A Student-Driven Community Engagement Model for School Nutrition Education Programs

BACKGROUND

Parental engagement in nutrition education programs often focuses on direct communication with parents. While this is an important component for the success of nutrition education, the role that students can play in connecting the program to their home is often overlooked.

METHODS

Feedback from students participating in a nutrition education program was used to develop an intervention that allowed students to take snacks they prepared in class home to their families. Change in parental awareness and family communication about the program was assessed in response to this intervention. A total of 257 third-grade students and 80 of their parents completed surveys to assess communication and interest in learning more about nutrition through the program.

RESULTS

A significant increase in family awareness and communication about the nutrition program was reported in response to the intervention that gave the students the ability to share food they made in class with their families.

CONCLUSIONS

Community engagement for school nutrition education programs is effective in stimulating family conversation about nutrition when methods are cognizant of students potential and motivation for driving these conversations. Our model for student-centered community engagement can be used by nutrition education programs to increase parental engagement.

Pancreatic alpha-cell mass across adult human lifespan

AIM

To establish pancreatic alpha-cell mass in lean, non-diabetic humans over the adult lifespan, performed as a follow-up study to beta-cell mass across the adult human lifespan.

METHODS

We examined human pancreatic autopsy tissue from 66 lean, non-diabetic individuals aged from 30 to 102 years, grouped into deciles: 3rd (30-39 years), 4th (40-49 years), 5th (50-59 years), 6th (60-69 years), 7th (70-79 years), 8th (80-89 years) and 9th deciles (90+ years). Sections of pancreas were immunostained for glucagon and analyzed for fractional alpha-cell area. Population-based pancreatic volume data were used to calculate alpha-cell mass.

RESULTS

With advanced age, the exocrine pancreas undergoes atrophy demonstrated by increased fat area (as % exocrine area) (0.05 ± 0.01 vs 1.6 ± 0.7% fat area of total exocrine pancreas, 3rd vs 9th decile, P < 0.05). Consequently, islet density increases with age (2.7 ± 0.4 vs 10.5 ± 3.3 islets/mm2, 3rd vs 9th decile, P < 0.05). Alpha-cell fractional area increases with advanced age (0.34 ± 0.05% vs 0.73 ± 0.26%, 3rd vs 9th decile, P < 0.05). However, alpha-cell mass remains constant at ~190 mg throughout the adult lifespan in lean, non-diabetic humans. Within islets, alpha-cell distribution between mantle and core is unchanged across deciles (1862 ± 220 vs 1945 ± 200 vs 1948 ± 139 alpha cells in islet mantle/mm2, 3rd vs 6th vs 9th decile, P = 0.93 and 1912 ± 442 vs 1449 ± 123 vs 1514 ± 168 alpha cells in islet core/mm2, 3rd vs 6th vs 9th decile, P = 0.47), suggesting that human islets retain their structural organization in the setting of age-related exocrine atrophy.

CONCLUSIONS

Consistent with our previous findings for beta-cell mass, alpha-cell mass remains constant in humans, even with advanced age. Pancreatic endocrine cells are much more robustly preserved than exocrine cells in aged humans, and islets maintain their structural integrity throughout life.

Characterization of Non-hormone Expressing Endocrine Cells in Fetal and Infant Human Pancreas

Context: Previously, we identified chromograninA positive hormone-negative (CPHN) cells in high frequency in human fetal and neonatal pancreas, likely representing nascent endocrine precursor cells. Here, we characterize the putative endocrine fate and replicative status of these newly formed cells. Objective: To establish the replicative frequency and transcriptional identity of CPHN cells, extending our observation on CPHN cell frequency to a larger cohort of fetal and infant pancreas. Design, Setting, and Participants: 8 fetal, 19 infant autopsy pancreata were evaluated for CPHN cell frequency; 12 fetal, 24 infant/child pancreata were evaluated for CPHN replication and identity. Results: CPHN cell frequency decreased 84% (islets) and 42% (clusters) from fetal to infant life. Unlike the beta-cells at this stage, CPHN cells were rarely observed to replicate (0.2 ± 0.1 vs. 4.7 ± 1.0%, CPHN vs. islet hormone positive cell replication, p < 0.001), indicated by the lack of Ki67 expression in CPHN cells whether located in the islets or in small clusters, and with no detectable difference between fetal and infant groups. While the majority of CPHN cells express (in overall compartments of pancreas) the pan-endocrine transcription factor NKX2.2 and beta-cell specific NKX6.1 in comparable frequency in fetal and infant/child cases (81.9 ± 6.3 vs. 82.8 ± 3.8% NKX6.1+-CPHN cells of total CPHN cells, fetal vs. infant/child, p = 0.9; 88.0 ± 4.7 vs. 82.1 ± 5.3% NKX2.2+-CPHN cells of total CPHN cells, fetal vs. infant/child, p = 0.4), the frequency of clustered CPHN cells expressing NKX6.1 or NKX2.2 is lower in infant/child vs. fetal cases (1.2 ± 0.3 vs. 16.7 ± 4.7 clustered NKX6.1+-CPHN cells/mm2, infant/child vs. fetal, p < 0.01; 2.7 ± 1.0 vs. 16.0 ± 4.0 clustered NKX2.2+-CPHN cells/mm2, infant/child vs. fetal, p < 0.01). Conclusions: The frequency of CPHN cells declines steeply from fetal to infant life, presumably as they differentiate to hormone-expressing cells. CPHN cells represent a non-replicative pool of endocrine precursor cells, a proportion of which are likely fated to become beta-cells. Precis : CPHN cell frequency declines steeply from fetal to infant life, as they mature to hormone expression. CPHN cells represent a non-replicative pool of endocrine precursor cells, a proportion of which are likely fated to become beta-cells.

An Increase in Chromogranin A-Positive, Hormone-Negative Endocrine Cells in Pancreas in Cystic Fibrosis

We sought to establish whether an increase in chromogranin A-positive, hormone-negative (CPHN) endocrine cells occurs in the pancreas of patients with cystic fibrosis (CF), as potential evidence of neogenesis. Pancreata were obtained at autopsy from nondiabetic patients with CF (n = 12) and age-matched nondiabetic control subject (CS) individuals without CF (n = 12). In addition, pancreas from three diabetic patients with CF was obtained. Pancreas sections were stained for chromogranin A, insulin, and a cocktail of glucagon, somatostatin, pancreatic polypeptide, and ghrelin and evaluated for the frequency of CPHN cells. There was a higher frequency of CPHN cells in islets of the patients with CF compared with the CS group. Moreover, CPHN cells occurring as single cells or clusters scattered in the exocrine pancreas were also more frequent in patients with CF. The increased frequency of CPHN cells in pancreas of patients with CF may indicate an attempt at endocrine cell regeneration.

Increased Chromogranin A-Positive Hormone-Negative Cells in Chronic Pancreatitis

CONTEXT

Chronic pancreatitis (CP) is characterized by inflammation, fibrosis, and a loss of pancreatic acinar cells, which can result in exocrine and eventually endocrine deficiency. Pancreatitis has been reported to induce formation of new endocrine cells (neogenesis) in mice. Our recent data have implicated chromogranin A-positive hormone-negative (CPHN) cells as potential evidence of neogenesis in humans.

OBJECTIVE

We sought to establish if CPHN cells were more abundant in CP in humans.

DESIGN, SETTING, AND PARTICIPANTS

We investigated the frequency and distribution of CPHN cells and the expression of the chemokine C-X-C motif ligand 10 (CXCL10) and its receptor chemokine C-X-C motif receptor 3 in pancreas of nondiabetic subjects with CP.

RESULTS

CPHN cell frequency in islets was increased sevenfold in CP [2.1% ± 0.67% vs 0.35% ± 0.09% CPHN cells in islets, CP vs nonpancreatitis (NP), P < 0.01], as were the CPHN cells found as scattered cells in the exocrine areas (17.4 ± 2.9 vs 4.2 ± 0.6, CP vs NP, P < 0.001). Polyhormonal endocrine cells were also increased in CP (2.7 ± 1.2 vs 0.1 ± 0.04, CP vs NP, % of polyhormonal cells of total endocrine cells, P < 0.01), as was expression of CXCL10 in α and β cells.

CONCLUSION

There is increased islet endogenous expression of the inflammation marker CXCL10 in islets in the setting of nondiabetic CP and an increase in polyhormonal (insulin-glucagon expressing) cells. The increase in CPHN cells in CP, often in a lobular distribution, may indicate foci of attempted endocrine cell regeneration.

Links between the organization of the family home environment and child obesity: a systematic review

Due to increasingly high rates of child overweight and obesity, it is important to identify risk and protective factors that may inform more effective prevention and intervention. The degree of organization in the family home environment is a studied, but not well-specified, factor that may impact child weight. Prior research on household organization has examined an array of constructs, including family routines, limit setting, household chaos, crowding and the broad home environment. This study systematically reviews literature on organization within the family home environment and weight among children ages 2-12. Six hundred thirty-seven studies were reviewed by four coders for eligibility, and 32 studies were included in the final synthesis. Overall, 84% of studies provided evidence for relations between at least one indicator of organization within the family home environment and child weight. Studies provided compelling evidence across several constructs, suggesting that the relevance of household organization to child weight extends beyond a single indicator. Directions for future work include (i) examining the mediating role of health behaviours, (ii) examining the moderating role of socioeconomic factors, (iii) broadening this evidence base across cultures and nationalities and (iv) integrating constructs to develop a comprehensive model of organization within the home environment.

Pancreatic Nonhormone Expressing Endocrine Cells in Children With Type 1 Diabetes

It has been proposed that the deficit in β-cell mass in type 1 diabetes (T1D) may be due, in part, to β-cell degranulation to chromogranin-positive hormone-negative (CPHN) cells. The frequency and distribution of pancreatic CPHN cells were investigated in 19 children with T1D compared with 14 nondiabetic (ND) children. We further evaluated these cells for replication and expression of endocrine lineage markers Nkx6.1 and Nkx2.2, and compared these frequencies with those previously reported in CPHN cells in adults with T1D. In contrast to adults’ cells, pancreatic CPHN cells were comparably abundant (percentage of endocrine cells ± standard error of the mean, 1.4 ± 0.2 vs 1.0 ± 0.2 in patients with T1D vs ND subjects, respectively; P = not significant) and comparably distributed in children with T1D vs ND donors. Replication of CPHN cells was detected but unchanged in children with T1D vs ND children, as was the percentage of CPHN cells expressing Nkx6.1 or NKx2.2. In children with T1D, the frequency of pancreatic CPHN cells was not increased, and this differed from adults with T1D.

Increased Frequency of Hormone Negative and Polyhormonal Endocrine Cells in Lean Individuals With Type 2 Diabetes

CONTEXT

It has been suggested that beta cell loss in type 2 diabetes (T2D) may be due to beta cell degranulation and/or altered cell identity. While shown to have a minor role in obese T2D, this has not been evaluated in lean T2D.

OBJECTIVE

To establish the contribution of altered beta cell identity in lean T2D and, using a rodent model of lean T2D, whether changes in beta cell identity precede hyperglycemia.

DESIGN, SETTING, AND PARTICIPANTS

We investigated the frequency of chromogranin A positive hormone negative (CPHN) and polyhormonal endocrine cells in pancreas from 10 lean nondiabetic and 10 lean T2D subjects and in pancreas from wild-type and human IAPP transgenic rats at the prediabetic and diabetic stages.

RESULTS

CPHN cells and polyhormonal-expressing cells were comparably increased in lean T2D and human IAPP transgenic rats, in the latter both before and at onset of diabetes. However, the extent of these cells could only account for approximately 2% of beta cell loss.

CONCLUSION

Degranulation and altered identity play at most a minor role in the beta cell deficit in lean T2D. Because the increase in CPHN and polyhormonal cells precede diabetes onset, these changes are likely a response to stress rather than hyperglycemia, and may reflect attempted regeneration.

Increased Hormone-Negative Endocrine Cells in the Pancreas in Type 1 Diabetes

CONTEXT AND OBJECTIVE

Type 1 diabetes (T1D) is characterized by a β-cell deficit due to autoimmune inflammatory-mediated β-cell destruction. It has been proposed the deficit in β-cell mass in T1D may be in part due to β-cell degranulation to chromogranin-positive, hormone-negative (CPHN) cells.

DESIGN, SETTING, AND PARTICIPANTS

We investigated the frequency and distribution of CPHN cells in the pancreas of 15 individuals with T1D, 17 autoantibody-positive nondiabetic individuals, and 17 nondiabetic controls.

RESULTS

CPHN cells were present at a low frequency in the pancreas from nondiabetic and autoantibody-positive, brain-dead organ donors but are more frequently found in the pancreas from donors with T1D (islets: 1.11% ± 0.20% vs 0.26% ± 0.06 vs 0.27% ± 0.10% of islet endocrine cells, T1D vs autoantibody positive [AA+] vs nondiabetic [ND]; T1D vs AA+, and ND, P < .001). CPHN cells are most commonly found in the single cells and small clusters of endocrine cells rather than within established islets (clusters: 18.99% ± 2.09% vs 9.67% ± 1.49% vs 7.42% ± 1.26% of clustered endocrine cells, T1D vs AA+ vs ND; T1D vs AA+ and ND, P < .0001), mimicking the distribution present in neonatal pancreas.

CONCLUSIONS

From these observations, we conclude that CPHN cells are more frequent in T1D and, as in type 2 diabetes, are distributed in a pattern comparable with the neonatal pancreas, implying a possible attempted regeneration. In contrast to rodents, CPHN cells are insufficient to account for loss of β-cell mass in T1D.

CHOP Contributes to, But Is Not the Only Mediator of, IAPP Induced β-Cell Apoptosis

The islet in type 2 diabetes is characterized by β-cell loss, increased β-cell apoptosis, and islet amyloid derived from islet amyloid polypeptide (IAPP). When protein misfolding protective mechanisms are overcome, human IAPP (h-IAPP) forms membrane permeant toxic oligomers that induce β-cell dysfunction and apoptosis. In humans with type 2 diabetes (T2D) and mice transgenic for h-IAPP, endoplasmic reticulum (ER) stress has been inferred from nuclear translocation of CCAAT/enhancer-binding protein homologous protein (CHOP), an established mediator of ER stress. To establish whether h-IAPP toxicity is mediated by ER stress, we evaluated diabetes onset and β-cell mass in h-IAPP transgenic (h-TG) mice with and without deletion of CHOP in comparison with wild-type controls. Diabetes was delayed in h-TG CHOP(-/-) mice, with relatively preserved β-cell mass and decreased β-cell apoptosis. Deletion of CHOP attenuates dysfunction of the autophagy/lysosomal pathway in β-cells of h-TG mice, uncovering a role for CHOP in mediating h-IAPP-induced dysfunction of autophagy. As deletion of CHOP delayed but did not prevent h-IAPP-induced β-cell loss and diabetes, we examined CHOP-independent stress pathways. JNK, a target of the IRE-1pTRAF2 complex, and the Bcl-2 family proapoptotic mediator BIM, a target of ATF4, were comparably activated by h-IAPP expression in the presence and absence of CHOP. Therefore, although these studies affirm that CHOP is a mediator of h-IAPP-induced ER stress, it is not the only one. Therefore, suppression of CHOP alone is unlikely to be a durable therapeutic strategy to protect against h-IAPP toxicity because multiple stress pathways are activated.

β-Cell Deficit in Obese Type 2 Diabetes, a Minor Role of β-Cell Dedifferentiation and Degranulation

CONTEXT

Type 2 diabetes is characterized by a β-cell deficit and a progressive defect in β-cell function. It has been proposed that the deficit in β-cells may be due to β-cell degranulation and transdifferentiation to other endocrine cell types.

OBJECTIVE

The objective of the study was to establish the potential impact of β-cell dedifferentiation and transdifferentiation on β-cell deficit in type 2 diabetes and to consider the alternative that cells with an incomplete identity may be newly forming rather than dedifferentiated.

DESIGN, SETTING, AND PARTICIPANTS

Pancreata obtained at autopsy were evaluated from 14 nondiabetic and 13 type 2 diabetic individuals, from four fetal cases, and from 10 neonatal cases.

RESULTS

Whereas there was a slight increase in islet endocrine cells expressing no hormone in type 2 diabetes (0.11 ± 0.03 cells/islet vs 0.03 ± 0.01 cells/islet, P < .01), the impact on the β-cell deficit would be minimal. Furthermore, we established that the deficit in β-cells per islet cannot be accounted for by an increase in other endocrine cell types. The distribution of hormone negative endocrine cells in type 2 diabetes (most abundant in cells scattered in the exocrine pancreas) mirrors that in developing (embryo and neonatal) pancreas, implying that these may represent newly forming cells.

CONCLUSIONS

Therefore, although we concur that in type 2 diabetes there are endocrine cells with altered cell identity, this process does not account for the deficit in β-cells in type 2 diabetes but may reflect, in part, attempted β-cell regeneration.

[The monaural pseudo-stereophonic hearing aid (BAHA) in unilateral total deafness: a study of 29 patients]

For many years, unilateral total deafness has been considered a minor handicap which does not require the fitting of a hearing aid. If the condition did give a major problem, the usual recommendation for this type of hearing loss was a CROS system which, in addition to problems of function and aesthetics, gave poor results. Faced with increasing demands from these patients, and given the good performance of bone conduction implants (BAHA), we decided to try to implant these devices on the deaf side, which allowed, by way of transcranial conduction, stimulation of the functioning ear and the re-establishment of a certain degree of stereophonic hearing. This study of 29 patients who were tested by stereophonic audiometry pre- and post-implantation shows that this type of aiding is beneficial, with improvement of the threshold of intelligibility against background noise of between 5 and 15 dB during Hirsch's test, correction of the "dead angle" on the deaf side, and improvement in localisation of sound in space. From the functional point of view, 88% of patients were satisfied with their aid, which they wore for 8 or 9 hours per day, and had a marked improvement in their hearing performance under various conditions which had proved very difficult for them before they were fitted with the aid. These results all demonstrate the effectiveness of the implant used in this way. The fact that sounds are received on the totally deaf side goes a long way towards establishing satisfactory hearing. True stereophonic hearing could not be established in any of the cases, because this requires input from two ears. It is for this reason that we have termed this type of aid as monaural pseudo-stereophonic.

Structural determinants for potent, selective dual site inhibition of human pp60c-src by 4-anilinoquinazolines

The kinetic mechanisms for the inhibition of pp60(c-src) tyrosine kinase (Src TK) by 4-anilinoquinazolines, an important class of chemicals as protein kinase inhibitors, were investigated. 4-Anilinoquinazolines with a bulky group at the 4'-position of the anilino group were shown to be competitive with both ATP and peptide, whereas molecules lacking such a bulky group only displayed an inhibition pattern typical of those competitive with ATP and noncompetitive with peptide. Modifications of the substituents on the carbocyclic ring did not perturb the inhibition pattern although the affinities of these modified inhibitors for Src TK were affected. Structural modeling of Src TK with inhibitor and peptide substrate bound indicated a direct atomic conflict between the bulky 4-position group and the hydroxy of the peptide tyrosyl to which the gamma-phosphate of ATP is transferred during the kinase reaction. This atomic conflict would likely prevent simultaneous binding of both inhibitor and peptide, consistent with the observed kinetic competitiveness of the inhibitor with peptide. The dual site inhibitors appeared to have both enhanced potency and selectivity for Src TK. One such inhibitor, 4-(4'-phenoxyanilino)-6,7-dimethoxyquinazoline, had a 15 nM potency against Src TK and was selective over receptor tyrosine kinases VEGFR2 by 88-fold and C-fms by 190-fold.

The discovery of potent cRaf1 kinase inhibitors

A series of benzylidene-1H-indol-2-one (oxindole) derivatives was synthesized and evaluated as cRaf-1 kinase inhibitors. The key features of the molecules were the donor/acceptor motif common to kinase inhibitors and a critical acidic phenol flanked by two substitutions. Diverse 5-position substitutions provided compounds with low nanomolar kinase enzyme inhibition and inhibited the intracellular MAPK pathway.

Antibody-directed enzyme prodrug therapy with the T268G mutant of human carboxypeptidase A1: in vitro and in vivo studies with prodrugs of methotrexate and the thymidylate synthase inhibitors GW1031 and GW1843

Antibody-directed enzyme prodrug therapy (ADEPT) is a technique to increase antitumor selectivity in cancer chemotherapy. Our approach to this technology has been to design a mutant of human carboxypeptidase A (hCPA1-T268G) which is capable of hydrolyzing in vivo stable prodrugs of MTX and targeting this enzyme to tumors on an Ep-CAM1-specific antibody, ING1. Through the use of this >99% human enzyme which is capable of catalyzing a completely nonhuman reaction, we hope to increase ADEPT selectivity while decreasing overall immunogenicity of the enzyme-antibody conjugate. In the current report, prodrugs of the thymidylate synthase inhibitors GW1031 and GW1843 and the dihydrofolate reductase inhibitor methotrexate were studied for their wild-type and mutant hCPA enzyme hydrolysis, their in vivo stability, and their use in therapy. Prodrugs with high kcat/Km ratios for mutated versus wild-type hCPA1 were examined in vitro for their stability in human pancreatic juice, and in vivo for their stability in mouse plasma and tissues. In addition, targeting and in vivo enzyme activity studies were performed with an ING1 antibody conjugate of the mutant enzyme (ING1-hCPA1-T268G). Finally, in vivo therapy studies were performed with LS174T tumors to demonstrate proof of principle. Results indicate that prodrugs can be synthesized that are selective and efficient substrates of hCPA1-T268G and not substrates of the endogenous CPA activities; this leads to excellent in vivo stability for these compounds. In vivo conjugate targeting studies showed that the antibody-enzyme conjugate was targeted to the tumor and enzyme was initially active in vivo at the site. Unfortunately therapeutic studies did not demonstrate tumor reduction. Experiments to determine reasons for the lack of antitumor activity showed that the enzyme activity decreased as a result of enzyme instability. The results offer encouragement for additional novel mutant enzyme improvements and additional in vivo studies on this unique approach to ADEPT.

Constant temperature monitoring: a study of temperature patterns in the postanesthesia care unit

Patients admitted to the PACU from the operating room exhibit fluctuations in core body temperature during the course of their stay in the PACU. Some patients present with normothermia and experience temperature decreases later in their stay. PACU policy does not dictate that temperatures be measured at a predetermined frequency in the absence of hypothermia; thus, it is possible that hypothermia may not be detected at its onset. The major purpose of this study was to describe the core body temperature patterns of postsurgical patients during the PACU stay. Secondary objectives were to (1) identify at which point in time patients become hypothermic and (2) describe length of stay in patients who develop hypothermia. Hypothermia was defined as a core tympanic temperature of less than 35.5 degrees C. A descriptive design was used using a convenience sample of 150 elective surgical patients over the age of 1 month who were normothermic on admission to the PACU. Data were analyzed using descriptive statistics. Concurrent tympanic and continuous axillary temperatures were monitored for comparison and trend monitoring. Temperatures showed clinically significant decreases into the hypothermic range (< 35.5 degrees C). Fifty-seven percent of the sample (n = 86) had temperatures that dropped after PACU admission and another 13% fell below 35.5 degrees C. Hypothermia occurred within the first 15 minutes of the PACU stay. The average length of stay for those that developed hypothermia was 1.83 hours. Monitoring temperatures more frequently will result in detecting hypothermia at its onset. Nurses may use the axillary device as a trend for continuous monitoring. Length of stay may be shortened if temperature management is embraced by the PACU nurse.

Toward antibody-directed enzyme prodrug therapy with the T268G mutant of human carboxypeptidase A1 and novel in vivo stable prodrugs of methotrexate

Antibody-directed enzyme prodrug therapy (ADEPT) has the potential of greatly enhancing antitumor selectivity of cancer therapy by synthesizing chemotherapeutic agents selectively at tumor sites. This therapy is based upon targeting a prodrug-activating enzyme to a tumor by attaching the enzyme to a tumor-selective antibody and dosing the enzyme-antibody conjugate systemically. After the enzyme-antibody conjugate is localized to the tumor, the prodrug is then also dosed systemically, and the previously targeted enzyme converts it to the active drug selectively at the tumor. Unfortunately, most enzymes capable of this specific, tumor site generation of drugs are foreign to the human body and as such are expected to raise an immune response when injected, which will limit their repeated administration. We reasoned that with the power of crystallography, molecular modeling and site-directed mutagenesis, this problem could be addressed through the development of a human enzyme that is capable of catalyzing a reaction that is otherwise not carried out in the human body. This would then allow use of prodrugs that are otherwise stable in vivo but that are substrates for a tumor-targeted mutant human enzyme. We report here the first test of this concept using the human enzyme carboxypeptidase A1 (hCPA1) and prodrugs of methotrexate (MTX). Based upon a computer model of the human enzyme built from the well known crystal structure of bovine carboxypeptidase A, we have designed and synthesized novel bulky phenylalanine- and tyrosine-based prodrugs of MTX that are metabolically stable in vivo and are not substrates for wild type human carboxypeptidases A. Two of these analogs are MTX-alpha-3-cyclobutylphenylalanine and MTX-alpha-3-cyclopentyltyrosine. Also based upon the computer model, we have designed and produced a mutant of human carboxypeptidase A1, changed at position 268 from the wild type threonine to a glycine (hCPA1-T268G). This novel enzyme is capable of using the in vivo stable prodrugs, which are not substrates for the wild type hCPA1, as efficiently as the wild type hCPA1 uses its best substrates (i.e. MTX-alpha-phenylalanine). Thus, the kcat/Km value for the wild type hCPA1 with MTX-alpha-phenylalanine is 0.44 microM-1 s-1, and kcat/Km values for hCPA1-T268G with MTX-alpha-3-cyclobutylphenylalanine and MTX-alpha-3-cyclopentyltyrosine are 1.8 and 0.16 microM-1 s-1, respectively. The cytotoxic efficiency of hCPA1-268G was tested in an in vitro ADEPT model. For this experiment, hCPA1-T268G was chemically conjugated to ING-1, an antibody that binds to the tumor antigen Ep-Cam, or to Campath-1H, an antibody that binds to the T and B cell antigen CDw52. These conjugates were then incubated with HT-29 human colon adenocarcinoma cells (which express Ep-Cam but not the Campath 1H antigen) followed by incubation of the cells with the in vivo stable prodrugs. The results showed that the targeted ING-1:hCPA1-T268G conjugate produced excellent activation of the MTX prodrugs to kill HT-29 cells as efficiently as MTX itself. By contrast, the enzyme-Campath 1H conjugate was without effect. These data strongly support the feasibility of ADEPT using a mutated human enzyme with a single amino acid change.

Expression and characterization of human pancreatic preprocarboxypeptidase A1 and preprocarboxypeptidase A2

We are investigating the potential utility of human carboxypeptidases A in antibody-directed enzyme prodrug therapy (ADEPT). Hybridization screening of a human pancreatic cDNA library with cDNA probes that encoded either rat carboxypeptidase A1 (rCPA1) or carboxypeptidase A2 (rCPA2) was used to clone the human prepro-CPA homologs. After expression of the respective pro-hCPA cDNA in Saccharomyces cerevisiae, the enzymes were purified to homogeneity by a combination of hydrophobic and ion-exchange chromatography. Purified hCPA1 and hCPA2 migrate as a single protein band with M(r) 34,000 when subjected to gel electrophoresis in the presence of sodium dodecyl sulfate under reducing conditions. Kinetic studies of the purified enzymes with hippuryl-L-phenylalanine resulted in kcat/Km values of 57,000 and 19,000 M-1 s-1 for hCPA1 and hCPA2, respectively. Using the ester substrate, hippuryl-D, L-phenyllactate, we found unique esterase/ peptidase specific activity ratios among hCPA1, hCPA2, rCPA1, and bovine CPA (bCPA) ranging from 13 to 325. Two potential ADEPT substrates, methotrexate-alpha-phenylalanine (MTX-Phe) and methotrexate-alpha-(1-naphthyl)alanine (MTX-naphthylAla) were also analyzed. The kcat/Km values for MTX-Phe were 440,000 and 90,000 M-1 s-1 for hCPA1 and hCPA2, respectively, and for MTX-naphthylAla these values were 1400 and 1,400,000 M-1 s-1 for hCPA1 and hCPA2, respectively. The kinetic data show that hCPA2 has a larger substrate binding site than the hCPA1 enzyme. Differences between hCPA1 and hCPA2 were also observed in thermal stability experiments at 60 degrees C where the half-life for thermal denaturation of hCPA2 is eightfold longer than that for hCPA1. These experiments indicate that hCPA1 and hCPA2 are potential candidates for use in a human-based ADEPT approach.

Molecular diversity in chemical databases: comparison of medicinal chemistry knowledge bases and databases of commercially available compounds

A molecular descriptor space has been developed which describes structural diversity. Large databases of molecules have been mapped into it and compared. This analysis used five chemical databases, CMC and MDDR, which represent knowledge bases containing active medicinal agents, ACD and SPECS, two databases of commercially available compounds, and finally the Wellcome Registry. Together these databases contained more than 300,000 structures. Topological indices and the free energy of solvation were computed for each compound in the databases. Factor analysis was used to reduce the dimensionality of the descriptor space. Low density observations were deleted as a way of removing outliers, which allowed a further reduction in the descriptor space of interest. The five databases could then be compared on an efficient basis using a metric developed for this purpose. A Riemann gridding scheme was used to subdivide the factor space into subhypercubes to obtain accurate comparisons. Most of the 300,000 structures were highly clustered, but unique structures were found. An analysis of overlap between the biological and commercial databases was carried out. The metric provides a useful algorithm for choosing screening sets of diverse compounds from large databases.

Structure-activity relationship of novel pentapeptide neuropeptide Y receptor antagonists is consistent with a noncontinuous epitope for ligand-receptor binding

We report the first systematic study on short peptide structure affinity and activity for the neuropeptide Y (NPY) receptor. A series of linear pentapeptides has been synthesized that display affinities in the low micromolar range toward rat brain NPY receptors. Furthermore, some of these compounds competitively antagonize the Y1-type NPY receptor-mediated increase in cytosolic Ca2+ in human erythroleukemic (HEL) cells. The inactive NPY carboxyl-terminal pentapeptide (Thr-Arg-Gln-Arg-Tyr-NH2; IC50 > 100 microM) was modified by replacing threonine with an aromatic amino acid and glutamine with leucine. This resulted in a series of pentapeptides with dramatically improved affinity (IC50 = 0.5-4 microM) for the rat brain receptor. The structure-affinity data suggest that these peptides may represent a noncontinuous epitope containing the amino-terminal tyrosine and the carboxyl-terminal residues Arg-35 and Tyr-36 of NPY.

Structure-activity studies of dicationically substituted bis-benzimidazoles against Giardia lamblia: correlation of antigiardial activity with DNA binding affinity and giardial topoisomerase II inhibition

Nine dicationically substituted bis-benzimidazoles were examined for their in vitro activities against Giardia lamblia WB (ATCC 30957). The potential mechanisms of action of these compounds were evaluated by investigating the relationship among in vitro antigiardial activity and the affinity of the molecules for DNA and their ability to inhibit the activity of giardial topoisomerase II. Each compound demonstrated antigiardial activity, as measured by assessing the incorporation of [methyl-3H]thymidine by giardial trophozoites exposed to the test agents. Three compounds exhibited excellent in vitro antigiardial activities, with 50% inhibitory concentrations which compared very favorably with those of two currently used drugs, quinacrine HCl and metronidazole. Putative mechanisms of action for these compounds were suggested by the strong correlation observed among in vitro antigiardial activity and the affinity of the molecules for natural and synthetic DNA and their ability to inhibit the relaxation activity of giardial topoisomerase II. A strong correlation between the DNA binding affinity of these compounds and their inhibition of giardial topoisomerase II activity was also observed.

Structure, DNA minor groove binding, and base pair specificity of alkyl- and aryl-linked bis(amidinobenzimidazoles) and bis(amidinoindoles)

A series of bis(amidinobenzimidazoles) and bis(amidinoindoles) with varied linking chains connecting the aromatic groups and various modifications to the basic amidino groups have been prepared. The calf thymus (CT) DNA and nucleic acid homopolymer [poly(dA).poly(dT),poly(dA-dT).poly-(dA-dT), and poly(dG-dC).poly(dG-dC)] binding properties of these compounds have been studied by thermal denaturation (delta Tm) and viscosity. The compounds show a greater affinity for poly(dA).poly(dT) and poly(dA-dT).poly(dA-dT) than for poly(dG-dC).poly(dG-dC). Viscometric titrations indicate that the compounds do not bind by intercalation. Molecular modeling studies and the biophysical data suggest that the molecules bind to the minor groove of CT DNA and homopolymers. Analysis of the shape of the molecules is consistent with this mode of nucleic acid binding. Compounds with an even number of methylenes connecting the benzimidazole rings have a higher affinity for DNA than those with an odd number of methylenes. Molecular modeling calculations that determine the radius of curvature of four defined groups in the molecule show that the shape of the molecule, as a function of chain length, affects the strength of nucleic acid binding. Electronic effects from cationic substituents as well as hydrogen bonding from the imidazole nitrogens also contribute to the nucleic acid affinity. The bis(amidinoindoles) show no structurally associated differential in nucleic acid base pair specificity or affinity.

Structure and DNA binding activity of analogues of 1,5-bis(4-amidinophenoxy)pentane (pentamidine)

The DNA binding properties of a series of 39 bisbenzamidines related to the clinically used antipneumocystis drug pentamidine (1) were studied. Changes in the thermal denaturation temperature of calf thymus DNA (delta Tm) showed that all the compounds have significant affinity for DNA. A comparison of delta Tms for the series with delta Tms of base-pair-specific DNA-binding compounds, using homopolymers poly(dA).poly(dT) and poly(dG-dC).poly(dG-dC), indicated that the compounds show moderate specificity for AT base pairs. Lack of DNA helix extension, measured by viscometric titration with sonicated calf thymus DNA, indicated that the compounds do not bind to DNA by intercalation. Analogues of 1 with an odd number of methylenes connecting the benzamidine rings had a higher affinity for DNA and homopolymers than analogues with an even number of methylenes. All of the compounds containing an amidino group meta to the linking chain showed lower polynucleotide affinity. These results suggest that the shape of the molecules was important for DNA binding. Molecular modeling studies showed a correlation between the DNA binding and the radius of curvature of molecular mechanics models of the molecules. Monosubstitution on the benzamidine rings or replacement of the amidino group with the cyclic imidazolino group had no influence on the DNA-binding affinity of the compounds. Substitution of NH for the ether oxygen connecting group of 1 had no effect on the DNA binding or base-pair specificity. Methylation of either of the nitrogen atoms of the imidazolino group to provide an analogue of 1 with N-methylimidazolino groups decreased DNA affinity considerably. GC vs AT base-pair specificity as measured by delta Tm does not correlate with the radius of curvature. The experimental and modeling results are consistent with DNA minor-groove binding.

2-[(arylmethyl) amino]-2-methyl-1,3-propanediol DNA intercalators. An examination of the effects of aromatic ring variation on antitumor activity and DNA binding

The effects of variation of aromatic ring size, shape, and side-chain position on antitumor activity and DNA binding in a series of carbocyclic 2-[(arylmethyl)amino]-2-methyl-1,3-propanediols (AMAPs) were examined. In general, the interaction of AMAPs with DNA increases as the intercalating ring system grows in area, with three distinct binding levels evident. Isomers from a specific ring system appear to bind DNA similarly. DNA binding is not the sole criterion for antitumor activity for the AMAPs studied; the magnitude of the delta Tm does not correlate with the antitumor activity observed. Significant in vivo P388 activity was seen for AMAP congeners from several tetracyclic ring systems. However, isomers from each of the specific ring systems produced a wide range of in vivo P388 activity. Thus, AMAP antitumor activity is not a function of the ring system per se, but rather appears to be related to the shape of the specific molecule. Three AMAP congeners (crisnatol (770U82, 773U82, and 502U83) are currently in clinical trials.

Structure-activity relationships of pentamidine analogs against Giardia lamblia and correlation of antigiardial activity with DNA-binding affinity

1,5-Di(4-amidinophenoxy)pentane (pentamidine) and 38 analogs of pentamidine were screened for in vitro activity against the enteric protozoan Giardia lamblia WB (ATCC 30957). All compounds were active against G. lamblia as measured by a [methyl-3H]thymidine incorporation assay. Antigiardial activity varied widely, with 50% inhibitory concentrations (IC50s) ranging from 0.51 +/- 0.13 microM (mean +/- standard deviation) for the most active compound to over 100.0 microM for the least active compounds. The IC50 of the most potent antigiardial agent, 1,3-di(4-amidino-2-methoxyphenoxy)propane compared favorably with the IC50s of the compounds currently used to treat giardiasis, i.e., furazolidone (1.0 +/- 0.03 microM), metronidazole (2.1 +/- 0.80 microM), quinacrine HCl (0.03 +/- 0.02 microM), and tinidazole (0.78 +/- 0.48 microM). A mode of antigiardial activity for these compounds was suggested by the correlation observed between antigiardial activity and the binding of the compounds to calf thymus DNA and poly(dA).poly(dT).

Interaction of a macrocyclic bisacridine with DNA

The binding of the macrocycle SDM to DNA was investigated by visible spectroscopy, stopped-flow kinetics, and NMR spectroscopy. SDM is composed of two 9-aminoacridines linked via the amino groups by a spermine side chain and via the 4-positions by a N,N'-[(methylthio)ethyl]succinamide side chain [Zimmerman, S. C., Lamberson, C. R., Cory, M., & Fairley, T. A. (1989) J. Am. Chem. Soc. 111, 6805-6809]. The visible spectrum of SDM bound to poly[d(A-T)]2 or poly[d(G-C)]2 is red-shifted relative to the spectrum of SDM alone and displays considerable hypochromicity. Results from titrations of SDM with polymer indicate a binding site size of three base pairs per macrocycle. The dissociation constant for SDM bound to either poly[d(A-T)]2 or poly[d(G-C)]2 is an order of magnitude lower than that for a similar bisacridine linked only by a spermine side chain. In addition, the dependence of the dissociation constant on ionic strength is significantly reduced. NMR studies of SDM complexes with poly[d(A-T)]2 or a tetramer, d(CGCG)2, show that intercalation is the mode of binding. The magnitudes of the chemical shift differences for SDM aromatic protons in the free and bound states support intercalation with the acridine ring systems essentially parallel to the long axis of the base pairs. Cross peaks from NOESY spectra of the SDM complex with d(CGCG)2 further support this mode of binding and provide information on the structure of the complex. The results are analyzed for consistency with each of three binding models: (i) bisintercalation with the two side chains in the same groove; (ii) bisintercalation according to the neighbor-exclusion principle with the two side chains in opposite grooves; and (iii) bisintercalation with two side chains in opposite grooves but with violation of the neighbor-exclusion principle. Model i is found to be unlikely on the basis of all evidence obtained, including preliminary modeling studies. Both models ii and iii can be reconciled with the experimental evidence and from a modeling standpoint are energetically feasible.

(1-Pyrenylmethyl)amino alcohols, a new class of antitumor DNA intercalators. Discovery and initial amine side chain structure-activity studies

In the series of 1-pyrenylmethylamines studied in this work the relationships among structure, interaction with DNA, and murine antitumor activity were examined. Binding studies show that all of these 1-pyrenylmethylamine derivatives bind to some extent to DNA by intercalation. The presence of additional basic amine groups in the side chain enhances DNA binding due to electrostatic interactions. Those compounds containing only a single basic benzylic amine bind similarly to DNA. Only the presence of bulky side chains appears to decrease the DNA interactions in the compounds examined. Although antitumor activity is seen for (1-pyrenylmethyl)amino alcohols, useful antitumor activity in the series is limited to those congeners bearing the 2-amino-1,3-propanediol-type side chain. These derivatives bind moderately to DNA. DNA binding is a necessary but not sufficient criterion for antitumor activity in the series. In addition, the strength of DNA binding does not correlate with the antitumor activity in the group of active compounds. Three related 2-[(arylmethyl)amino]-1,3-propanediol derivatives (AMAPs) [crisnatol (770U82), 773U82, and 502U83] are currently in clinical trials as potential antitumor agents.

Analogues of 1,5-bis(4-amidinophenoxy)pentane (pentamidine) in the treatment of experimental Pneumocystis carinii pneumonia

A series of 33 analogues of the anti-Pneumocystis carinii drug 1,5-bis(4-amidinophenoxy)pentane (pentamidine) was synthesized for screening against a rat model of P. carinii pneumonia (PCP). Twenty-five of the compounds showed efficacy against PCP when compared to a saline-treated control group. Two compounds, 1,4-bis(4-amidinophenoxy)butane (butamidine, 6) and 1,3-bis(4-amidino-2-methoxyphenoxy)propane (DAMP, 16), were statistically more effective than the parent drug in treating PCP in the rat model of infection. In addition to their activity against PCP, the compounds were also evaluated for antitrypsin activity, ability to inhibit thymidylate synthetase, affinity for DNA, and toxicity. No correlation was observed between the tested molecular interactions of the diamidines and their effectiveness against PCP.

Conformational analysis and molecular modeling of 1-phenyl-, 4-phenyl-, and 1-benzyl-1,2,3,4-tetrahydroisoquinolines as D1 dopamine receptor ligands

Conformational studies on a series of 1-phenyl-, 4-phenyl-, and 1-benzyl-1,2,3,4-tetrahydroisoquinolines that possess an identical substituent pattern to the prototypical D1 dopamine receptor antagonist SCH23390 [(R)-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5- tetrahydro-1H-3-benzazepine (1)] were performed with use of molecular mechanics calculations [MM2(85), with newly developed aromatic halide bending and torsional parameters that are now incorporated into MM2(87)], single-crystal X-ray analysis, and high-field NMR spectroscopy. The synthesis and biological testing of compounds 2-7 has been previously reported. The test compounds were compared both quantitatively and graphically to compound 1. Calculations on both the free-base and protonated forms of each compound were carried out. To insure that conformation space was adequately sampled, the test compounds were energy minimized from different starting geometries; ring inversion of the heterocycle was employed, as were dihedral driver calculations on the phenyl or benzyl rings. For N-methyl-6-chloro-7-hydroxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline (2), it was determined that the torsion angle tau(C8a-C1-C12-C17) had energy minima at approximately 60 degrees and 240 degrees. This finding was corroborated by NMR studies that indicated a dramatic upfield chemical shift of ArH8 after ring cyclization. The nitrogen lone pair or hydrogen vector was approximately orthogonal to the plane of the substituted aromatic ring in the tetrahydroisoquinolines; this explained the upfield chemical shift of the vicinal chiral proton (H1). In all instances, the 6-membered heterocyclic ring in the energy-minimized structures preferred the half-chair conformation with the phenyl rings pseudo-equatorial. Distance comparisons of the proposed pharmacophoric atoms (Cl, N, O, centroid of the phenyl or benzyl ring) showed that the phenyl or benzyl centroid to ammonium H distance, Cl to N distance, and distance of the nitrogen above or below the plane of the isoquinoline aromatic ring are the distances most highly correlated with biological activity (r = 0.82, 0.75, 0.81, respectively). Resolution and single-crystal X-ray analysis of compound 2 showed the most active enantiomer to possess the S absolute configuration, in contrast to the benzazepine (R)-1. Least-squares fitting of the energy-minimized structures with SYBYL molecular modeling software showed (S)-(+)-2, rather than (R)-(-)-2, gave a better fit to (R)-1. Volume determinations derived from SYBYL multifit analyses aided in receptor mapping to qualitatively describe areas of "active" pharmacophore space as well as areas of "inactive" substituent space.(ABSTRACT TRUNCATED AT 400 WORDS)

DNA intercalation and inhibition of topoisomerase II. Structure-activity relationships for a series of amiloride analogs

Among its many properties, amiloride is a DNA intercalator and topoisomerase II inhibitor. Previous work has indicated that the most stable conformation for amiloride is a planar, hydrogen-bonded, tricyclic structure. To determine whether the ability of amiloride to intercalate into DNA and to inhibit DNA topoisomerase II was dependent on the ability to assume a cyclized conformation, we studied the structure-activity relationship for 12 amiloride analogs. These analogs contained structural modifications which could be expected to allow or impede formation of a cyclized conformation. Empirical assays consisting of biophysical, biochemical, and cell biological approaches, as well as computational molecular modeling approaches, were used to determine conformational properties for these molecules, and to determine whether they intercalated into DNA and inhibited topoisomerase II. Specifically, we measured the ability of these compounds to 1) alter the thermal denaturation profile of DNA, 2) modify the hydrodynamic behavior of DNA, 3) inhibit the catalytic activity of purified DNA topoisomerase II in vitro, 4) promote the topoisomerase II-dependent cleavage of DNA, and 5) inhibit functions associated with DNA topoisomerase II in intact cells. Results indicated that only those analogs capable of cyclization could intercalate into DNA and inhibit topoisomerase II. Thus, the ability of amiloride and the 12 analogs studied to intercalate into DNA and to inhibit topoisomerase II appears dependent on the ability to exist in a planar, hydrogen-bonded, tricyclic conformation.

Amiloride intercalates into DNA and inhibits DNA topoisomerase II

Amiloride is capable of inhibiting DNA synthesis in mammalian cells in culture. Recent evidence indicates that the enzyme, DNA topoisomerase II, is probably required for DNA synthesis to occur in situ. In experiments to determine the mechanism of inhibition of DNA synthesis by amiloride, we observed that amiloride inhibited both the catalytic activity of purified DNA topoisomerase II in vitro and DNA topoisomerase II-dependent cell functions in vivo. Many compounds capable of inhibiting DNA topoisomerase II are DNA intercalators. Thus, we performed studies to determine if and how amiloride bound to DNA. Results indicated that amiloride 1) shifted the thermal denaturation profile of DNA, 2) increased the viscosity of linear DNA, and 3) unwound circular DNA, all behavior consistent with a DNA intercalation mechanism. Furthermore, quantitative and qualitative measurements of amiloride fluorescence indicated that amiloride (a) bound reversibly to purified DNA under conditions of physiologic ionic strength, and (b) bound to purified nuclei in a highly cooperative manner. Lastly, amiloride did not promote the cleavage of DNA in the presence of DNA topoisomerase II, indicating that the mechanism by which amiloride inhibited DNA topoisomerase II was not through the stabilization of a "cleavable complex" formed between DNA topoisomerase II, DNA, and amiloride. The ability of amiloride to intercalate with DNA and inhibit topoisomerase II is consistent with the proposed planar, hydrogen-bonded, tricyclic nature of amiloride's most stable conformation. Thus, DNA and DNA topoisomerase II must be considered as new cellular targets of amiloride action.

Nephrogenic diabetes insipidus. Radiological and clinical features

Two brothers with nephrogenic diabetes insipidus are presented. The importance of early recognition and treatment to reverse the consequential complications are underscored. The disorder has a sex-linked recessive transmission, where all male offspring of an affected mother show the extreme thirst characteristic of the disease; in whom hyposthenuria persisted despite arginine vasopressin infusion, and in whom the serum arginine vasopressin concentrations correlate with the serum osmolality which serves to discriminate nephrogenic diabetes insipidus from the pituitary diabetes insipidus. The radiological features of "non-obstructive" hydronephrosis and hydroureters, the combined use of hydrochlorothiazide and the potassium-sparing diuretic amiloride in comparison to the prostaglandin inhibitor are discussed.

Antitumor anthracycline antibiotics. Structure-activity and structure-cardiotoxicity relationships of rubidazone analogues

A series of rubidazone analogues (4-14) with varying phenyl group substituents was prepared. The effect of these compounds on inhibition of nucleic acid synthesis in cultured cells, on in vivo antitumor properties, and on cardiotoxicity was examined. Substituent effects on drug-DNA binding as indicated by DNA melting temperature measurements were also investigated. Substituent effects were essentially absent among the rubidazone analogues in in vivo and in vitro test systems which measure cytotoxic characteristics; however, the rubidazone analogues varied substantially in their cardiotoxic effects and this variation was closely correlated with the electronic character of the phenyl substituent.

Antifilarial agents. 3-Aminopyrrolidine and 1,4-diazabicyclo[3.2.1]octane derivatives as analogues of diethylcarbamazine

3-Aminopyrrolidines bearing acyl substituents on either nitrogen and N-acylated 1,4-diazabicyclo[3.2.1]octanes are potent microfilaricides in the Litomosoides carinii gerbil test system but have no effect on adult worms. The high activity of the pyrrolidine derivatives establishes that diethylcarbamazine (DEC) like antifilarial activity does not require that both pharmacophores be incorporated into one ring. Results with the 1,4-diazabicyclo[3.2.1]octanes establish that an axial conformation of the alkyl substituent corresponding to the equatorial N-methyl group of diethylcarbamazine is fully consistent with high activity. Other conformational consideration pertinent to DEC analogues are discussed.

Inhibition of C1s-induced vascular leakage in guinea pigs by substituted benzamidine and pyridinium compounds

A variety of benzamidine and pyridinium compounds were examined for their ability to inhibit irreversibly C1s-induced vascular leakage in guinea pig skin. Vascular leakage was compared with esterolysis of N-Z-L-Tyr-Np and catalysis of EAC42 formation by C1s. Vascular leakage correlated significantly better with esterolytic activity than with EAC42 formation. The presence of a sulfonyl fluoride moiety in the compounds is important in the inhibition of C1s-induced vascular leakage.

Studies on the Molecular Basis for C1̄s Action and Comparison of C1̄s with Other Tryptic Proteases

One of the principal problems in current complement research is our understanding of the molecular basis of complement action. In order to probe the molecular biology and specificity of the serine protease, C1̄s, it was compared with three human proteases. The proteases examined were the serum enzymes C71̄s, thrombin and plasmin, and the pancreatic enzyme trypsin. An assay procedure using the simple synthetic chromophoric esters N-carbobenzoxy-l-tyrosine-p-nitrophenyl ester and N-carbobenzoxy-l-lysine-p-nitrophenyl ester as substrates was developed. A group of over 20 mono- and di-substituted benzamidines, known as competitive inhibitors of bovine tryptic enzymes, were used to probe the active sites.

The inhibition constants obtained were correlated with factors describing the lipophilicity and electronic character of the inhibitors using multiparameter regression analysis. Marked similarities were noted between C1̄s and the other enzymes. The difference between the enzymes with respect to their inhibition profiles can be interpreted on a molecular basis to account for some of the specificity shown by these enzymes.

Inhibition of guinea-pig complement by derivatives of benzamidine. I. Effect of p-nitrophenylureido derivative of m-(m-phenoxypropoxy)benzamidine on guinea-pig complement component haemolytic activity

Derivatives of benzamidine have been shown to be potent inhibitors of whole guinea-pig complement. Among these compounds the m-[m-(p-nitrophenylureido) phenoxypropoxy] benzamidine (NPUPPB) was the most potent complement inhibitor synthesized. NPUPPB blocked the addition of C1 to EAC4. It had no effect on the stability of EAC4 or the decay rate of EAC42. It also blocked the addition of C2 to EAC14. No effect of the inhibitor was found when C3 was added to EAC142. A profound inhibition occurred when either C[unk]567 was added to EAC1423 or when C5 was added to EAC1423. A slight though possibly insignificant effect occurred when C6 or C7 were added to EAC4235 and EAC42356. No effect occurred when C8 and C9 were added to the heat-stable intermediate EAC43567.

NPUPPB is a potent though poorly soluble competitive inhibitor of complement activity.