Impaired residual renal function predicts denosumab-induced serum calcium decrement as well as increment of bone mineral density in non-severe renal insufficiency.

Denosumab treatment of osteoporotic patients, except those with severe renal insufficiency, reduced cCa levels. Low baseline cCa, low estimated glomerular filtration rate, and high bone turnover increased the risk of lower cCa, while increasing bone mineral density. Pretreatment with antiresorptive agents was beneficial in reducing the risk of hypocalcemia. INTRODUCTION: Although denosumab-induced hypocalcemia has been frequently observed in patients with chronic kidney disease (CKD) stages 4-5D being treated with denosumab for osteoporosis, few studies have assessed the risk factors for serum-corrected calcium (cCa) reductions in patients with non-severe renal insufficiency. This study assessed the risk factors for reduced cCa concentration following denosumab administration and analyzed factors predictive of changes in bone mineral density (BMD). METHODS: Seventy-seven osteoporotic patients, not including those with CKD stages 4-5D, were treated with 60 mg denosumab once every 6 months. Biochemical parameters and BMD were analyzed from prior to the initial dose until 1 month after the second dose. RESULTS: Following the first administration of denosumab, cCa levels decreased, reaching a minimum on day 7. Multiple linear regression analyses showed that baseline cCa, estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2, tartrate-resistant acid phosphatase-5b (TRACP-5b), and bone alkaline phosphatase (BAP) or pretreatment with antiresorptive agents were significant factors independently associated with the absolute reduction in cCa from baseline to day 7 (ΔcCa0-7 days). ΔcCa0-7 days after the second dose of denosumab was significantly lower than that after the first dose. After 6 months of denosumab treatment, both LS-BMD and FN-BMD significantly increased from baseline. LS-BMD and FN-BMD correlated significantly with baseline TRACP-5b or BAP and eGFR, respectively. CONCLUSIONS: Both low eGFR and high bone turnover were independent risk factors for denosumab-induced cCa decrement, and for increases in BMD. Pretreatment with antiresorptive agents may reduce the risk of hypocalcemia.

Increased undercarboxylated osteocalcin/intact osteocalcin ratio in patients undergoing hemodialysis.

UNLABELLED: Serum undercarboxylated osteocalcin (ucOC)/intact osteocalcin (iOC) ratio increased >1.0 in the patients undergoing hemodialysis, particularly in those with high bone turnover state. Consequently, serum ucOC/iOC ratio might lose its significance as a bone metabolic marker to indicate vitamin K deficiency in hemodialysis patients. INTRODUCTION: Serum intact osteocalcin (iOC), undercarboxylated OC (ucOC), and the ucOC/iOC ratio are considered clinically relevant indices in pre-dialysis chronic kidney disease (CKD) and hemodialysis (HD) patients, despite their accumulation in uremic serum. METHODS: Serum iOC and ucOC were measured along with serum intact parathyroid hormone (iPTH), bone alkaline phosphatase (BAP), and tartrate-resistant acid phosphatase (TRACP)-5b in 89 pre-dialysis CKD and 189 HD patients. RESULTS: Serum iOC and ucOC showed significantly negative correlations with estimated glomerular filtration rate in pre-dialysis CKD patients, although serum ucOC/iOC ratio did not correlate. Serum ucOC was significantly greater in HD patients than in pre-dialysis CKD patients, while serum iOC did not differ significantly, resulting in serum ucOC/iOC ratio >1.0 in 135 (71.4%) out of 189 HD patients. HD patients with high serum ucOC/iOC ratio (>1.0) had a significantly younger age and significantly higher values of body mass index, serum creatinine, albumin, phosphate, iPTH, and TRACP-5b than those with low ucOC/iOC ratio (≤ 1.0). The baseline iPTH and P1NP correlated with the changes of the ucOC/iOC ratio during the 2 days of the inter-dialytic period. Multivariate analysis showed that log [ucOC/iOC] in HD patients was significantly associated with log [iPTH], log [BAP], or log [TRACP-5b]. CONCLUSIONS: Serum ucOC/iOC ratio >1.0 was observed in as high as 71.4% of HD patients, preferentially with high bone turnover state, in comparison with pre-dialysis CKD patients. These data suggested that serum ucOC/iOC ratio might lose its significance as a bone metabolic marker to indicate vitamin K deficiency in HD patients.

Decreased cortical thickness, as estimated by a newly developed ultrasound device, as a risk for vertebral fracture in type 2 diabetes mellitus patients with eGFR of less than 60 mL/min/1.73 m2.

UNLABELLED: Cortical porosity is increasingly recognized as an important risk for fracture in DM patients. The present study demonstrated that decreased cortical thickness, assessed using a newly developed quantitative ultrasonic bone densitometry, is a significant risk factor for vertebral fractures in type 2 diabetes mellitus patients with stage 3 or higher chronic kidney disease, but not in those without. INTRODUCTION: Cortical porosity is increasingly recognized as an important risk factor for fracture in type 2 diabetes mellitus (T2DM) patients as well as in stage 3 chronic kidney disease (CKD) patients in whom serum parathyroid hormone (PTH) starts to increase. The present study aimed to clarify whether the coexistence of CKD might affect the relationship of decreased cortical thickness (CoTh) in the development of vertebral fractures (VF) in T2DM patients. METHODS: In this cross-sectional study, trabecular bone mineral density (TrBMD), elastic modulus of trabecular bone (EMTb), and CoTh were estimated with a new quantitative ultrasound bone densitometry in 173 T2DM patients. VFs were identified radiographically. RESULTS: Thirty-nine patients (22.5%) had VF. Those with estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2) (low eGFR) showed a significantly higher VF rate (32.4%) than those with eGFR ≥60 mL/min/1.73 m(2) (high eGFR, 16.2%). Serum PTH was significantly higher with low eGFR than with high eGFR. In those with high eGFR, EMTb was significantly lower in VF(+) than VF(-). In those with low eGFR, TrBMD, EMTb, and CoTh were significantly lower in VF(+) than in VF(-). In a multivariate logistic regression analysis, EMTb was independently and significantly associated with VF in T2DM patients with a high eGFR, in contrast to those with only CoTh with VF in T2DM with low eGFR. CONCLUSION: This study demonstrated CoTh as a factor independently associated with VF in T2DM patients with low eGFR and increasing serum PTH levels.

Increased active PTH(1-84) fraction as a predictor of poor mortality in male hemodialysis patients.

UNLABELLED: We reported previously that serum parathyroid hormone [PTH(1-84)]/intact PTH[PTH(1-84) + PTH(7-84)] ratio provides the better marker for parathyroid function and bone turnover state than serum PTH level itself. The present study demonstrated that higher PTH(1-84)/intact PTH ratio, but not serum PTH(1-84) and intact PTH, predicted higher all-cause mortality in 177 male hemodialysis patients. INTRODUCTION: We reported that PTH(1-84)/intact PTH ratio provides a clinically relevant marker for parathyroid function and the resultant bone turnover state. The purpose of our study was to investigate the association of PTH(1-84)/intact PTH ratio with all-cause mortality (ACM) in male hemodialysis patients. METHODS: The study was performed for 70 months. Serum PTH in 177 male hemodialysis patients was measured with PTH(1-84)-specific whole PTH assay and intact PTH assay which cross-reacts with N-truncated PTH including PTH(7-84). RESULTS: The patients (n = 177) were divided into higher and lower halves based on serum levels of PTH(1-84)/intact PTH ratio (cutoff value, 0.484), intact PTH (143.8 pg/mL), and PTH(1-84) (64.1 pg/mL). In Kaplan-Meier analysis, the higher group in whole PTH/intact PTH ratio had significantly higher ACM than the lower group (P = 0.020 by log-rank test), in contrast with the insignificant difference between the higher and lower groups in intact PTH and PTH(1-84). Multivariate Cox regression hazard analysis identified higher log [PTH(1-84)/intact PTH ratio], but not log intact PTH or log PTH(1-84) as a significant independent predictor [hazard ratio 14.428 (95% CI 2.486-83.728)] for ACM after adjustment for various factors including age, hemodialysis duration, presence/absence of diabetes mellitus, BMI, log C-reactive protein, serum albumin, calcium, and phosphate. The association existed between log [PTH(1-84)/intact PTH ratio] and ACM in those without vitamin D administration (n = 95). CONCLUSION: Higher PTH(1-84)/intact PTH ratio, which provides a relevant marker for parathyroid function, may be a significant predictor of ACM in male hemodialysis patients.

Reduction of whole PTH/intact PTH ratio as a predictor of bone metabolism in cinacalcet treatment of hemodialysis patients with secondary hyperparathyroidism.

UNLABELLED: In cinacalcet treatment of hemodialysis (HD) patients with secondary hyperparathyroidism (SHPT), not only intact parathyroid hormone (I-PTH), whole PTH (W-PTH), and bone markers, but also W-PTH/I-PTH ratio as proportion of active PTH(1-84) molecules were decreased. Changes in W-PTH/I-PTH ratio significantly correlated and predicted changes in bone marker. INTRODUCTION: Cinacalcet partly suppresses the secretion of PTH by enhancing PTH(1-84) degradation into N-truncated fragments. The objectives of this study is to investigate the significance of the N-truncated PTH/PTH(1-84) ratio for the prediction of the effect of cinacalcet in HD patients. METHODS: Serum parameters were measured during 12 weeks of oral cinacalcet administration at 25 mg daily in 39 HD patients with SHPT. RESULTS: Serum Ca, Pi, W-PTH, I-PTH, and W-PTH/I-PTH ratio all decreased significantly in a time-dependent manner during cinacalcet administration. Serum tartrate-resistant acid phosphatase (TRAP) 5b reflected these changes more precisely than serum N-telopeptide of type-I collagen. At 1 week, changes in I-PTH and W-PTH correlated significantly with those in serum Pi, but not Ca. Changes in serum Pi (but not Ca) and serum W-PTH also correlated significantly with changes in serum TRAP5b at both 4 and 12 weeks, while changes in serum I-PTH correlated significantly with those in serum TRAP5b only at 12 weeks. Changes in the serum W-PTH/I-PTH ratio correlated significantly with those in serum TRAP5b at both 4 and 12 weeks, and changes in serum W-PTH/I-PTH ratio at 4 weeks showed a tendency for a correlation with changes in serum TRAP5b at 12 weeks. HD patients with a reduced W-PTH/I-PTH ratio after 4 weeks had a significantly greater reduction of TRAP5b over 12 weeks. CONCLUSION: W-PTH and the W-PTH/I-PTH ratio allow estimation of the potency of cinacalcet in enhancement of PTH degradation, and thus no less reliable markers than I-PTH for reflecting cinacalcet-induced bone resorption.

Add-on combination therapy with adefovir dipivoxil induces renal impairment in patients with lamivudine-refractory hepatitis B virus.

Combination therapy with adefovir dipivoxil (ADV) and lamivudine (LAM) is recommended for patients infected with LAM-refractory hepatitis B virus (HBV). However, the effects of such therapy on renal function and serum phosphorus levels have not been fully evaluated. Combination therapy with ADV and LAM was given to 37 patients infected with LAM-refractory HBV, including 17 with hepatic cirrhosis. Serum HBV DNA levels decreased to below 2.6 log(10) copies/mL in 23 (62%) of 37 patients at 12 months, 25 (78%) of 32 patients at 24 months, and 16 (84%) of 19 patients at 36 months. Except for one cirrhotic patient, serum alanine aminotransferase levels were below 50 IU/L in all patients during combination therapy. Serum creatinine levels increased in 14 (38%) of 37 patients, and serum phosphate levels decreased to below 2.5 mg/mL in 6 (16%) of 37 patients during combination therapy. Patients who received combination therapy for 36 months or longer had a significantly incidence of elevated serum creatinine levels. Fanconi syndrome occurred in a 57-year-old woman with cirrhosis after ADV was added to LAM. Combination therapy with ADV and LAM can maintain biochemical remission in patients with LAM-refractory HBV. However, the dosing interval of ADV should be adjusted according to renal function and serum phosphate levels in patients receiving long-term treatment.

Poor muscle quality rather than reduced lean body mass is responsible for the lower serum creatinine level in hemodialysis patients with diabetes mellitus.

BACKGROUND: The serum creatinine level is significantly lower in well-nourished hemodialysis patients with diabetes mellitus (DM) than in their non-DM counterparts, despite the presence of anuria in these patients. The factors associated with this finding have not been determined. PATIENTS AND METHODS: We evaluated the association of serum creatinine with handgrip strength (HGS) and lean body mass index (LMI) in a cross-sectional study of 102 DM and 208 non-DM hemodialysis patients to determine if poorer muscle quality in DM patients could explain the reduced level of serum creatinine. All the DM patients were well-nourished. Grip dynamometry and dual-energy X-ray absorptiometry (DXA) were used to measure HGS and LMI, respectively. RESULTS: The DM patients had a significantly lower serum creatinine level and HGS compared to the non-DM patients, but whole-body LMI and LMI of the upper limbs did not differ between the two groups of patients. The DM patients had significantly lower serum creatinine/whole-body LMI, serum creatinine/arm LMI, HGS/whole-body LMI, and HGS/arm LMI ratios. The serum creatinine level was significantly correlated with HGS and with whole-body and upper limb LMI in both groups of patients. However, regression analyses of LMI with serum creatinine and HGS gave significantly shallower slopes for the DM patients compared to the non-DM patients. CONCLUSION: This suggests that the muscle strength generated per unit of muscle mass, which is reflected well by the serum creatinine level, is significantly reduced in DM hemodialysis patients. Therefore, our results show that the significantly lower serum creatinine levels in DM hemodialysis patients compared to non-DM hemodialysis patients may be explained by poor muscle quality rather than by reduced muscle mass or malnutrition.

Hemoglobin aggregation in single red blood cells of sickle cell anemia.

A laser light scattering technique was used to observe the extent of hemoglobin aggregation in solitary red blood cells of sickle cell anemia. Hemoglobin aggregation was confirmed in deoxygenated cells. The light scattering technique can also be applied to cytoplasmic studies of any biological cell.

Neuropilin-1 promotes human glioma progression through potentiating the activity of the HGF/SF autocrine pathway.

Neuropilin-1 (NRP1) functions as a coreceptor through interaction with plexin A1 or vascular endothelial growth factor (VEGF) receptor during neuronal development and angiogenesis. NRP1 potentiates the signaling pathways stimulated by semaphorin 3A and VEGF-A in neuronal and endothelial cells, respectively. In this study, we investigate the role of tumor cell-expressed NRP1 in glioma progression. Analyses of human glioma specimens (WHO grade I-IV tumors) revealed a significant correlation of NRP1 expression with glioma progression. In tumor xenografts, overexpression of NRP1 by U87MG gliomas strongly promoted tumor growth and angiogenesis. Overexpression of NRP1 by U87MG cells stimulated cell survival through the enhancement of autocrine hepatocyte growth factor/scatter factor (HGF/SF)/c-Met signaling. NRP1 not only potentiated the activity of endogenous HGF/SF on glioma cell survival but also enhanced HGF/SF-promoted cell proliferation. Inhibition of HGF/SF, c-Met and NRP1 abrogated NRP1-potentiated autocrine HGF/SF stimulation. Furthermore, increased phosphorylation of c-Met correlated with glioma progression in human glioma biopsies in which NRP1 is upregulated and in U87MG NRP1-overexpressing tumors. Together, these data suggest that tumor cell-expressed NRP1 promotes glioma progression through potentiating the activity of the HGF/SF autocrine c-Met signaling pathway, in addition to enhancing angiogenesis, suggesting a novel mechanism of NRP1 in promoting human glioma progression.

Primary hyperparathyroidism caused by parathyroid-targeted overexpression of cyclin D1 in transgenic mice.

The relationship between abnormal cell proliferation and aberrant control of hormonal secretion is a fundamental and poorly understood issue in endocrine cell neoplasia. Transgenic mice with parathyroid-targeted overexpression of the cyclin D1 oncogene, modeling a gene rearrangement found in human tumors, were created to determine whether a primary defect in this cell-cycle regulator can cause an abnormal relationship between serum calcium and parathyroid hormone response, as is typical of human primary hyperparathyroidism. We also sought to develop an animal model of hyperparathyroidism and to examine directly cyclin D1's role in parathyroid tumorigenesis. Parathyroid hormone gene regulatory region--cyclin D1 (PTH--cyclin D1) mice not only developed abnormal parathyroid cell proliferation, but also developed chronic biochemical hyperparathyroidism with characteristic abnormalities in bone and, notably, a shift in the relationship between serum calcium and PTH. Thus, this animal model of human primary hyperparathyroidism provides direct experimental evidence that overexpression of the cyclin D1 oncogene can drive excessive parathyroid cell proliferation and that this proliferative defect need not occur solely as a downstream consequence of a defect in parathyroid hormone secretory control by serum calcium, as had been hypothesized. Instead, primary deregulation of cell-growth pathways can cause both the hypercellularity and abnormal control of hormonal secretion that are almost inevitably linked together in this common disorder.

Enzyme modification by polymers with solubilities that change in response to photoirradiation in organic media.

We have synthesized a hybrid subtilisin the solubility of which can be regulated by photoirradiation through coupling with a photoresponsive copolymer that carries spiropyran groups in its side chains. The copolymer was synthesized by polymerization of methacrylate, methacrylic acid, and spiropyran-carrying methacrylate. It was then covalently bonded to the amino groups of subtilisin Carlsberg via its carboxyl groups using a carbodiimide coupling agent. The hybrid subtilisin was perfectly soluble in toluene and efficiently catalyzed transesterification. After ultraviolet irradiation, the hybrid subtilisin precipitated and was easily and quantitatively recovered by centrifugation. Recovered hybrid subtilisin, resolubilized by visible light irradiation, retained its original transesterification activity even after several cycles of precipitation and solubilization.

Influences of Pre-formed Donor-Specific Anti-Human Leukocyte Antigen Antibodies in Living-Donor Renal Transplantation: Results With Graft Immunocomplex Capture Fluorescence Analysis.

BACKGROUND: Advances in immunosuppressants enable organ transplantation for sensitized patients. However, influences of pre-formed donor-specific anti-human leukocyte antigen (HLA) antibodies (DSA) have not been fully understood in renal transplantation (RT). On the other hand, immunocomplex capture fluorescence analysis (ICFA) is a reliable method to detect donor-specific anti-HLA antibodies and HLA antigen complexes. Graft ICFA can detect DSA in an allograft (g-DSA). METHODS: To elucidate the consequences of pre-formed DSA, 198 patients who underwent living-donor RT were enrolled for this study (observation period: 57.8 ± 34.9 months); 187 patients in the DSA- group (excluding ABO-incompatible cases) and 11 patients in the DSA+ group. Before RT, all DSA+ patients had undergone rituximab administration and plasmapheresis. For a graft ICFA, the biopsy specimen (1 × 105 cells) was dissolved, and HLA antigens were captured by anti-HLA beads. Finally, DSA-HLA complexes were detected by means of PE-conjugated anti-human IgG antibodies and analyzed by use of a Luminex system. A ratio (sample/blank beads, mean of fluorescence intensity) was calculated: ≥1.0 was determined as positive g-DSA. RESULTS: There were no significant differences in 5-year graft survival (87.9%/100% in the DSA-/DSA+ groups, respectively). In terms of antibody-mediated rejection (AMR), within 1 month after RT, pathologically determined AMR occurred 3.2% and 63.4% in the DSA- and DSA+ groups, respectively (P < .0001). However, interestingly, more than half of them (57.1%) indicated only subclinical AMR, that is, no fluctuation of S-Cr. As representative of 2 cases of subclinical AMR, g-DSA deposition could be confirmed (1.15 ± 0.04) at 1 hour after reperfusion by graft ICFA. Furthermore, g-DSA shifted to 2.20 ± 0.98 at 3 weeks after transplantation, along with a decline in s-DSA mean of fluorescence intensity (1718-506.5). CONCLUSIONS: Although pathologically determined AMR occurred more frequently in pre-formed DSA+ recipients, it can be argued that a successful de-sensitization protocol inhibits further production of DSA and graft destruction.

Orientation and aggregation of hydrophobic helical peptides in phospholipid bilayer membrane.

Hydrophobic sequential peptides with various chain lengths, Boc-(Ala-Aib)n-OMe (n = 2, 4, 6, 8) and Boc-Ser(CH2Ant)-(Ala-Aib)n-OMe (n = 2, 4, 6, 8, 10, Ant represents O-anthrylmethyl; abbreviated as A2-A10), were synthesized and their orientation and aggregation in a lipid bilayer membrane were investigated. Circular dichroism (CD) measurements revealed that the peptides took a partially helical structure, and that the helix content increased with increasing chain length and upon distribution to phospholipid vesicles. When long-chain peptides, A8 and A10, were incorporated into lipid bilayer membranes, the membrane fluidity was reduced, while 5/6-carboxyfluorescein (CF) leakage through the bilayer membranes was enhanced. Fluorescence quenching of the anthracene group with 12-doxylstearic acid suggested that these peptides took a perpendicular orientation in the membrane. Detection of excimer emission and large fluorescence depolarization of the peptides indicated an aggregation in the membrane. In addition, Boc-(Ala-Aib)n-OMe (n = 4, 8) showed a channel-like activity in a bilayer lipid membrane (BLM). The channel-forming ability of the hexadecapeptide was higher than that of the octapeptide. Taken together, the long-chain hydrophobic helical peptides tend to aggregate in lipid bilayer membranes with a transmembrane orientation.

Orientation change of glycopeptide in lipid bilayer membrane induced by lectin binding.

A lectin-induced orientation change of a helical glycopeptide in lipid bilayer membranes was studied. Glycopeptides composed of hydrophobic nona-(G8) and pentapeptide (G4) with a fluorescent probe at the N-terminal and a lactose unit at the C-terminal were synthesized. The glycopeptides were incorporated into lipid bilayer membranes with the lactose unit exposed to the aqueous phase and the peptide chain buried in the membrane. G8 takes a partially helical structure in the membrane, while G4 an irregular structure. Upon binding of lectin to G8 held in the membrane of DPPC liposome, enhancement of fluorescence intensity of the N-terminal anthryl group, reduction of fluorescence quenching of the anthryl group with acrylamide, and increase of CF-leakage from the DPPC liposome were observed. G8', which lacks the O-anthryrlmethylserine residue from G8, formed a voltage-dependent ion channel in BLM experiments. The frequency of single current fluctuations induced by G8' incorporation increased with addition of lectin. These results indicate that the peptide segment of G8 prefers taking a more perpendicular orientation to the membrane upon association with lectin.

Self-assembly of mastoparan X derivative having fluorescence probe in lipid bilayer membrane.

A mastoparan X (MPX) derivative having an anthryl group at the C-terminal residue was synthesized (MPX-A), and its conformation, orientation and aggregation in phospholipid bilayer membrane were studied. The efficiency of intramolecular energy transfer from the Trp residue to the anthryl group at high peptide dilution suggested alpha-helical conformation in the lipid membrane, which is consistent with the previous report by NMR of MPX concentrated in the membrane. Either emission from the Trp residue or the anthryl group of MPX-A in the lipid membrane was quenched by 5-doxylstearic acid, suggesting that MPX-A is located at the membrane surface with the helix axis oriented parallel to the surface. The dependence of the excited energy transfer and the fluorescence depolarization of MPX-A on the peptide concentration revealed that MPX-A aggregated in the lipid membrane to form a defined structure.

Interaction of melittin derivatives with lipid bilayer membrane. Role of basic residues at the C-terminal and their replacement with lactose.

Melittin possesses an amphiphilic property in the primary sequence in which hydrophilic residues are located at the C-terminal region from Lys-21 to Gln-26. A part of the hydrophilic sequence was cleaved off by endopeptidase Arg-C to obtain melittin 1-22. The affinity of melittin 1-22 for neutral phospholipid membrane was reduced to 1/3 that of melittin, indicating that the basic residues, Lys-23 and Arg-24, are important in binding of melittin to the membrane. The melittin 1-22 was extended toward the C-terminal end by connection of lactose (melittin-lac), the membrane affinity of which was slightly higher than the melittin 1-22, but lower than melittin. The leakage experiment of 5,6-carboxyfluorescein encapsulated in DPPC liposomes showed that the activities of melittin 1-22 and melittin-lac in membrane lysis were much lower than melittin. However, the melittin 1-22 formed a voltage-dependent ion-channel in an azolectin bilayer membrane. It is thus considered that Lys-23 and Arg-24 residues of melittin play an important role in binding to the polar region of membrane for lysis, but not for ion-channel formation.

Photo-immobilization of epidermal growth factor enhances its mitogenic effect by artificial juxtacrine signaling.

Photo-reactive epidermal growth factor (EGF) was synthesized by coupling EGF with azidobenzoic acid and was immobilized onto the wells of a polystyrene culture plate by photo-irradiation. The photo-immobilized EGF enhanced the growth of anchorage-dependent cells more than native or azidobenzoyl derivatized EGF. A small amount of photo-immobilized EGF was sufficient to enhance the growth of cells and the maximal mitogenic effect was greater than that of native or derivatized EGF. On the other hand, the photo-immobilized EGF did not enhance growth of anchorage-independent cells. In addition, signal transduction in the cells adhered only on the EGF-immobilized surface was observed by staining of phosphotyrosine residues by anti-phosphotyrosine antibodies. These results showed that the enhanced cell growth was due to direct interaction between the cells and the immobilized EGF. Photo-immobilization could be a universal means of fixing growth factors onto an artificial matrix that is devoid of chemically functional groups scaffolding growth factors and could provide a new tool to elucidate signal transduction mechanism and could lead to the development of a new protein-free cell culture system or tissue engineering materials.

Receptor affinity of neurotensin message segment immobilized on liposome.

Neurotensin derivatives having a dioctadecyl group were synthesized and immobilized on DMPC liposome to construct a multivalent-ligand system. The derivatives are Ac-Glu[N(C18H37)2]-(Sar-Sar-Pro)n-Arg-Arg-Pro-Tyr-Ile-Leu-OH (D3nNT, n = 0,1,2,3), where a dioctadecyl group was connected to the N-terminal side of neurotensin 8-13 fragment directly or through a hydrophilic and flexible spacer chain of different lengths. The derivatives were spontaneously immobilized on DMPC liposome upon incubation overnight. The receptor affinity of the derivatives increased significantly upon immobilization on liposome. The maximum affinity was obtained by D9NT immobilized on DMPC liposome at the molar ratio of DMPC and D9NT of 200. This affinity is slightly better than the neurotensin 8-13 fragment, the message segment of the derivatives. The fluorescent microscopy using rhodamine-labelled liposome revealed that the multivalent-ligand system binds to specific receptors without dissociation of the derivative from DMPC liposome.

Fusion of liposomes due to transient and lasting perturbation induced by synthetic amphiphilic peptides.

The membrane-fusion activities of amphiphilic peptides of H-(Leu-Aib-Lys-Aib-Aib-Lys-Aib)n-Ala-N(C18H37)2 (n = 1, P7D and n = 3, P21D) immobilized on liposome were investigated. P7D, which takes a random conformation, induced fusion of DPPC SUV, but P7D immobilized on the DPPC SUV did not show the fusion activity. On the other hand, P21D showed a high activity of membrane fusion either in the free peptide or in the immobilized state. CF-Leakage experiments revealed that the peptides caused a transient perturbation of the membrane structure on binding to the membrane. A lasting and steady perturbation was also caused by P21D embedded in the membrane, which was indicated by EU3+ permeation through the membrane. This type of membrane perturbation was very slight in the case of P7D embedded in the membrane. A conclusion was reached that the different activities in the membrane fusion are based on the transient perturbation in the membrane at the peptide binding to the membrane surface as well as the steady perturbation caused by the peptide embedded in the membrane.