Deficiency of kallikrein-like enzyme activities in cerebral tissue of patients with alzheimer's disease

Summary We examined the changes in the intracerebral activities, at the time of postmortem autopsy, in patients with Alzheimer's disease. When compared with the control group, the activity of kallikrein-like enzyme was significantly decreased, while prolyl endopeptidase activity increased, in the patients group. Aprotinin inhibited 50% of the activity of the former enzyme at 2×10^–7M. Taken together with the results of a multivariate study, the above findings may indicate that intracerebral kallikrein deficiency plays an important role in the pathogenesis of Alzheimer's disease.     

Overexpression of copper-zinc superoxide dismutase in trisomy 21

Down's syndrome (DS), the most frequent of congenital birth defects, results from the trisomy of chromosome 21 in all cells of affected patients. This disease is characterized by developmental anomalies, mental retardation and features of rapid aging, particularly in the brain, where the occurrence of Alzheimer's disease is observed in trisomy 21 patients over the age of 35. Copper-zinc superoxide dismutase (CuZnSOD) is one of the proteins encoded by chromosome 21 (21q22.1). As a consequence of gene dosage excess, CuZnSOD activity is increased by 50% in all DS tissues. This work reports the SOD activity of a population of DS patients with complete trisomy 21, partial trisomy 21, translocations and mosaicism, in order to confirm the gene dosage effect of SOD on the clinical features of DS, and to help to establish which is the critical region of chromosome 21 in DS. CuZnSOD was measured in red blood cells using the Minami and Yoshikawa method. In the population with complete trisomy 21, SOD activity was increased by 42%; in the population with partial trisomy 21, translocations and mosaicism, SOD activity was normal. In the population diagnosed as DS, but not karyotyped, SOD activity was increased by 28%. No differences between sexes or among ages were found. We conclude that the 21q22.1 segment is not the critical region responsible for DS, as we have found normal SOD activity in patients with the clinical features of DS.     

Galanin – 25 years with a multitalented neuropeptide

The neuropeptide galanin and its receptors are localized in brain pathways mediating learning and memory. Central microinjection of galanin impairs performance of a variety of cognitive tasks in rats. Transgenic mice overexpressing galanin display deficits in some learning and memory tests. The inhibitory role of galanin in cognitive processes, taken together with the overexpression of galanin in Alzheimer's disease, suggests that galanin antagonists may offer a novel therapeutic approach to treat memory loss in Alzheimer's patients.     

Metabolic implications in the elevation of serum activity of intestinal alkaline phosphatase in chronic renal failure

The activity of intestinal isoenzyme of serum alkaline phosphatase was evaluated in 21 non-dialyzed patients with advanced renal failure and in 52 patients on regular hemodialysis. In patients without hepatopathy, a significant inverse correlation was found between the enzyme activity and serum calcium levels. Hepatopathy was the most significant variable influencing the enzyme activity in patients on dialysis. Secondary hyperparathyroidism and a decreased rate in enzyme elimination should be assessed for the above-normal activities of intestinal ALP in serum in chronic renal failure.     

Metabolic implications in the elevation of serum activity of intestinal alkaline phosphatase in chronic renal failure

Summary The activity of intestinal isoenzyme of serum alkaline phosphatase was evaluated in 21 non-dialyzed patients with advanced renal failure and in 52 patients on regular hemodialysis. In patients without hepatopathy, a significant inverse correlation was found between the enzyme activity and serum calcium levels. Hepatopathy was the most significant variable influencing the enzyme activity in patients on dialysis. Secondary hyperparathyroidism and a decreased rate in enzyme elimination should be assessed for the above-normal activities of intestinal ALP in serum in chronic renal failure.     

Metabolic implications in the elevation of serum activity of intestinal alkaline phosphatase in chronic renal failure

Summary The activity of intestinal isoenzyme of serum alkaline phosphatase was evaluated in 21 non-dialyzed patients with advanced renal failure and in 52 patients on regular hemodialysis. In patients without hepatopathy, a significant inverse correlation was found between the enzyme activity and serum calcium levels. Hepatopathy was the most significant variable influencing the enzyme activity in patients on dialysis. Secondary hyperparathyroidism and a decreased rate in enzyme elimination should be assessed for the above-normal activities of intestinal ALP in serum in chronic renal failure.     

Metabolic implications in the elevation of serum activity of intestinal alkaline phosphatase in chronic renal failure

The activity of intestinal isoenzyme of serum alkaline phosphatase was evaluated in 21 non-dialyzed patients with advanced renal failure and in 52 patients on regular hemodialysis. In patients without hepatopathy, a significant inverse correlation was found between the enzyme activity and serum calcium levels. Hepatopathy was the most significant variable influencing the enzyme activity in patients on dialysis. Secondary hyperparathyroidism and a decreased rate in enzyme elimination should be assessed for the above-normal activities of intestinal ALP in serum in chronic renal failure.     

Urinary excretion of renal brush border membrane enzymes in leprosy patientseffect of multidrug therapy

Renal function at the brush border membrane level has been studied using characteristic enzymes, such as alkaline phosphatase, leucine-aminopeptidase and gamma-glutamyl transpeptidase. Urinary enzyme studies were performed using leprosy patients, classified on the basis of bacteriological index (BI>3; n=20,BI<3; n=12, BI-ve; n=10) and compared with control subjects (n=10). The role of enzymuria in monitoring WHO-recommended multidrug therapy (MDT) has been evaluated in these patients. A significant increase in the enzyme activities (p<0.01), as well as significant (p<0.01) proteinurea in 24-hour urine samples of both the smear positive groups (BI>3,BI<3) prior to therapy compared to control subjects, indicates proximal tubular functional impairment at brush border membrane level. In the smear negative (BI-ve) grou, no significant difference was observed in enzyme activities as compared with the control group. In a follow-up study (BI>3; n=13, BI<3; n=4) the activities of all the enzymes decreased significantly in all the groups when compared to a corresponding untreated group. The follow-up study was not carried out on the smear negative group. The surprising finding was the differential behaviour of r-glutamyl transpeptidase, whose activity increased significantly (p<0.01) even after therapy inBI>3 group when compared with untreated patients. However in a detailed work-up including hepatic and renal function tests, the serum biochemistry was found to be normal both before and after therapy. Urinary excretion of brush border enzymes seems to be related to bacterial load, and their potential in studying the effect of MDT remains unclear.     

Targeting microglia-mediated neurotoxicity: the potential of NOX2 inhibitors

Microglia are key sentinels of central nervous system health, and their dysfunction has been widely implicated in the progressive nature of neurodegenerative diseases. While microglia can produce a host of factors that are toxic to neighboring neurons, NOX2 has been implicated as a common and essential mechanism of microglia-mediated neurotoxicity. Accumulating evidence indicates that activation of the NOX2 enzyme complex in microglia is neurotoxic, both through the production of extracellular reactive oxygen species that damage neighboring neurons as well as the initiation of redox signaling in microglia that amplifies the pro-inflammatory response. More specifically, evidence supports that NOX2 redox signaling enhances microglial sensitivity to pro-inflammatory stimuli, and amplifies the production of neurotoxic cytokines, to promote chronic and neurotoxic microglial activation. Here, we describe the evidence denoting the role of NOX2 in microglia-mediated neurotoxicity with an emphasis on Alzheimer's and Parkinson's disease, describe available inhibitors that have been tested, and detail evidence of the neuroprotective and therapeutic potential of targeting this enzyme complex to regulate microglia.     

Alzheimer's disease: fundamental and therapeutic aspects

Alzheimer's disease is the most common type of progressive and debilitating dementia affecting aged people. In some early — as well as late-onset familial cases, a genetic linkage with chromosomes 14, 21 (early-onset) or 19 (late-onset) has been indicated. Furthermore, a direct or indirect role has been attributed to normal or structurally altered amyloid -protein (concentrated in senile plaques) and/or excessively phosphorylated tau protein (located in neurofibrillary tangles). Degeneration of cholinergic neurons and concomitant impairment of cortical and hippocampal neurotransmission lead to cognitive and memory deficits. Several compounds are being tested in attempts to prevent and/or cure Alzheimer's disease, including tacrine, which has very modest efficacy in a sub-group of patients, and new acetylcholinesterase inhibitors. Pilot experiments have also been launched using nerve growth factor (NGF) to prevent or stabilize the processes of cholinergic pathway degeneration. Alternatively, antioxidants, free radical scavengers and/or non steroidal anti-inflammatory agents may be screened as potential therapies for neurodegenerative diseases induced by multiple endogenous and/or exogenous factors. The recent use of transgenic mice, in parallel with other genetic, biochemical and neurobiological systems, in vivo and/or in vitro (cell cultures), should accelerate the discovery and development of specific drugs for the treatment of Alzheimer's disease.     

Amyloid β-degrading cryptidases: insulin degrading enzyme, presequence peptidase, and neprilysin

The accumulation of aggregates of amyloidogenic peptides is associated with numerous human diseases. One well studied example is the association between deposition of amyloid beta (Abeta) and Alzheimer's disease. Insulin degrading enzyme and neprilysin are involved in the clearance of Abeta, and presequence peptidase is suggested to play a role in the degradation of mitochondrial Abeta. Recent structural analyses reveal that these three peptidases contain a catalytic chamber (crypt) that selectively encapsulates and cleaves amyloidogenic peptides, hence the name cryptidase. The substrate selectivity of these cryptidases is determined by the size and charge distribution of their crypt as well as the conformational flexibility of substrates. The interaction of Abeta with the catalytic core of these cryptidases is controlled by conformational changes that make the catalytic chambers accessible for Abeta binding. These new structural and biochemical insights into cryptidases provide potential therapeutic strategies for the control of Abeta clearance.     

What’s new in the renin-angiotensin system?

Angiotensin-converting enzyme 2 (ACE2) is a recently discovered homologue of the key enzyme of the renin-angiotensin system, the angiotensin-converting enzyme. The ACE2 enzyme is mainly expressed in cardiac blood vessels and tubular epithelia of the kidneys. Together with ACE2's unique metallocarboxypeptidase activity, the restricted tissue distribution suggests a distinctive physiological function in blood pressure, blood flow and fluid regulation. The ace2 gene was mapped to quantitative trait loci affecting susceptibility to hypertension in rats. Furthermore, ACE2 appears to be a negative regulator of ACE in the heart. ACE2 messenger RNA and protein levels are substantially regulated in the kidney of diabetic and pregnant rats. The mechanism of ACE2 function and its physiologic significance are not yet fully understood; however, as ACE2 differs in its specificity and physiological role from ACE, this opens a new potential venue for drug discovery aimed at cardiovascular disease, hypertension and diabetic complications.     

Monogenetic determinants of Alzheimer's disease: APP mutations

Mutations within exons 16 and 17 of the β-amyloid precursor protein (APP) gene were the first known cause of familial Alzheimer's disease. These mutations are rare and have been reported in a handful of families exhibiting autosomal dominant inheritance of Alzheimer's disease with age of onset around 50 years. In vitro and in vivo studies have demonstrated that each of these mutations alters proteolytic processing of APP, resulting in an increase in the production of Aβ42, a highly fibrillogenic peptide, that spontaneously aggregates and deposits in the brain. Transgenic mice carrying a mutant human APP gene also show age-dependent β-amyloid (Aβ) deposition in the brain. The rate of deposition in these mice can be modified by apolipoprotein E expression.     

In vivo effect of sodium valproate on mouse liver

The in vivo effect of sodium valproate (SV) on the activity of uridine diphosphate glucuronosyltransferase (UDP-GT) and hepatotoxicity in the mouse liver was studied. Mice were injected intraperitoneally (IP) with SV at doses varying from 50 to 800 mg/kg per day, for six consecutive days (dose-response group) or at a standard dose of 300 mg/g per day for 2-10 days (time-response group), whereas the controls were injected with normal saline. Valproic acid levels had a positive correlation to the dose (P < 0.001) and duration of drug administration (P = 0.006). A gradual increase in UDP-GT activity was observed in doses of up to approximately 400 mg/kg per day, whereas in higher doses the enzyme activity gradually decreased. The time course of UDP-GT activity at the standard dose of 300 mg/kg per day increased progressively, with a maximum up to the sixth day and then had a gradual reduction. Hepatic necrosis (which was unrelated to the dose or the duration of drug administration) was found in 13% of the SV-treated animals and in none of the controls. We conclude that at an optimal dose (300-400 mg/kg per day) and at a time course of 6 days, SV causes liver UDP-GT induction, whereas in higher doses and longer duration of administration, UDP-GT activity is gradually reduced. SV also causes hepatotoxicity unrelated to dose and time course.     

Reduction of serum X-prolyl dipeptidyl-aminopeptidase activity in tumour-bearing mice and reversal of reduced enzyme activity by lentinan,an anti-tumour polysaccharide

Summary Serum X-prolyl dipeptidyl-aminopeptidase activity which had been shown to be depressed in cancer patients was clearly reduced in mice with Ehrlich carcinoma and Sarcoma 180, and slightly reduced in mice with methylcholanthrene-induced sarcomas. The reduced enzyme activity was completely reversed during tumour regression of sarcoma 180 by administration of lentinan, which causes regression of sarcoma 180.     

Chitotriosidase: the yin and yang

The enzyme chitotriosidase (ChT), the human analogue of chitinases from non-vertebrate species, is one of the most abundant and indicative proteins secreted by activated macrophages. Its enzymatic activity is elevated in serum of patients suffering from Gaucher’s disease type 1 and in some other inherited lysosomal storage disorders, as well as in diseases in which macrophages are activated. The last decade has witnessed the appearance of a substantial number of studies attempting to unravel its cellular functions, which have yet not been fully defined. A great deal of progress has been made in the study of the physiological roles of ChT. This review is looks at the key areas of investigations addressed to further illuminate whether ChT activation might have different functional meanings in various diseases. Received 7 June 2006; received after revision 24 July 2006; accepted 21 September 2006     

Reduction of serum X-prolyl dipeptidyl-aminopeptidase activity in tumour-bearing mice and reversal of reduced enzyme activity by lentinan, an anti-tumour polysaccharide.

Serum X-prolyl dipeptidyl-aminopeptidase activity which had been shown to be depressed in cancer patients was clearly reduced in mice with Ehrlich carcinoma and Sarcoma 180, and slightly reduced in mice with methylcholanthrene-induced sarcomas. The reduced enzyme activity was completely reversed during tumour regression of sarcoma 180 by administration of lentinan, which causes regression of sarcoma 180.     

Decreased levels of complex III core protein 1 and complex V beta chain in brains from patients with Alzheimer's disease and Down syndrome

Ubiquinol:cytochrome c oxidoreductase (complex III) and ATP synthase (complex V) are important enzymes in the mitochondrial electron transport chain. Defects in mitochondrial respiratory enzymes have been reported for several neurodegenerative diseases. In this study, we applied the proteomic approach to investigate protein levels of complex III core protein and complex V beta chain in brain regions of Alzheimer's disease (AD) and Down syndrome (DS) patients. Complex III core protein 1 was significantly reduced in the temporal cortex of AD patients. Complex V beta chain was significantly reduced in the frontal cortex of DS patients. We conclude that decreased mitochondrial respiratory enzymes could contribute to the impairment of energy metabolism observed in DS. These decreases could also cause the generation of reactive oxygen species and neuronal cell death (apoptosis) in DS as well as AD.