Effects of porcine 25 kDa amelogenin and its proteolytic derivatives on bone sialoprotein expression.

BACKGROUND AND OBJECTIVE: Amelogenins are hydrophobic proteins that are the major component of developing enamel. Enamel matrix derivative has been used for periodontal regeneration. Bone sialoprotein is an early phenotypic marker of osteoblast differentiation. In this study, we examined the ability of porcine amelogenins to regulate bone sialoprotein transcription. MATERIAL AND METHODS: To determine the molecular basis of the transcriptional regulation of the bone sialoprotein gene by amelogenins, we conducted northern hybridization, transient transfection analyses and gel mobility shift assays using the osteoblast-like ROS 17/2.8 cells. RESULTS: Amelogenins (100 ng/mL) up-regulated bone sialoprotein mRNA at 3 h, with maximal mRNA expression occurring at 12 h (25 and 20 kDa) and 6 h (13 and 6 kDa). Amelogenins (100 ng/mL, 12 h) increased luciferase activities in pLUC3 (nucleotides -116 to +60), and 6 kDa amelogenin up-regulated pLUC4 (nucleotides -425 to +60) activity. The tyrosine kinase inhibitor inhibited amelogenin-induced luciferase activities, whereas the protein kinase A inhibitor abolished 25 kDa amelogenin-induced bone sialoprotein transcription. The effects of amelogenins were abrogated by 2-bp mutations in the fibroblast growth factor 2 response element (FRE). Gel-shift assays with radiolabeled FRE, homeodomain-protein binding site (HOX) and transforming growth factor-beta1 activation element (TAE) double-strand oligonucleotides revealed increased binding of nuclear proteins from amelogenin-stimulated ROS 17/2.8 cells at 3 h (25 and 13 kDa) and 6 h (20 and 6 kDa). CONCLUSION: These results demonstrate that porcine 25 kDa amelogenin and its proteolytic derivatives stimulate bone sialoprotein transcription by targeting FRE, HOX and TAE in the bone sialoprotein gene promoter, and that full-length amelogenin and amelogenin cleavage products are able to regulate bone sialoprotein transcription via different signaling pathways.

Nicotine suppresses bone sialoprotein gene expression.

BACKGROUND AND OBJECTIVE: Tobacco smoking is a risk factor for periodontitis and osteoporosis. Nicotine is a major component of tobacco, and has been reported to inhibit proliferation and differentiation of osteoblasts. Bone sialoprotein (BSP) is a mineralized tissue-specific protein expressed by differentiated osteoblasts that appears to function in the initial mineralization of bone. The purpose of this study was to determine the effects of nicotine on bone metabolism. MATERIAL AND METHODS: We used rat osteobast-like UMR106 and ROS 17/2.8 cells and rat stromal bone marrow RBMC-D8 cells. To determine the molecular basis of the transcriptional regulation of the BSP gene by nicotine, we conducted Northern hybridization, transient transfection analyses with chimeric constructs of the BSP gene promoter linked to a luciferase reporter gene and gel mobility shift assays. RESULTS: Nicotine (250 microg/mL) decreased the BSP mRNA levels at 12 and 24 h in UMR106 and ROS 17/2.8 cells. From transient transfection assays using various sized BSP promoter-luciferase constructs, nicotine decreased the luciferase activities of the construct, including the promoter sequence nucleotides -116 to +60, in UMR106 and RBMC-D8 cells. Nicotine decreased the nuclear protein binding to the cAMP response element (CRE), fibroblast growth factor 2 response element (FRE) and homeodomain protein-binding site (HOX) at 12 and 24 h. CONCLUSION: This study indicates that nicotine suppresses BSP transcription mediated through CRE, FRE and HOX elements in the proximal promoter of the rat BSP gene.

Changes in waveform of congenital nystagmus associated with biofeedback treatment.

A study was made of parameters of congenital nystagmus which responded to auditory biofeedback treatment. The parameters studied included foveation time, amplitude, and frequency. The patient's right retina was observed with an infrared television fundus camera, and the fundus image was recorded on video tape. The position of the eye during nystagmus, observed via the fundus camera and recorded on video, was analysed at every 1/60 second intervals. The displacement in degrees between the fixation target, projected on to the retina, and the foveola was measured for each interval. Using biofeedback, the subjects could voluntarily suppress nystagmus and prolong foveation time. A damping of the nystagmus amplitude, intensity, and frequency was observed. On the average the intensity decreased by about 40%, and the foveation time was prolonged by about 190%. After completion of the training all the patients reported a subjective improvement in their vision when suppressing their nystagmus. Possibly biofeedback training acts to reduce the nystagmus and extend foveation time, thereby improving the ability to fixate.

[Lipoprotein (a) and sclerotic changes in retinal arterioles].

Lipoprotein (a) (Lp(a)) has been considered an independent risk factor for arteriosclerotic disease and its role in retinal vascular changes was studied in this report. The study was made on 160 patients of age 54 and above. They were divided into four groups depending upon their clinical background with or without the presence of diabetes mellitus (DM) and cerebral infarction (CI). The retinal vascular status of the patients was studied by ophthalmoscopic examination and the findings were graded according to Scheie's classification. We found that all the patients with retinal arterial hypertension and arteriosclerosis had a significant by high level of serum Lp (a). Similarly, serum Lp (a) level was higher in the patients with DM and CI than in the control subjects. These findings suggested that Lp (a) might influence the pathological changes of senile retinal arterioles. Moreover, we found a positive linear correlation between Lp (a) and plasminogen in patients with CI.