Glycation and phosphorylation of alpha-lactalbumin by dry heating: effect on protein structure and physiological functions

Alpha-lactalbumin (alpha-LA) was glycated with maltopentaose (MP) through the Maillard reaction (MP-alpha-LA) and subsequently phosphorylated by dry heating in the presence of pyrophosphate to investigate its structure and physiological functions. Glycation occurred effectively, and the sugar content of alpha-LA increased by approximately 22.3% through the Maillard reaction. The phosphorylation of MP-alpha-LA was enhanced with an increase in the dry-heating time from 1 to 5 d, and the phosphorous content of MP-alpha-LA increased by approximately 1.01% by dry heating at pH 4.0 and 85 degrees C for 5 d in the presence of pyrophosphate. The electrophoretic mobility of alpha-LA increased with an increase in the phosphorylation level. The circular dichroism spectra showed that the change in the secondary structure of the alpha-LA molecule by glycation and subsequent phosphorylation was slight. However, the Trp fluorescence intensity was increased by phosphorylation after glycation. In addition, the differential scanning calorimetry thermograms of alpha-LA showed that the denaturation temperature of MP-alpha-LA was decreased by phosphorylation. These results indicated that molten (partially unfolded) conformations of alpha-LA were formed by dry heating in the presence of pyrophosphate after glycation. The anti-alpha-LA antibody response was significantly reduced by glycation and subsequent phosphorylation. The suppressive effect of alpha-LA on the production of proinflammatory cytokines such as IL-6 and tumor necrosis factor-alpha from THP-1 cells after stimulation with lipopolysaccharide was significantly enhanced by glycation with MP and was further enhanced by phosphorylation after glycation. The Ca phosphate-solubilizing ability of alpha-LA was enhanced by phosphorylation. The apoptotic activity of alpha-LA was reduced by glycation and subsequent phosphorylation. These results suggest that phosphorylation by dry heating in the presence of pyrophosphate after glycation with MP through the Maillard reaction is a useful method for improvement of the physiological functions of alpha-LA.

Role of interleukin-1beta and tumor necrosis factor-alpha-dependent expression of cyclooxygenase-2 mRNA in thermal hyperalgesia induced by chronic inflammation in mice

The present study investigated whether the endogenous pro-inflammatory cytokines [interleukin (IL)-1beta and tumor necrosis factor-alpha (TNF-alpha)]-dependent expression of cyclooxygenase-2 (COX-2) mRNA within the spinal cord could be involved in the development of chronic inflammatory pain-like behaviors in mice. We demonstrated that the expression of COX-2 mRNA on the ipsilateral side of the spinal cord was significantly increased 6 h and 3 days after intraplantar injection of complete Freund's adjuvant (CFA), compared with the expression in saline-treated mice. In addition, the chronic pain-like behaviors following CFA injection were markedly suppressed by repeated intrathecal (i.t.) pre-treatment with the COX-2 inhibitor etodolac, but not with the COX-1 inhibitor mofezolac. The cytosolic level of the activated form of nuclear factor-kappa B (NF-kappaB), which is a major contributor to the induction of COX-2, on the ipsilateral side of the mouse spinal cord was also increased compared with that in the saline-treated mice. The key finding in the present study was that a single i.t. injection with either IL-1beta or TNF-alpha induced a marked increase in spinal COX-2 mRNA and persistent thermal hyperalgesia in mice. Furthermore, CFA-induced hypersensitivity to inflammatory pain was significantly reduced by repeated i.t. pre-injection of the recombinant Fc chimera of IL-1 receptor I or soluble TNF receptor I, which sequesters endogenous IL-1beta or TNF-alpha, respectively. In contrast, the expression of spinal COX-2 mRNA in CFA-treated mice was similar to that in saline-treated mice at 7 days after CFA injection. The present findings strongly indicate the early intrathecal use of the COX-2 inhibitor for the relief of chronic inflammatory pain. Furthermore, together with the result in a previous study that pro-inflammatory cytokines lead to stimulation of a NF-kappaB-dependent transcriptional pathway, these findings suggest that a spinal cytokine/NF-kappaB/COX-2 pathway may play an important role in the development, but not maintenance, of chronic pain following peripheral tissue inflammation.

Novel bioluminescent assay of alkaline phosphatase using adenosine-3'-phosphate-5'-phosphosulfate as substrate and the luciferin-luciferase reaction and its application

This paper describes a novel bioluminescent assay of alkaline phosphatase (ALP) utilizing ATP-sulfurylase and the luciferin-luciferase reaction. The principle governing the assay is as follows. Adenosine-3'-phosphate-5'-phosphosulfate, which serves as the substrate for ALP, is hydrolyzed enzymatically to produce adenosine-5'-phosphosulfate (APS). APS is converted into ATP by ATP-sulfurylase in the presence of pyrophosphate. The ATP produced is detected by the luciferin-luciferase reaction. The measurable range was 1 zmol to 100 fmol/assay and the detection limit at blank+3 SD was 10 zmol/assay. The coefficient of variation (CV, n=5) was examined at each point of the standard curve; the mean CV percentage was 4.47% (n=6). This assay system was applied to enzyme immunoassay of human chorionic gonadotropin and allele-specific PCR enzyme-linked immunosorbent assay of verotoxin gene using ALP as the label enzyme; 10(-2) mIU/mL hCG in urine and 5 pg of Escherichia coli O157 DNA could be assayed directly and with high sensitivity by the proposed method.

Identification of receptor-binding sites of monocyte chemotactic S19 ribosomal protein dimer

The S19 ribosomal protein (RP S19) cross-linked homo-dimer attracts monocyte migration by binding to C5a receptor on monocytes (H Nishiura, Y Shibuya, T Yamamoto, Laboratory Investigation, 1998, 78:1615-1623). Using site-directed mutants of recombinant RP S19 and synthetic peptides mimicking RP S19 molecular regions, we currently identified the binding sites of the RP S19 dimer to the C5a receptor. The RP S19 dimer activated the receptor by a two-step binding mechanism as in the case of C5a. The first binding site was a basic cluster region containing a -Lys41-His42-Lys43- sequence. The second one was the -Leu131-Asp132-Arg133- moiety, localized 12 residues upstream from the COOH-terminal. The second binding triggered the chemotactic response. The first binding would have a role in achieving a high-binding affinity between the ligand and receptor. The first and second ligand-binding sites of C5a receptor seem to be shared by C5a and the RP S19 dimer, although overall homology between the amino acid sequences of these ligands is only 4%.

Characteristics of body heat balance of paraplegics during exercise in a hot environment

The purpose of this investigation was to clarify the characteristics of body temperature regulation in paraplegics due to spinal cord injury (SCI) during an arm cranking exercise in a hot environment. Twelve paraplegics with lesions located between Th3 and L1,2 and seven able-bodied subjects (AB) participated in this study. The subjects were exposed to a hot (33 degrees C) or a moderate temperature (25 degrees C) environment for one hour and during the last 10 min of the exposure, the subjects performed arm cranking exercises at an exercise intensity of 40 W. The skin temperatures at the chest, the upper arm, the thigh and the calf, the tympanic membrane temperature (Tty), and the skin blood flow of the thigh (SBFT) were continuously monitored during the experiment. Although no systematical variation was found in the Tty at 25 degrees C, the Tty at 33 degrees C in paraplegics during exercise was significantly greater than that at rest (P < 0.01), which indicated a pronounced heat stress for paraplegics at 33 degrees C. SBFT of paraplegics with high lesions of the SCI remained unchanged during the experiment at 25 degrees C and 33 degrees C, while paraplegics with low lesions in this study showed consecutive increases in SBFT during exercise in both environmental conditions similar to AB. The increased core temperature in paraplegics with high lesions was considered to be due to a lack of sweat response and vasomotor activity in the paralyzed area. On the basis of the findings in this study, it can be suggested that high core temperature without any increment of SBFT may be characterized as body heat balance of paraplegics with high lesions during exercise in a hot environment.

Effect of wearing clothes on oxygen uptake and ratings of perceived exertion while swimming

For a comparative study between swimming in swimwear (control-sw) and swimming in clothes (clothes-sw), oxygen uptake (VO2) and ratings of perceived exertion (RPE) were measured. The subjects were six male members of a university swimming team. Three swimming strokes--the breaststroke, the front crawl stroke and the elementary backstroke--were applied. With regards to clothes-sw, swimmers wore T-shirts, sportswear (shirt and pants) over swimwear and running shoes. In both cases of control-sw and clothes-sw, the VO2 was increased exponentially with increased swimming speed. The VO2 of the subjects during the clothed tests did not exceed 1.4 times of that in the case of control-sw at swimming speeds below 0.3 m/s. As swimming speeds increased, VO2 difference in both cases increased. Consequently, VO2 in the clothed tests was equal to 1.5-1.6 times and 1.5-1.8 times of that in the swimwear tests at speeds of 0.5 and 0.7 m/s, respectively. At speeds below 0.6 m/s in clothes-sw, the breaststroke showed lower VO2 than the front crawl stroke, and the elementary backstroke showed higher VO2 than the other two swimming strokes. RPE increased linearly with %peak VO2. In addition, any RPE differences among the three swimming strokes were not shown in the control-sw tests. At an exercise intensity above 60 %peak VO2, clothed swimmers showed slightly higher RPE in the front crawl stroke compared to that in the two other swimming strokes.

Effect of acute heat exposure on skin blood flow of the paralyzed thigh in persons with spinal cord injury

OBJECTIVES

To investigate whether increased body temperature during heat exposure promotes skin blood flow of the thigh (SBFT) in individuals with spinal cord injury at rest.

STUDY DESIGN

A prospective study with high lesion and with low lesion.

SETTING

Hiroshima University, Higashi-Hiroshima, Japan.

METHODS

Seven male paraplegics (T5-L2) and seven able-bodied subjects volunteered to participate in the experiment. First the subject rested for 1 h at an ambient temperature (Ta) of 25 degrees C and a relative humidity (Rh) of 50%. Thereafter, the subject moved to a climatic chamber heated to Ta of 33 degrees C an Rh of 50 - 55% and was exposed to this environment for 1 h. SBFT, stroke volume, heart rate, the skin temperature of the medial thigh (Tthigh) and the tympanic membrane temperature (Tty) were assessed during the experiment.

RESULTS

The four subjects with high lesions between Th6 and Th10 (HL) showed no increase in SBFT, while the remaining three subjects with low lesion at Th11 or Th12 (LL) showed increased SBFT in the hot environment. Although Tty increased with exposure time in heat, correlation between Tty and SBFT was not significant in either paraplegic group. However, correlation between SBFT and Tthigh was highly significant in both groups. The increase in Tthigh in LL was due to increased skin blood flow in the thigh, while in HL it was considered attributable to heat transfer from the environment to the skin.

CONCLUSION

These findings indicate that SBFT during heat exposure was largely dependent on the level of spinal cord injury. SBFT with low lesions increased during heat exposure when the sympathetic cutaneous vasomotor supply of the thigh was preserved.

Estrogen inhibits bone resorption by directly inducing apoptosis of the bone-resorbing osteoclasts

Estrogen deficiency causes bone loss, which can be prevented by estrogen replacement therapy. Using a recently developed technique for isolation of highly purified mammalian osteoclasts, we showed that 17 beta-estradiol (E2) was able to directly inhibit osteoclastic bone resorption. At concentrations effective for inhibiting bone resorption, E2 also directly induced osteoclast apoptosis in a dose- and time-dependent manner. ICI164,384 and tamoxifen, as pure and partial antagonists, respectively, completely or partially blocked the effect of E2 on both inhibition of osteoclastic bone resorption and induction of osteoclast apoptosis. These data suggest that the protective effects of estrogen against postmenopausal osteoporosis are mediated in part by the direct induction of apoptosis of the bone-resorbing osteoclasts by an estrogen receptor- mediated mechanism.

Concanavalin A directly stimulates bone-resorbing activity of osteoclasts and their gene expression of cathepsin K/OC-2

Concanavalin A (Con A), a plant lectin that recognizes cell-surface glycoproteins, up-regulates osteoclastic bone-resorbing activity of cultured isolated rabbit pure osteoclasts as well as unfractionated bone cells. The effect of Con A was blocked by alpha-methyl mannopyranoside. Several Con A-binding proteins were detected in the plasma membranes from osteoclasts. Furthermore, Con A increased the levels of transcripts of cathepsin K/OC-2, one of the proteases responsible for osteoclastic bone-resorbing activity. These results indicate that Con A directly enhances the function of osteoclasts by the association with surface glycoproteins of osteoclasts.

Prostaglandin F2alpha stimulates tyrosine phosphorylation and mitogen-activated protein kinase in osteoblastic MC3T3-E1 cells via protein kinase C activation

PGF2alpha stimulates the proliferation of clonal osteoblastic MC3T3-E1 cells via PGF2alpha receptor linked to phospholipase C activation. To elucidate intracellular events elicited by this receptor, we examined the effects of PGF2alpha on tyrosine phosphorylation and mitogen-activated protein kinase (MAPK) activity in MC3T3-E1 cells. PGF2alpha rapidly raised the level of phosphotyrosine of cellular proteins with Mr values of 62, 68, 72, 76, 82, 125, and 150 kDa. This PGF2alpha-induced tyrosine phosphorylation of proteins (except for pp62) was blocked by down-regulating protein kinase C (PKC) by 12-O-tetradecanoylphorbol 13-acetate pretreatment and by GF 109203X, a potent specific PKC inhibitor. The addition of PGF2alpha also transiently activated MAPK in the same range of concentrations that stimulated tyrosine phosphorylation. In addition, PGF2alpha augmented the MAPK kinase kinase activity of Raf-1, whereas basal activity of MAPK/extracellular signal-regulated protein kinase kinase was less than that of Raf-1 and was little affected by PGF2alpha. Like the tyrosine phosphorylation, these activations of Raf-1 and MAPK activities were reduced by inhibition and down-regulation of PKC. Genistein, a potent inhibitor of tyrosine kinases, did not block the Raf-1 induced by PGF2alpha, indicating a tyrosine kinase-independent pathway for Raf-1 activation. However, the tyrosine kinase inhibitor partially inhibited the MAPK activity, suggesting an involvement of another Raf-1-independent kinase cascade for activation of MAPK by PGF2alpha. Fluprostenol, a specific agonist of PGF2alpha receptor, mimicked the actions of PGF2alpha consistent with a PGF2alpha receptor pathway. Thus, the action of PGF2alpha on osteoblastic MC3T3-E1 cells appears to involve a single receptor that uses diverse interacting signal transduction systems.

Stimulation of osteoblast proliferation by the cartilage-derived growth promoting factors chondromodulin-I and -II

We previously reported the isolation of the cartilage-derived growth promoting factors chondromodulin-I (ChM-I) and chondromodulin-II (ChM-II) from fetal bovine epiphyseal cartilage. Both of these factors stimulate the growth and matrix formation of chondrocytes in vitro. In the present study, we found that ChM-I and ChM-II stimulated the proliferation of clonal mouse osteoblastic MC3T3-E1 cells as well as primary mouse osteoblasts in culture. Unlike other known growth factors, these factors did not support the proliferation of fibroblasts. Concomitantly with growth stimulation of osteoblasts, there was a reduction of alkaline phosphatase (ALP) activity in the cells, the expression of the differentiated phenotype. These results suggest that epiphyseal cartilage may play a functional role in longitudinal bone growth by production of these unique growth-promoting factors.

Mammalian mature osteoclasts as estrogen target cells

The decrease in estrogen levels that follows the onset of menopause causes rapid bone loss, resulting in osteoporosis. However, the mechanism by which this occurs remains unclear, especially concerning the regulation of osteoclasts, i.e. the bone-resorbing cells. Using a pit assay involving isolated mature osteoclasts from rabbit long bones, we found that estrogen inhibited the bone-resorbing activity in a dose- and time-dependent manner. Furthermore, we clarified by Northern analysis that estrogen down-regulated the mRNA levels of cathepsin K/OC-2 and that putative estrogen receptor (ER) mRNA was expressed in these osteoclasts. Moreover, other sizes of mRNAs that hybridized with ER cDNA probe were found in these cells. Our results suggest that osteoclasts may be indeed target cells for estrogen and that estrogen might regulate a part of bone metabolism through osteoclasts.

Vitamin K2 inhibits osteoclastic bone resorption by inducing osteoclast apoptosis

In contrast to vitamin K1(VK1), vitamin K2(VK2) inhibited osteoclastic bone resorption by unfractionated bone cells and isolated osteoclasts. To investigate the mechanism of inhibition of osteoclastic bone resorption by VK2, we examined the effect of this vitamin on osteoclast apoptosis using a DNA-binding fluorescent dye, Hoechst 33258. In unfractionated bone cells and isolated osteoclasts on dentin slices, we first demonstrated that VK2 induced osteoclast apoptosis, but VK1 did not. Moreover, cycloheximide inhibited VK2-induced osteoclast apoptosis. These results suggest the possibility that VK2 inhibits osteoclastic bone resorption by targeting osteoclasts to undergo apoptosis, which leads to cell death.

[A comparative study between urinary metabolites of sustained-release theophylline and theophylline clearance in clinical use]

The relationships between changes in urinary metabolites and theophylline clearance were studied in 40 asthmatic children for each steady state phase. Urinary excretion of 1MU, DMU, 3MX increased with age. There were direct correlations between urinary metabolites, while urinary unchanged theophylline decreased and there was an inverse correlation between urinary metabolites. There was a significant correlation between the excretion of unchanged theophylline and 3MX (r = 0.597, p < 0.0001). The values of renal clearance and hepatic clearance also decreased with age. The changes in hepatic clearance were greater than those of renal clearance and showed a low correlation with unchanged theophylline (r = 0.247, p < 0.002), while the changes in renal clearance were high correlation with those of unchanged theophylline in urine. These changes were significant (r = 0.833, p < 0.0001). The changes in theophylline metabolites and its clearance are clinically important because the effective therapeutic range is narrow. Therefore, we concluded that it would be useful to determine the appropriate administration schedule of theophylline considering changes in renal clearance and urinary unchanged theophylline in different age groups.