Antisense oligonucleotides to p53 tumor suppressor suppress the induction of apoptosis by epidermal growth factor in NCI-H 596 human lung cancer cells

Apoptosis has become a basic tool in developing cancer research and establishing new cancer strategies. However, the molecular mechanism of apoptosis is not well understood. Recently, the authors found that epidermal growth factor (EGF) induces apoptosis in various cancer cells and that there is a novel signal pathway mediated through p53 in signal transduction of EGF. The effect of antisense gene therapy to p53 tumor suppressor on EGF-dependent apoptosis was investigated in cultured NCI-H 596 human non-small cell lung cancer cells with a wild-type p53 gene. Results showed that EGF plus p53 sense oligonucleotides induced EGF-dependent and p53-dependent apoptosis in NCI-H 596 cells within 8 hours. On the other hand, antisense gene therapy using antisense oligonucleotides to p53 tumor suppressor suppressed the induction of EGF-dependent and p53-dependent apoptosis. Mutated p53 antisense-containing mutated CG dinucleotides had the same effect as that of p53 antisense on suppression of apoptosis in NCI-H 596 cells. We found that a new nucleic acid drug, another mutated p53 antisense-containing mutation at three bases immediately 5' and 3' from the CG dinucleotides, potentiated the induction of apoptosis and failed to suppress the induction of EGF-dependent apoptosis. These results suggest that gene therapy using antisense oligonucleotides to the p53 tumor suppressor is effective on EGF-dependent apoptosis of NCI-H 596 human non-small cell lung cancer.

The receptor for advanced glycation end products mediates the chemotaxis of rabbit smooth muscle cells

Long-term incubation of proteins with glucose leads to advanced glycation end products (AGEs) with fluorescence and a brown color. We recently demonstrated immunologically the intracellular AGE accumulation in smooth muscle cell (SMC)-derived foam cells in advanced atherosclerotic lesions. To understand the mechanism of AGE accumulation in these foam cells, we have now characterized the interaction of AGE proteins with rabbit-cultured arterial SMCs. In experiments at 4 degrees C, 125I-labeled AGE-bovine serum albumin (AGE-BSA) showed a dose-dependent saturable binding to SMCs with an apparent dissociation constant (Kd) of 4.0 microg/ml. In experiments at 37 degrees C, AGE-BSA underwent receptor-mediated endocytosis and subsequent lysosomal degradation. The endocytic uptake of 125I-AGE-BSA was effectively inhibited by unlabeled AGE proteins such as AGE-BSA and AGE-hemoglobin, but not by acetylated LDL and oxidized LDL, well-known ligands for the macrophage scavenger receptor (MSR). Moreover, the binding of 125I-AGE-BSA to SMCs was affected neither by amphoterin, a ligand for one type of the AGE receptor, named RAGE, nor by 2-(2-furoyl)-4(5)-(2-furanyl)-1H-imidazole-hexanoic acid-BSA, a ligand for the other AGE receptors, p60 and p90. This indicates that the endocytic uptake of AGE proteins by SMCs is mediated by an AGE receptor distinct from MSR, RAGE, p60, and p90. To examine the functional role of this AGE receptor, the migratory effects of AGE-BSA on these SMCs were tested. Incubation with 1-50 microg/ml of AGE-BSA for 14 h resulted in significant dose-dependent cell migration. The AGE-BSA-induced SMC migration was chemotactic in nature and was significantly inhibited (approximately 80%) by an antibody against transforming growth factor-beta (TGF-beta), and the amount of TGF-beta secreted into the culture medium from SMC by AGE-BSA was sevenfold higher than that of control, indicating that TGF-beta is involved in the AGE-induced SMC chemotaxis. These data suggest that AGE may play a role in SMC migration in advanced atherosclerotic lesions.

Advanced glycation end products are eliminated by scavenger-receptor-mediated endocytosis in hepatic sinusoidal Kupffer and endothelial cells

Long-term incubation of proteins with glucose leads to the formation of advanced glycation end products (AGE). Physiological aspects of the catabolism of non-enzymically glycated proteins were studied in vivo and in vitro. AGE-modified BSA (AGE-BSA) was a mixture of high-Mr (cross-linked), monomeric and low-Mr (fragmented) AGE-BSA. After intravenous administration in rat, all three fractions of AGE-BSA accumulated extremely rapidly and almost exclusively in liver. Uptake in liver endothelial, Kupffer and parenchymal cells accounted for approx. 60%, 25% and 10-15% respectively of hepatic elimination. Both cross-linked and monomeric AGE-BSA were efficiently taken up and degraded in cultures of purified liver endothelial and Kupffer cells. Endocytosis of AGE-BSA by these cells was inhibited by several ligands for the scavenger receptor. Although 125I-Hb was not endocytosed in vitro, 125I-AGE-Hb was effectively endocytosed by a mechanism that was subject to inhibition by AGE-BSA. Endocytosis of N-terminal propeptide of type I procollagen, a physiological ligand for the scavenger receptor, was effectively inhibited by AGE-Hb and AGE-BSA. We conclude that AGE-modification renders macromolecules susceptible for elimination via the scavenger receptor of both liver endothelial and Kupffer cells.

Age patterns of the life table aging rate for major causes of death in Japan, 1951-1990

It has been widely supposed that human mortality from all causes increases with age nearly exponentially (at a constant rate) through adult ages except for very old ages, and that this exponential increase also holds fairly well for most major causes of death (CODs). However, the present analysis of death registration data for Japan, 1951-1990, reveals that the rate of age-related relative increase in mortality (the life table aging rate) changes with age significantly and systematically for many CODs. Above age 75, the mortality increase decelerates for most CODs; under age 75, it remains at a relatively stable pace for ischemic heart disease, decelerates for most major cancers, and accelerates for diseases related to a declining ability to maintain homeostasis (pneumonia, bronchitis, influenza, gastroenteritis, and heart failure). These results seem to suggest that significantly different types of senescent processes may underlie atherogenesis, oncogenesis, and immunosenescence.

Immunohistochemical detection of advanced glycosylation end-products in the peritoneum and its possible pathophysiological role in CAPD

It has recently been suggested that advanced glycosylation end-products (AGEs) are formed in the peritoneum in patients on CAPD. However, the exact location of AGE accumulation, the relation with the duration of CAPD and its pathophysiological role in CAPD remain unclear. If the peritoneum is glycosylated, it could bring about altered peritoneal function. Therefore, the aim of this study is to clarify the localization of AGEs in the peritoneum in accordance with the duration of CAPD and to examine its relation to the peritoneal permeability. Fifteen non-diabetic patients were divided into three groups (each 5 patients) on the basis of the mean duration (D) of CAPD (Group 1, D = 0 month; Group II, D = 34 months; Group III, D = 84 months). The AGE staining by monoclonal anti-AGE antibody in the peritoneum and the four-hour peritoneal equilibration test (PET) were compared among these groups. AGE was absent or found only weakly in Group I. However, in groups II and III, AGE was moderately or strongly positive especially in the vascular walls and it was dominant in group III. PET revealed that peritoneal permeability for glucose, creatinine, beta2-microglobulin and albumin was increased in Group II as compared to Group I, and it was further increased in Group III. The results of this study indicate that AGEs become dominantly accumulated in the vascular wall in accordance with the prolongation of CAPD treatment, and this might play some roles for the increased permeability of the peritoneal membrane in CAPD.

[A study of nursing systems in transition in developed countries]

The present study was designed to investigate nursing systems in other countries in comparison with the current system in Japan, and thereby assess how nursing personnel should be in order to improve the quality of nursing. The study focused on the actual situation of the nursing system and licensed practical nurses (LPNs) or second-level nurses similar to LPNs in other countries. The survey was conducted in regard to six countries considered to be advanced in the development of nursing activities and likely to provide useful suggestions for the future direction of nursing in Japan: Australia, Canada, France, Sweden, the United Kingdom and the United States. Questionnaires were sent to the heads or staff of a total of 29 organizations, including WHO Collaborating Centers and professional organizations for nursing, in these countries. Nineteen organizations responded (response rate: 65.5%), and an effective response with completed questionnaire forms was obtained from 15 organizations. In addition, an interview survey was conducted on three nursing administration and education experts in the United States in order to acquire clear understanding of the actual state of nursing in health care practice. The results were as follows: 1. Six countries (Japan included) excluding France had LPNs. Educational preparation for LPNs has been discontinued in the United Kingdom. 2. The number of nurses per 1,000 population was lowest in Japan: the total number of registered nurses (RNs) and LPNs in Japan was less than the number of RNs in the United Kingdom. Only in Japan the proportions of LPNs and RNs were similar, while in other countries of number of LPNs was one-third to one-fourth of the number of RNs. 3. In the five other countries having LPNs, the nurse's competency or scope of practice was clearly defined for both LPNs and RNs. In contrast, no clear line was drawn between the two in Japan. 4. The length of education required for LPNs ranged from 11 to 14 years (including the period of compulsory education) and was shortest in Japan (11 years). The educational requirement for admission to LPN school in Japan was 9 years of compulsory education (graduation from junior high school), whereas in other countries it was at the level of senior high school graduation. 5. Four countries had conversion programs for LPNs to become RNs, and the conversion courses were positioned within the framework of higher education comparable to the university level. 6. In the United Kingdom, where the educational preparation for LPNs has been discontinued, nurses are included in a single higher level profession. At the same time there was found to be a need to train and educate auxiliary personnel in order to maintain multi-level care services. Because of the increasing tendency toward advanced medical technology and highly specialized medical care associated with the rapidly increasing care needs in the community, the current educational preparation for LPNs in Japan in unsatisfactory as a training and educational system for nursing manpower to cope with the current situation. The above findings suggest that the education system for LPNs be reviewed with a view to discontinuing it and consolidating nursing education in Japan.

Histological localization of advanced glycosylation end products in the progression of diabetic nephropathy

We studied the immunohistochemical localization of advanced glycosylation end products (AGEs) in the progression of diabetic nephropathy. Fourteen NIDDM patients with diabetic nephropathy were evaluated: 2 patients with normoalbuminuria, 4 with microalbuminuria (MA) and 8 with overt proteinuria (OP). Three patients with minor glomerular abnormalities were used as nondiabetic controls. Immunoreactivity to a monoclonal anti-AGE antibody (6D12) was recognized on the internal elastic membranes of arterial walls in every diabetic group. Hyaline lesions of arterioles of the MA and OP groups demonstrated strong reactions with 6D12. A portion of the nodular and exudative lesions in glomeruli of OP group patients also revealed immunoreactivity to 6D12. No immunoreactivity to 6D12 was observed in nondiabetic control specimens. We confirm that the accumulation of AGEs began in arterial walls of the early stage and presented in glomerular lesions of the late stage of the progression of diabetic nephropathy.

Postmenopausal acceleration of age-related mortality increase

The force of natural selection to eliminate deleterious genes is attenuated with advancing age, allowing senescence to evolve. This suggests that a distinctly marked end of the reproduction period is likely to be followed by an acceleration of senescence. It is thus expected that menopause should trigger an acceleration of age-related mortality increase in human females. Such an abrupt initiation of mortality acceleration is not predicted for human males at the same ages, whose fecundity declines more gradually. Life table aging rate patterns for selected industrialized countries generally support this hypothesis. A cause-of-death decomposition analysis indicates that the sex differential in mortality acceleration is mainly due to cardiovascular diseases, which is consistent with the prevalent view that postmenopausal changes in the sex hormone status may affect lipoprotein metabolism, and in turn, raise the risk of arteriosclerosis.

Identification of advanced glycation end products of the Maillard reaction in Pick's disease

The recent identification of advanced glycation end products (AGEs) of the Maillard reaction in the central nervous system suggests their potential involvement in the aging process. Other studies have also suggested a possible link between AGEs and Alzheimer's disease. To investigate the role of AGEs in Pick's disease, another neurodegenerative disease associated with dementia, we examined the AGE-immunoreaction in Pick's bodies and ballooned neurons, two characteristic neuropathological features of Pick's disease, using antibodies against identified AGE-structures, N epsilon-(carboxymethyl)lysine and pentosidine. These two structures were observed immunohistochemically in Pick's bodies and ballooned neurons of brain tissues obtained at autopsy from three elderly patients diagnosed with Pick's disease. These immunoreactions were further confirmed by absorption experiments and double-immunostaining. The present findings suggest that AGEs are involved in the pathology of Pick's disease.

Rapid formation of advanced glycation end products by intermediate metabolites of glycolytic pathway and polyol pathway

To clarify roles of intermediate metabolites of the glycolytic pathway and the polyol pathway in nonenzymatic glycation under physiological conditions, we incubated bovine serum albumin with intermediates of both pathways in the micromolar range as well as with 20 mmol/l glucose, and observed the formation of advanced glycation end products (AGEs). We found that triose phosphates, glyceraldehyde, and a novel polyol pathway-related metabolite, fructose 3-phosphate along with its breakdown product, 3-deoxyglucosone were extremely potent glycating agents that at nearly physiological concentrations on incubation with albumin produced substantial amounts of AGEs as early as 24 hours, while 20 mmol/l glucose afforded trace amounts of AGEs after two week incubation. The results along with the previous evidence of the increased level of intermediates in diabetic states may suggest that the intermediate metabolites rather than glucose contribute to enhanced glycation in diabetic tissues, inspite of the much lower concentrations compared with glucose.

The scavenger receptor serves as a route for internalization of lysophosphatidylcholine in oxidized low density lipoprotein-induced macrophage proliferation

We have recently demonstrated that the growth of murine macrophages is induced by oxidized low density lipoprotein (Ox-LDL) and that lysophosphatidylcholine (lyso-PC), a major phospholipid component of Ox-LDL, plays an essential role in its mitogenic effect. The present study was undertaken to further characterize the role of the macrophage scavenger receptor (MSR) in Ox-LDL-induced macrophage growth. The growth-stimulating effect of Ox-LDL on murine resident peritoneal macrophages was inhibited by maleylated bovine serum albumin (maleyl-BSA), a non-lipoprotein ligand for MSR but a poor carrier of lyso-PC, while maleyl-BSA itself failed to induce macrophage growth even in the presence of lyso-PC. Moreover, it competitively inhibited the endocytic uptake of 125I-Ox-LDL and the specific uptake of lyso-PC by MSR, whereas nonspecific lyso-PC transfer to cells was not affected. Furthermore, the Ox-LDL-induced cell growth of peritoneal macrophages obtained from MSR knockout mice was significantly weaker than that of macrophages obtained from their wild-type littermates. Our results suggest that the MSR is an important and efficient internalization pathway for lyso-PC in Ox-LDL-induced macrophage growth.

Immunohistochemical study with anti-advanced glycation end-products antibody in murine amyloidosis

Advanced glycation end-products (AGE) are formed in the late phase of the non-enzymatic glycosylation reaction in conditions such as diabetes mellitus and aging. In amyloidosis, AGE have been found in the A beta 2M amyloid associated with long-term hemodialysis and in the beta-protein in Alzheimer's disease. Murine AApoAII and AA amyloidosis were examined immunohistochemically using anti-AGE monoclonal antibody, 6D12. AApoAII amyloid deposits studied in one senescence-accelerated mouse P1 (SAMP1), congenic mice that have the amyloidogenic apolipoprotein A-II of SAMP1 mice, and AKR mice all reacted with biotinylated 6D12 by formic acid pretreatment, whereas AA amyloid deposits did not react with the antibody. The immunoreaction with anti-apolipoprotein A-II for amyloid deposits in senile mice was approximately homogeneous in intensity; on the other hand the reaction with biotinylated 6D12 was irregular in distribution and intensity over the amyloid deposits. These findings suggest that amyloid precursor proteins are not associated uniformly with AGE modification before deposition as amyloid; it is more likely that the AGE modification progresses gradually and unevenly after amyloid deposition. Murine amyloidosis may be a useful model to elucidate the role of AGE in amyloidosis.

[An allogeneic bone marrow transplantation for chronic myelocytic leukemia with a large extramedullary tumor in the pelvic cavity]

A 16-year-old girl developed a pain and paresis in the right hip joint in April 1994. Abdominal CT scan revealed hepatosplenomegaly and large tumor mass (6 x 7 x 13 cm) invading the right psoas muscle in the pelvic cavity. Laboratory data disclosed marked granulocytosis, the presence of Ph1 translocation and bcr-abl rearrangement, thus a diagnosis of CML was made. The tumor was shown to be consisted of granulocytes at all stages of development by a fine needle aspiration cytology. According to the criteria of IBMTR, the disease was classified as accelerated phase solely because the sum of myeloblasts and promyelocytes exceeded over 20%. The patient was treated with hydroxycarbamide, 6MP and dexamethasone, and marked reduction of the tumor mass was observed. Then an allogeneic BMT was performed from her HLA- identical brother on August 1994. She did not develop clinically significant symptoms except for grade I skin GVHD. The tumor was completely disappeared after the BMT as assessed by the abdominal CT scan. No cytological and chromosomal relapse has been observed for 20 months after the BMT.

Quantitative analyses of lesion areas of coronary atherosclerosis in cholesterol-fed rabbits

A simple method to quantitatively evaluate atherosclerosis in the rabbit coronary arteries by measuring macroscopic lesion areas (%) was attempted in the present study. Sixteen rabbits were fed a 0.5% cholesterol diet for 15 weeks and then 9 rabbits were sacrificed whereas the remaining 7 rabbits were maintained for further 9 weeks on a normal chow (at week 24). The left circumflex coronary arteries (LCX) were excised from the rabbit hearts under stereoscopic observation. The prepared arterial strips of LCX were 38.7 +/- 7.1 mm long and all of them reached the cardiac apex from the orifice. At week 15, the lesion area in LCX was negligible (3.2 +/- 0.4%) whereas the aortic lesions significantly developed (50.0 +/- 7.6%). At week 24, atherosclerotic lesions in both LCX and aortas increased to 32.8 +/- 9.2% and 85.9 +/- 5.6%, respectively. This is the first report that determined the luminal surface areas of atherosclerotic lesions in rabbit coronary arteries. This method may be more practical and useful for quantitative evaluation of coronary atherosclerosis in a large number of rabbits than histological observations of serial sections of rabbit hearts.

Modification of vitronectin by advanced glycation alters functional properties in vitro and in the diabetic retina

Early diabetic retinopathy is characterized by areas of acellular capillaries and the accumulation of advanced glycation end products (AGE). Endothelial cell maintenance, growth, and migration is regulated by a complex system involving the partitioning of growth factors between extracellular matrix-bound proteoglycans and cells, as well as by the activation and control of pericellular proteolysis. Using specific antibodies, we compared the immunolocalization of the vascular heparan sulfate proteoglycan (HSPG)-binding protein vitronectin (VN), HSPG, basic fibroblast growth factor, and collagen type 1 in retinae prepared from 11-month-old diabetic and nondiabetic Wistar rats. In normal rats, VN immunostaining was prominent in vascularized parts of the inner retina and colocalized with HSPG, which itself showed costaining with basic fibroblast growth factor in the extracellular matrix, vascular walls, and the inner limiting membrane. In contrast, the recognition of VN, HSPG, and basic fibroblast growth factor in diabetic retinae was greatly reduced in the inner limiting membrane and the extracellular matrix, where increased immunoreactive AGE colocalizing with VN were detectable. Capillary labeling of retinal vessel walls for plasminogen activator inhibitor-1 was moderate in both normal and diabetic retinae. AGE-VN was demonstrated in tissue extracts from retina by immunoprecipitation and Western blotting and presented a similar increase of AGE-related immunoreactivity compared with AGE-VN generated in vitro. AGE-VN in vitro had lost its native conformation, yielded high Mr SDS-resistant products, and was resistant to proteolysis because of modification of about 30% of lysines. Because binding of glycosaminoglycans, as well as interaction of type I collagen and the morphoregulatory proteins osteonectin and tenascin with AGE-VN, were reduced to at least 50% of control, alteration of basic residues in the heparin-binding domain of VN is plausible. In comparison to nonmodified VN, AGE-VN exhibited reduced cell attachment-promoting activity. Together, these in vitro results suggest that AGE-VN found in vivo is related to morphologic and functional changes in the diabetic retina and may contribute to the genesis of acellular capillaries in early diabetic retinopathy.

Lipoprotein(a) induces cell growth in rat peritoneal macrophages through inhibition of transforming growth factor-beta activation

To elucidate the atherogenicity of lipoprotein(a) (Lp(a)), we examined its growth-stimulating activity in rat resident peritoneal macrophages. When macrophages were incubated with Lp(a), cell numbers were increased 1.5-fold as compared with control macrophages. Furthermore, apolipoprotein(a) (apo(a)), a plasminogen-like glycoprotein which is covalently attached to a low density lipoprotein-like particle (Lp(a)), also induced macrophage growth, while the growth-stimulating effect of Lp(a-) was negligible. These results suggest that apo(a) plays an active role in the mitogenic activity of Lp(a). Lp(a)-induced macrophage growth was inhibited by exogenously added active transforming growth factor-beta (TGF-beta) dose-dependently, and also by the addition of plasmin, which converts latent TGF-beta to an active form. Moreover, the amounts of endogenous active TGF-beta in the medium were significantly reduced by the incubation with Lp(a). It is evident from these results that Lp(a) induces macrophage growth by inhibiting TGF-beta activation. The capacity of Lp(a) to stimulate macrophage growth shown here could be novel atherogenic function of Lp(a).

Advanced glycation end products of the Maillard reaction in aortic pepsin-insoluble and pepsin-soluble collagen from diabetic rats

Recent immunohistological studies using antibodies against advanced glycation end products (AGEs) have demonstrated the presence of AGEs in several tissues. By an enzyme-linked immunosorbent assay using the monoclonal anti-AGE antibody, the present study aimed to determine AGEs in pepsin-insoluble collagen (PIC) as well as in pepsin-soluble collagen (PSC) from the aortas of streptozotocin (STZ)-induced diabetic rats (at 4, 16, and 28 weeks after STZ injection) and those of age-matched control rats. Addition of EDTA to the immunoassay buffer has led us to successful determination of AGEs in the aortic PIC samples with following results: 1) in diabetic rats, there was a time-related increase in the AGE contents at 28 weeks (n = 9, 226.4 +/- 13.5 ng/mg collagen [mean +/- SE]), compared with that at 4 and 16 weeks (n = 6, 79.6 +/- 9.5 ng/mg collagen, and n = 8, 149.4 +/- 30.9 ng/mg collagen at 4 and 16 weeks, respectively; both P < 0.05, between 4 and 16 weeks and 28 weeks); 2) after 28 weeks of diabetes, the AGE contents in PIC of aortas were significantly higher in diabetic rats than in controls (n = 9, 226.4 +/- 13.5 ng/mg collagen vs. n = 8, 129.6 +/- 14.9 ng/mg collagen, P < 0.01, diabetic vs. control); and 3) the level of the AGE content was strongly correlated with the PIC/total collagen (TC) ratio (n = 45, r = 0.698, P = 0.0001). By treating the samples of PSC with alkaline solution, the AGE content of PSC was also determined. In the PSC fraction, the AGE levels in the diabetic rats tended to increase with time and to be higher than those of control rats at 28 weeks although these changes were not statistically significant (diabetic: n = 4, 19.4 +/- 9.7; n = 6, 22.3 +/- 6.2; n = 6, 39.6 +/- 10.8; control: n = 4, 19.7 +/- 9.8; n = 6, 22.9 +/- 7.3; n = 7, 30.7 +/- 7.2; at 4, 16, and 28 weeks, respectively). Compared with the AGE levels of PSC, those of PIC were about four to seven times and four to five times higher in diabetic and control rats, respectively (PIC versus PSC in diabetic or control rats, all P < 0.001, at 4, 16, and 28 weeks, respectively). These findings provide the first immunochemical evidence that AGE adducts are present in the materials extracted sequentially by pepsin and collagenase and that these adducts in PIC accumulated as a function of the increase in the aortic PIC/TC ratio.

Advanced glycation end products and their recognition by macrophage and macrophage-derived cells

Modification of proteins by long-term incubation with glucose leads to the formation of advanced glycation end products (AGEs). AGE proteins are taken up by macrophages via the AGE receptor, which is similar to the macrophage scavenger receptor (MSR). In the present study, we compared the ligand specificity of the AGE receptor with that of MSR by three different experiments. The endocytic uptake of 125I-acetyl-LDL by RAW cells was effectively inhibited by unlabeled AGE-bovine serum albumin (BSA), whereas the inhibitory effect of acetyl-LDL on 125I-AGE-BSA was partial. Polyanions showing an effective inhibition for endocytic uptake of AGE-BSA were not always inhibitory for endocytic degradation of acetyl-LDL. These data, together with those obtained by three-dimensional fluorescence-activated cell sorter analysis, indicate that AGE proteins are recognized by more than two receptors, of which MSR is at least one. Finally, we examined whether MSR could mediate the endocytic uptake of AGE proteins by Chinese hamster ovary cells overexpressing bovine type II MSR (CHO-SRII cells). 125I-AGE-BSA underwent endocytic degradation by CHO-SRII cells, and this was effectively inhibited by unlabeled acetyl-LDL. These results clearly show that MSR mediates the endocytic uptake of AGE proteins, suggesting a new role of MSR in biological recognition of AGE in vivo.

N (epsilon)-(carboxymethyl)lysine protein adduct is a major immunological epitope in proteins modified with advanced glycation end products of the Maillard reaction

Long-term incubation of proteins with glucose leads to the formation of advanced glycation end products (AGE). Recent immunological studies have suggested the potential role of AGE in atherosclerosis, aging, and diabetic complications. We previously prepared a monoclonal (6D12) as well as a polyclonal anti-AGE antibody and proposed the presence of a common AGE structure(s) that may act as a major immunochemical epitope [Horiuchi, S., Araki, N., & Morino, Y. (1991) J. Biol. Chem. 266, 7329-7332]. The purpose of the present study was to determine the major epitope. Amino acid analysis of AGE-proteins indicated that N(epsilon)-(carboxymethyl)lysine (CML) was a major modified lysine residue. Immunologic studies demonstrated the positive reaction of 6D12 not only to all CML-modified proteins tested, but also to BSA modified with several aldehydes known to generate a CML-protein adduct, and a linear correlation between the CML contents of CML-BSA and their immunoreactivity to 6D12 up to approximately 8 mol/mol of protein. Further experiments with CML analogs revealed that the epitope of 6D12 is a CML-protein adduct with an important carbonyl group. In contrast to 6D12, our polyclonal anti-AGE antibody showed a significant but much weaker immunoreactivity to CML-BSA, suggesting that the polyclonal antibody contains two populations, one reactive to CML (CML-PA) and the other unreactive to CML (Non-CML-PA). Non-CML-PA separated from CML-PA by CML-BSA affinity chromatography did not react with all CML-modified preparations, but retained its property to react commonly with AGE preparations obtained from proteins, lysine derivatives, and monoaminocarboxylic acids. Therefore, it is clear that a CML-protein adduct is a major immunological epitope in AGE structures, but there still exist other major epitope(s) expressed commonly in AGE-proteins.

Vitamin B6 deficiency accelerates metabolic turnover of cystathionase in rat liver

Although most of cystathionase was found to exist as an inactive apoenzyme in the liver of vitamin B6-deficient rats, the concentrations of the immunoreactive enzyme protein were virtually the same for control and vitamin B6-deficient livers. Under vitamin B6 deficiency, however, the rate of synthesis of cystathionase, measured by incorporation of labeled amino acid into the immunoprecipitated enzyme, was increased severalfold due to an increased level of cystathionase mRNA. Western blot analysis of lysosomal proteins showed that the amount of cystathionase in the lysosomes from the liver of vitamin B6-deficient rats was also increased severalfold. This observation suggests that lysosomes specifically recognize the apocystathionase for sequestration in preference to the holoenzyme. The present study provides the molecular basis for dual roles of vitamin B6 in controlling the metabolic turnover of cystathionase; it regulates synthesis of the enzyme by modulating the expression of cystathionase gene, and it regulates degradation of the enzyme by different susceptibilities of apo- and holoenzymes to lysosomal proteolysis.