tumor may even mimic a cystic tumor. A spectrum of MR imaging abnormalities occur in myxoid liposarcoma, depending on the amount of fat and myxoid material, the degree of cellularity and vascularity, and the presence of necrosis. Most myxoid liposarcomas have lacy or linear, amorphous foci of fat. Some myxoid liposarcomas appear to be cystic at nonenhanced MR imaging, although they enhance like other solid masses at contrast material-enhanced MR imaging. The enhancing areas within the tumor represent increased cellularity and vascularity; the nonenhancing areas represent necrosis, reduced cellularity, and accumulated mucinous material. Gadolinium-enhanced imaging is important in differentiating myxoid liposarcoma from benign cystic tumors. Characterization of the tumor with MR imaging plays an important role in the management of myxoid liposarcoma.

FES-biofeedback versus intensive pelvic floor muscle exercise for the prevention and treatment of genuine stress incontinence

We undertook this work to compare the treatment efficacies and the changes of quality of life after pelvic floor muscle (PFM) exercise and the functional electrical stimulation (FES)-biofeedback treatment, both of which are being widely used as conservative treatment methods for female urinary incontinence. We randomly selected 60 female incontinence patients who visited our department and divided them evenly into two groups. They were treated for a period of 6 weeks. The subjective changes in the severity of incontinence and discomfort in daily and social life were measured using a translated version of the questionnaire by Jackson. Objective changes of pelvic muscle contraction force were measured using a perineometer. Pre- and post-treatment maximal pelvic floor muscle contractile (PMC) pressure and changes in the severity of urinary incontinence and discomfort of the two groups showed statistically significant differences (p<0.001). In particular the FES-biofeedback group showed significantly increased maximal PMC pressure and a decreased severity of urinary incontinence and discomfort compared to the intensive PFM exercise group (p<0.001). In conclusion, FES-biofeedback proved more effective than simple PFM exercise.

The effect of pelvic floor muscle exercises on genuine stress incontinence among Korean women--focusing on its effects on the quality of life

This study's purpose was to compare the treatment efficacy and the effects on the patients' quality of life of the pelvic floor muscle (PFM) exercise and the functional electrical stimulation (FES)-biofeedback method. Ninety female incontinence patients were randomly selected and evenly divided into three groups: control, intensive PFM exercise, and FES-biofeedback groups. They were treated for 6 weeks. The subjective changes in the severity of incontinence and discomfort in daily and social life were measured using a translated version of Jackson's Bristol female urinary symptom questionnaire. Objective changes of pelvic muscle contraction force were measured by perineometer. Pre and post-treatment maximal pelvic floor muscle contractile pressure (PMC pressure) among the three groups showed statistically significant differences (p < 0.001). Especially the FES-biofeedback group showed significantly increased maximal PMC pressure compared with other groups (p < 0.001). From the questionnaire, pre and post-treatment changes in the severity of urinary incontinence and discomfort due to incontinence showed significant differences among the three groups (p < 0.001). The level of discomfort in daily life, social activity, physical activity, personal relations and discomfort due to urinary symptoms had largely changed and the FES-biofeedback group, in particular, showed a significant decrease after treatment. In conclusion, when PFM exercise and FES-biofeedback were compared in terms of their effects on the patients' quality of life, FES-biofeedback proved to be more effective than verbal explanation or simple PFM exercise.

A case of sternal insufficiency fracture

We report a case of insufficiency fracture of the sternum in a 70-year-old female patient with a review of the literature. She complained of sudden onset chest pain and aggravating dyspnea. She has been managed with corticosteroid due to chronic obstructive pulmonary disease for 15 years. Diagnosis of sternal insufficiency fracture presented with thoracic kyphosis was made on the basis of absence of trauma history, radiologic findings of lateral chest radiograph, bone scintigraphy and chest computed tomography. Thoracic kyphosis and osteoporosis secondary to menopause, corticosteroid therapy and limited mobility due to chronic obstructive pulmonary disease were considered as predisposing factors of the sternal insufficiency fracture in this patient.

Regional bone changes in deep soft tissue hemangiomas: radiographic and MR features

OBJECTIVE

To evaluate changes in bone adjacent to deep soft tissue hemangiomas of the extremities.

DESIGN AND PATIENTS

We retrospectively reviewed the plain films of 115 patients with histologically proven deep soft tissue hemangiomas of the extremities. The length and pattern of the bone changes were analyzed and correlated with the MRI examination (n = 55) and surgical findings.

RESULTS

Plain film studies demonstrated reactive bone changes adjacent to the deep soft tissue hemangiomas in 24 (21%) patients and phleboliths in 23 (20%) patients. The results of plain film analysis revealed a wide spectrum of regional bone changes adjacent to the hemangiomas, including periosteal reactions (16%), regional osteopenia (1%), cortical erosion (3%), bony overgrowth (3%), coarsening of the trabeculae (5%), and a combination of the above changes (4%). The length of the reactive changes corresponded approximately to the size of the hemangioma in 70% and was longer than the largest dimension of the hemangioma in 30%. Of the 55 patients studied with MRI, 39 (71%) patients had normal bones and 16 (29%) had bone changes.

CONCLUSION

Deep soft tissue hemangiomas may cause changes in adjacent bones. Familiarity with the pattern of reactive bone changes may help to avoid misdiagnosis.

The cytotoxicity of psoralidin from Psoralea corylifolia

A cytotoxic coumestan derivative, psoralidin (1), was isolated from the seed of Psoralea corylifolia. The IC50 values of 1 against SNU-1 and SNU-16 carcinoma cell lines were 53 and 203 micrograms/ml, respectively, indicating cytotoxic activity against stomach carcinoma cell lines.

Sequential changes of traumatic vertebral compression fracture on MR imaging

The purpose of this study was to evaluate the sequential signal intensity changes in post-traumatic vertebral compression fractures of varying ages. Sixty-six patients with 115 post-traumatic vertebral compression fractures underwent MR imaging. The ages of fractures at the time of MR images ranged from 1 day to 6 years. Sequential follow-up MR imagings were obtained in 4 patients for 2 years after initial MR examination. The fracture sites in all 52 fractures with traumatic events less than 3 months prior were hypointense on T1-weighted images and hyperintense on T2-weighted images (type I). A type I fracture could be subdivided into 3 patterns depending on its morphologic appearance: diffuse (type Ia); patchy (type Ib); and bandlike (type Ic). In 12 fractures of 3 to 5 months after trauma, six showed focal hypointensity (type II) in all pulse sequences, and six showed isointensity (type IV). Four of 51 fractures with trauma over 5 months showed focal hyperintensity on T1-weighted images and isointensity on T2-weighted images (type III); and the remaining 47 fractures showed isointensity on all sequences (type IV). In conclusion, MR imaging is useful in predicting the age of known traumatic compression fractures, so familiarity with these sequential MR findings would be helpful in distinguishing benign from malignant fractures.