Living with Chronic Kidney Disease and Type 2 Diabetes Mellitus: The Patient and Clinician Perspective

Comorbid type 2 diabetes mellitus (T2D) and chronic kidney disease (CKD) is associated with poor health outcomes and a high economic burden. Management of these conditions remains a significant challenge for current healthcare systems. The objective of this article is to describe the experiences of patients living with T2D and CKD and their thoughts on how communication between patients and their clinicians could be improved despite the multiple comorbidities that need to be addressed. We present the individual perspectives of three patient authors, followed by relevant discussion around the management of CKD in patients with T2D by clinician authors.Audio abstract available for this article. Audio Abstract. In this audio introduction, the authors Patrick Gee (a patient author) and Eugene Wright (a clinician author) provide a brief overview and discuss the key findings of their article titled "Living with Chronic Kidney Disease and Type 2 Diabetes Mellitus: The Patient and Clinician Perspective".

Moving from Evidence to Implementation of Breakthrough Therapies for Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the most frequent cause of kidney failure, accounting for half of all cases worldwide. Moreover, deaths from DKD increased 106% between 1990 and 2013 with most attributed to cardiovascular disease. Recommended screening and monitoring for DKD is conducted in less than half of patients with diabetes. Standard-of-care treatment with an angiotensin converting enzyme inhibitor or an angiotensin receptor blocker is correspondingly low. Sodium-glucose cotransporter 2 inhibitors, glucagon-like peptide-1 receptor agonists, and a non-steroidal mineralocorticoid antagonist are highly effective therapies to reduce kidney and cardiovascular risks in DKD. However, fewer than 20% of eligible patients are receiving these agents. Critical barriers are high out-of-pocket drug costs and low reimbursement rates. Data demonstrating clinical and cost effectiveness of DKD care are needed to garner payer and healthcare system support. The pharmaceutical industry should collaborate on value-based care by increasing access through affordable drug prices. Additionally, multidisciplinary models and communication technologies tailored to individual healthcare systems are needed to support optimal DKD care. Community outreach efforts are also central to make care accessible and equitable. Finally, it is imperative that patient preferences and priorities shape implementation strategies. Access to care and implementation of breakthrough therapies for DKD can save millions of lives by preventing kidney failure, cardiovascular events, and premature death. Coalitions comprised of patients, families and community groups, healthcare professionals, healthcare systems, federal agencies and payers are essential to develop collaborative models that successfully address this major public health challenge.

SGLT-2 inhibitors or GLP-1 receptor agonists for adults with type 2 diabetes: a clinical practice guideline

CLINICAL QUESTION

What are the benefits and harms of sodium-glucose cotransporter 2 (SGLT-2) inhibitors and glucagon-like peptide 1 (GLP-1) receptor agonists when added to usual care (lifestyle interventions and/or other diabetes drugs) in adults with type 2 diabetes at different risk for cardiovascular and kidney outcomes?

CURRENT PRACTICE

Clinical decisions about treatment of type 2 diabetes have been led by glycaemic control for decades. SGLT-2 inhibitors and GLP-1 receptor agonists are traditionally used in people with elevated glucose level after metformin treatment. This has changed through trials demonstrating atherosclerotic cardiovascular disease (CVD) and chronic kidney disease (CKD) benefits independent of medications' glucose-lowering potential.

RECOMMENDATIONS

The guideline panel issued risk-stratified recommendations concerning the use of SGLT-2 inhibitors or GLP-1 receptor agonists in adults with type 2 diabetes• Three or fewer cardiovascular risk factors without established CVD or CKD: Weak recommendation against starting SGLT-2 inhibitors or GLP-1 receptor agonists.• More than three cardiovascular risk factors without established CVD or CKD: Weak recommendation for starting SGLT-2 inhibitors and weak against starting GLP-1 receptor agonists.• Established CVD or CKD: Weak recommendation for starting SGLT-2 inhibitors and GLP-1 receptor agonists.• Established CVD and CKD: Strong recommendation for starting SGLT-2 inhibitors and weak recommendation for starting GLP-1 receptor agonists.• For those committed to further reducing their risk for CVD and CKD outcomes: Weak recommendation for starting SGLT-2 inhibitors rather than GLP-1 receptor agonists.

HOW THIS GUIDELINE WAS CREATED

An international panel including patients, clinicians, and methodologists created these recommendations following standards for trustworthy guidelines and using the GRADE approach. The panel applied an individual patient perspective.

THE EVIDENCE

A linked systematic review and network meta-analysis (764 randomised trials included 421 346 participants) of benefits and harms found that SGLT-2 inhibitors and GLP-1 receptor agonists generally reduce overall death, and incidence of myocardial infarctions, and end-stage kidney disease or kidney failure (moderate to high certainty evidence). These medications exert different effects on stroke, hospitalisations for heart failure, and key adverse events in different subgroups. Absolute effects of benefit varied widely based on patients' individual risk (for example, from five fewer deaths in the lowest risk to 48 fewer deaths in the highest risk, for 1000 patients treated over five years). A prognosis review identified 14 eligible risk prediction models, one of which (RECODe) informed most baseline risk estimates in evidence summaries to underpin the risk-stratified recommendations. Concerning patients' values and preferences, the recommendations were supported by evidence from a systematic review of published literature, a patient focus group study, a practical issues summary, and a guideline panel survey.

UNDERSTANDING THE RECOMMENDATION

We stratified the recommendations by the levels of risk for CVD and CKD and systematically considered the balance of benefits, harms, other considerations, and practical issues for each risk group. The strong recommendation for SGLT-2 inhibitors in patients with CVD and CKD reflects what the panel considered to be a clear benefit. For all other adults with type 2 diabetes, the weak recommendations reflect what the panel considered to be a finer balance between benefits, harms, and burdens of treatment options. Clinicians using the guideline can identify their patient's individual risk for cardiovascular and kidney outcomes using credible risk calculators such as RECODe. Interactive evidence summaries and decision aids may support well informed treatment choices, including shared decision making.

A living WHO guideline on drugs to prevent covid-19

CLINICAL QUESTION

What is the role of drugs in preventing covid-19? WHY DOES THIS MATTER?: There is widespread interest in whether drug interventions can be used for the prevention of covid-19, but there is uncertainty about which drugs, if any, are effective. The first version of this living guideline focuses on the evidence for hydroxychloroquine. Subsequent updates will cover other drugs being investigated for their role in the prevention of covid-19.

RECOMMENDATION

The guideline development panel made a strong recommendation against the use of hydroxychloroquine for individuals who do not have covid-19 (high certainty).

HOW THIS GUIDELINE WAS CREATED

This living guideline is from the World Health Organization (WHO) and provides up to date covid-19 guidance to inform policy and practice worldwide. Magic Evidence Ecosystem Foundation (MAGIC) provided methodological support. A living systematic review with network analysis informed the recommendations. An international guideline development panel of content experts, clinicians, patients, an ethicist and methodologists produced recommendations following standards for trustworthy guideline development using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

UNDERSTANDING THE NEW RECOMMENDATION

The linked systematic review and network meta-analysis (6 trials and 6059 participants) found that hydroxychloroquine had a small or no effect on mortality and admission to hospital (high certainty evidence). There was a small or no effect on laboratory confirmed SARS-CoV-2 infection (moderate certainty evidence) but probably increased adverse events leading to discontinuation (moderate certainty evidence). The panel judged that almost all people would not consider this drug worthwhile. In addition, the panel decided that contextual factors such as resources, feasibility, acceptability, and equity for countries and healthcare systems were unlikely to alter the recommendation. The panel considers that this drug is no longer a research priority and that resources should rather be oriented to evaluate other more promising drugs to prevent covid-19.

UPDATES

This is a living guideline. New recommendations will be published in this article and signposted by update notices to this guideline.

READERS NOTE

This is the first version of the living guideline for drugs to prevent covid-19. It complements the WHO living guideline on drugs to treat covid-19. When citing this article, please consider adding the update number and date of access for clarity.

A living WHO guideline on drugs for covid-19

Updates

This is the fourteenth version (thirteenth update) of the living guideline, replacing earlier versions (available as data supplements). New recommendations will be published as updates to this guideline.

Clinical question

What is the role of drugs in the treatment of patients with covid-19?

Context

The evidence base for therapeutics for covid-19 is evolving with numerous randomised controlled trials (RCTs) recently completed and underway. Emerging SARS-CoV-2 variants and subvariants are changing the role of therapeutics.

What is new?

The guideline development group (GDG) defined 1.5% as a new threshold for an important reduction in risk of hospitalisation in patients with non-severe covid-19. Combined with updated baseline risk estimates, this resulted in stratification into patients at low, moderate, and high risk for hospitalisation. New recommendations were added for moderate risk of hospitalisation for nirmatrelvir/ritonavir, and for moderate and low risk of hospitalisation for molnupiravir and remdesivir. New pharmacokinetic evidence was included for nirmatrelvir/ritonavir and molnupiravir, supporting existing recommendations for patients at high risk of hospitalisation. The recommendation for ivermectin in patients with non-severe illness was updated in light of additional trial evidence which reduced the high degree of uncertainty informing previous guidance. A new recommendation was made against the antiviral agent VV116 for patients with non-severe and with severe or critical illness outside of randomised clinical trials based on one RCT comparing the drug with nirmatrelvir/ritonavir. The structure of the guideline publication has also been changed; recommendations are now ordered by severity of covid-19.

About this guideline

This living guideline from the World Health Organization (WHO) incorporates new evidence to dynamically update recommendations for covid-19 therapeutics. The GDG typically evaluates a therapy when the WHO judges sufficient evidence is available to make a recommendation. While the GDG takes an individual patient perspective in making recommendations, it also considers resource implications, acceptability, feasibility, equity, and human rights. This guideline was developed according to standards and methods for trustworthy guidelines, making use of an innovative process to achieve efficiency in dynamic updating of recommendations. The methods are aligned with the WHO Handbook for Guideline Development and according to a pre-approved protocol (planning proposal) by the Guideline Review Committee (GRC). A box at the end of the article outlines key methodological aspects of the guideline process. MAGIC Evidence Ecosystem Foundation provides methodological support, including the coordination of living systematic reviews with network meta-analyses to inform the recommendations. The full version of the guideline is available online in MAGICapp and in PDF on the WHO website, with a summary version here in The BMJ. These formats should facilitate adaptation, which is strongly encouraged by WHO to contextualise recommendations in a healthcare system to maximise impact.

Future recommendations

Recommendations on anticoagulation are planned for the next update to this guideline. Updated data regarding systemic corticosteroids, azithromycin, favipiravir and umefenovir for non-severe illness, and convalescent plasma and statin therapy for severe or critical illness, are planned for review in upcoming guideline iterations.

Exploring Barriers and Potential Solutions in Home Dialysis: An NKF-KDOQI Conference Outcomes Report

Home dialysis therapy, including home hemodialysis and peritoneal dialysis, is underused as a modality for the treatment of chronic kidney failure. The National Kidney Foundation-Kidney Disease Outcomes Quality Initiative sponsored a home dialysis conference in late 2017 that was designed to identify the barriers to starting and maintaining patients on home dialysis therapy. Clinical, operational, policy, and societal barriers were identified that need to be overcome to ensure that dialysis patients have the freedom to choose their treatment modality. Education of patients and patient partners, as well as health care providers, about home dialysis therapy, if offered at all, is often provided in a cursory manner. Lack of exposure to home dialysis therapies perpetuates a lack of familiarity and thus a hesitancy to refer patients to home dialysis therapies. Patient and care partner support, both psychosocial and financial, is also critical to minimize the risk for burnout leading to dropout from a home dialysis modality. Thus, the facilitation of home dialysis therapy will require a systematic change in chronic kidney disease education and the approach to dialysis therapy initiation, the creation of additional incentives for performing home dialysis, and breakthroughs to simplify the performance of home dialysis modalities. The home dialysis work group plans to develop strategies to overcome these barriers to home dialysis therapy, which will be presented at a follow-up home dialysis conference.

The sustainability of a community pharmacy intervention to improve the quality use of asthma medication

WHAT IS KNOWN AND OBJECTIVE

A previously published asthma intervention used a software application to data mine pharmacy dispensing records and generate a list of patients with potentially suboptimal management of their asthma; in particular, a high rate of provision of reliever medication. These patients were sent educational material from their community pharmacists and advised to seek a review of their asthma management from their general practitioner. The intervention resulted in a 3-fold improvement in the ratio of dispensed preventer medication (inhaled corticosteroids) to reliever medication (short-acting beta-2 agonists). This follow-up study aimed to determine the long-term effects of the intervention programme on the preventer-to-reliever (P:R) ratio.

METHODS

The same data mining software was modified so that it could re-identify patients who were originally targeted for the intervention. Community pharmacists who participated in the previous intervention installed the modified version of the software. The dispensing data were then de-identified, encrypted and transferred via the Internet to a secure server. The follow-up dispensing data for all patients were compared with their pre- and post-intervention data collected originally.

RESULTS AND DISCUSSION

Of the 1551 patients who were included in the original study, 718 (46·3%) were eligible to be included in the follow-up study. The improved P:R ratio was sustained for at least 12 months following the intervention (P < 0·01). The sustained increase in the P:R ratio was attributed to significant decreases in the average daily usage of reliever medication (P < 0·0001).

WHAT IS NEW AND CONCLUSION

The follow-up study demonstrated a sustained improvement in the ratio of dispensed preventer medication to reliever medication for asthma. The intervention has the potential to show long-lasting and widespread improvements in asthma management, improved health outcomes for patients, and ultimately, a reduced burden on the health system.

Temporal discrimination learning of operant feeding in goldfish (Carassius auratus)

Operant temporal discrimination learning was investigated in goldfish. In the first experiment, there was a fixed daily change in illumination. Eight subjects were trained to operate a lever that reinforced each press with food. The period during which responses were reinforced was then progressively reduced until it was 1 hr in every 24. The final 1-hr feeding schedule was maintained over 4 weeks. The feeding period commenced at the same time each day throughout. The food dispensers were then made inactive, and a period of extinction ensued for 6 days. The pattern of responding suggested that the fish were able to exhibit temporal discrimination in anticipation of feeding time. This pattern of responding persisted for a limited number of days during the extinction procedure. The second experiment produced evidence that operant temporal discrimination could develop under continuous illumination.

Statistical modeling and analyses of a base-specific Salmonella mutagenicity assay

Statistical features of a base-specific Salmonella mutagenicity assay are considered in detail, following up on a previous report comparing responses of base-specific Salmonella (Ames II) strains with those of traditional tester strains. In addition to using different Salmonella strains, the new procedure also differs in that it is performed as a microwell fluctuation test, as opposed to the standard plate or preincubation test. This report describes the statistical modeling of data obtained from the use of these new strains in the microwell test procedure. We emphasize how to assess any significant interactions between replicate cultures and exposure doses, and how to identify a significant increase in the mutagenic response to a series of concentrations of a test substance.

Transcriptional activity of quinone methides derived from the tumor promoter butylated hydroxytoluene in HepG2 cells

Butylated hydroxytoluene (BHT) is a pulmonary toxin and tumor promoter in mice presumably due to the formation of two quinone methides (QMs) that alkylate cellular nucleophiles. The activation of stress genes by these electrophilic metabolites was investigated with an assay system consisting of 14 recombinant cell lines derived from the human hepatoma line HepG2, each carrying a unique promoter or response element construct fused to the reporter gene for chloramphenicol acetyl transferase (CAT). The largest responses to QMs occurred in cells containing either the metallothionein IIA, glutathione S-transferase Ya, or 70 kDa heat shock protein promoter, or the xenobiotic response element. The other cell lines exhibited only small or no effects. These results are consistent with transcriptional activities reported for several other electrophiles known to undergo covalent interactions with proteins.

Paediatric exploratory ingestions of paracetamol

AIM

To review paediatric exploratory ingestions of paracetamol presenting to Christchurch Hospital Emergency Department.

METHOD

A retrospective review of all paediatric patients presenting with paracetamol ingestion over a 12 month period.

RESULTS

During the study period there were 88 paediatric presentations for possible toxic ingestions involving paracetamol and 85 of these were exploratory self-ingestion. The male to female ratio was 43:42 and the mean age was 35 months. Paracetamol suspension was ingested in 79/85 cases and tablets in 6/85. The mean four hour plasma level was 162 mumol/L and all levels were well below the possible toxic level (1300 mumol/L). There was very poor correlation between estimated dose ingested and plasma level.

CONCLUSION

Toxicity from paediatric exploratory ingestion of paracetamol is extremely rare. To reduce the potential for poisoning, bottles and prescriptions of paracetamol should have less than a total dose of 4 g. The authors recommend that unwitnessed exploratory ingestions of paracetamol in children require no treatment if the estimated maximum ingested dose is below 140 mg/kg. Above this dose, treatment is based on the result of a plasma paracetamol level drawn four hours after ingestion. Gastrointestinal decontamination should be reserved for the rare occasions of a definite witnessed ingestion of a dose exceeding 140 mg/kg.

Comparison of responses of base-specific Salmonella tester strains with the traditional strains for identifying mutagens: the results of a validation study

The ability of a TA7000 series of Salmonella his- mutant tester strains to detect mutagens as classified by the traditional tester strains (TA100, TA98, TA1535, TA1537, TA97, TA102 and TA104) was evaluated using 30 coded chemicals, 5 of which were duplicates with different code numbers. The TA7000 series of tester strains were TA7001, TA7002, TA7003, TA7004, TA7005 and TA7006, each of which reverts by a specific base substitution. In addition, each chemical was tested in a mixture of the base-specific strains (the Mix), plus the traditional strains, TA98 and TA1537. A liquid version of the Salmonella mutagenicity assay was performed in microtiter plates to allow partial automation for increased throughput. The results were compared to those in the National Toxicology Program (NTP) database, which were obtained from the traditional strains in the preincubation assay. In the two strains common to both protocols, TA98 and TA1537, the agreement was 80% and 85%, respectively. When compared to the NTP results for TA100, the Mix gave a 72% concordance, while the addition of the frameshift tester strain, TA98, increased the agreement to 76%. The overall agreement on positive or negative classifications of mutagenicity was 88% for the 25 chemicals tested. There were three notable exceptions to the overall agreement. Benzaldehyde was detected as a mutagen in TA7005 in contrast to its classification as a non-mutagen in the NTP database. This does not necessarily contradict the NTP results because the base-specific strains may respond to different mutagens. Two weak mutagens in the NTP database, 1-chloro-2-propanol and isobutyl nitrite, were not detected as mutagens in the base-specific new strains in the liquid protocol. While there are a number of major differences in the two assays, it was concluded that the results from each procedure are comparable.

Nutritional assessment in elderly care--a team approach

This work began in February 1996 when nationally questions were being asked about the nutritional care patients were receiving in hospital. Within the Elderly Care Unit the multi-disciplinary team was also questioning the nutritional care patients received. The main concern raised was the lack of consistent nutritional assessment occurring within the unit. A multi-disciplinary nutritional group was formed to address this area of concern. It developed an assessment tool that identifies those patients at risk and provides guidelines for appropriate action.

Identification of functional conserved residues of CTP:glycerol-3-phosphate cytidylyltransferase. Role of histidines in the conserved HXGH in catalysis

The CTP:glycerol-3-phosphate cytidylyltransferase (GCT) of Bacillus subtilis has been shown to be similar in primary structure to the CTP:phosphocholine cytidylyltransferases of several organisms. To identify the residues of this cytidylyltransferase family that function in catalysis, the conserved hydrophilic amino acid residues plus a conserved tryptophan of the GCT were mutated to alanine. The most dramatic losses in activity occurred with H14A and H17A; these histidine residues are part of an HXGH sequence similar to that found in class I aminoacyl-tRNA synthetases. The kcat values for H14A and H17A were decreased by factors of 5 x 10(-5) and 4 x 10(-4), respectively, with no significant change in Km values. Asp-11, which is found near the HXGH sequence in the cytidylyltransferases but not aminoacyl-tRNA synthetases, was also important for activity, with the D11A mutation decreasing activity by a factor of 2 x 10(-3). Several residues found in the sequence RTEGISTT, a signature sequence for this cytidylyltransferase family, as well as other isolated residues were also shown to be important for activity, with kcat values decreasing by factors of 0.14-4 x 10(-4). The Km values of three mutant enzymes, D38A, W74A, and D94A, for both CTP and glycerol-3-phosphate were 6-130-fold higher than that of the wild-type enzyme. Mutant enzymes were analyzed by two-dimensional NMR to determine if the overall structures of the enzymes were intact. One of the mutant enzymes, D66A, was defective in overall structure, but several of the others, including H14A and H17A, were not. These results indicate that His-14 and His-17 play a role in catalysis and suggest that their role is similar to the role of the His residues in the HXGH sequence in class I aminoacyl-tRNA synthetases, i.e. to stabilize a pentacoordinate transition state.

Detection of peroxisome proliferators using a reporter construct derived from the rat acyl-CoA oxidase promoter in the rat liver cell line H-4-II-E

Peroxisome proliferators are nongenotoxic carcinogens capable of causing rapid transcriptional activation of genes comprising the rodent beta-oxidation pathway. Numerous compounds, such as hypolipidemic drugs, herbicides, plasticizers, and analgesics have been identified as peroxisome proliferators in rodents. We have developed a whole-cell in vitro assay to detect peroxisome proliferators in approximately 48 h. A promoter::chloramphenicol acetyltransferase (CAT) fusion construct for rat acyl-CoA oxidase (ACOX), the rate-limiting enzyme in the peroxisomal beta-oxidation pathway, was stably transfected into the rat liver cell line H-4-II-E. Treatment of the recombinant cell line (ACOX::CAT) with peroxisome proliferators, WY 14,643, clofibrate, di(2-ethylhexyl) phtalhate, and acetylsalicylic acid resulted in differential increases of CAT protein 48 h after exposure. Nonsteroidal anti-inflammatory drugs including ibuprofen, fenbupen, naproxen, and acetaminophen also up-regulated ACOX::CAT. Phorbol 12-myristate 13-acetate, a nongenotoxic carcinogen that is not classified as a peroxisome proliferator, also resulted in a slight induction of ACOX::CAT, consistent with the role of cell proliferation in tumor progression. The carcinogenic compounds 4-nitroquinoline N-oxide, ethyl methanesulfonate, diethylstilbestrol, and 2-aminoanthracene did not induce ACOX::CAT. Although the significance of peroxisome proliferators and their impact on humans is still unknown, the ability to identify them is of interest to the pharmaceutical and chemical industries. This assay was able to detect known peroxisome proliferators tested in approximately 48 h of exposure and to distinguish them from genotoxic carcinogens.

Stress responses to DNA damaging agents in the human colon carcinoma cell line, RKO

DNA damage results from a wide variety of external agents such as chemicals and radiation. The consequences of exposure to agents that damage DNA have been traditionally studied from the perspective of cell survival and mutagenesis. Mutations are late endpoints of DNA damage. Cells respond to the earlier stages of DNA damage by inducing the expression of several genes, including those specific of the nature of the lesion. These early transcriptional responses are likely to predetermine the later fate of the damaged cell. Genes activated during this early response include those involved in DNA repair, replication, and growth control. We are interested in the transcriptional mechanisms by which cells respond to DNA damaging agents. To facilitate the measurement of gene induction, we used seven different reporter constructs integrated stably into the RKO cell line derived from a human colon carcinoma. These constructs were derived from promoters and/or response elements isolated from genes associated with DNA damage responses in human cells, and were fused to the bacterial reporter gene, choramphenicol acetyl transferase (CAT). The cell lines generated in this manner contain the promoters and/or response elements representing DNA polymerase beta, p53, gadd (growth arrest and DNA damage) 45 and 153, c-fos, TPA response element, and tissue-type plasminogen activator. These recombinant cell lines were assembled in a 96-well microtiter plate permitting their simultaneous exposure to compounds and subsequent CAT protein measurement. This assembly has been designated the CAT-Tox (D) assay. These cell lines were exposed to different classes of DNA damaging agents including those which covalently join bases to form dimers (e.g., UVC irradiation), generate DNA adducts by alkylation (e.g., methylmethane sulfonate [MMS], ethylmethane sulfonate [EMS], N-methyl-N-nitro-N-nitrosoguanine [MNNG], dimethylnitrosamine [DMN]), cross-link DNA (e.g., mitomycin C), and inhibit DNA replication by intercalative (e.g., actinomycin D) and nonintercalative (e.g., hydroxyurea) mechanisms. The transcriptional responses were measured as a function of the accumulation of CAT protein using antibodies against CAT protein in a standard ELISA. Endogenous cellular responses were evaluated for a number of the genes represented in the assay at both the mRNA and protein levels by Northern and Western blot analysis, respectively. These data corroborate the stress-induced responses measured by CAT ELISA in the CAT-Tox (D) assay, demonstrating the usefulness of this assay as a rapid and sensitive method for detection of DNA damaging agents in human cells.

The CAT-Tox (L) assay: a sensitive and specific measure of stress-induced transcription in transformed human liver cells

Identifying and measuring the molecular mechanisms of toxicity is an important goal in hazard assessment. We have developed an assay in transformed human liver cells to simultaneously measure the transcriptional responses of 14 stress promoter- or response element-chloramphenicol acetyl transferase (CAT) fusion constructs that are stably integrated into the HepG2 cell line. This assay can measure a wide spectrum of stresses, both toxic and nontoxic, such as protein and protein biosynthesis perturbations, DNA damage, heavy metals, and planar aromatic hydrocarbons. We found that each promoter or response element can be induced by one or more of four chemicals that were tested in the assay. These results have been interpreted in light of the current models of action for each compound. The responses of this assay system can distinguish among compounds that are closely related in their structure and have been shown previously to elicit similar biological activities in simple assay systems. We have designated this technique the CAT-Tox (L)iver assay. It measures a broad range of cellular stresses and toxicants at levels that were comparable to or below those of established methods. The induction profiles generated using the CAT-Tox (L) assay can help to elucidate the molecular mechanisms by which chemicals exert their actions on human cells. These profiles can be indicative of both toxic and nontoxic processes that are occurring in the cell. We propose that this cellular stress assay can serve as a screen for a variety of substances at the molecular level.

Aquatic surface respiration, buoyancy control and the evolution of air-breathing in gobies (Gobiidae: Pisces)

The role of a buccal gas bubble, held while performing aquatic surface respiration (ASR; ventilating the gills with surface water during hypoxia), was examined in benthic, intertidal Australian gobies (Favonigobius tamarensis, F. exquisitus, Pseudogobius olorum, Chlamydogobius sp., Mugilogobius paludis, Cryptocentroides cristatus and Arenigobius bifrenatus). Analyses of the forces of lift and weight of the head and body during ASR indicate a hydrostatic role for the bubble. During ASR, lift from the bubble was sufficient to provide neutral or positive buoyancy to the head, anchoring the mouth at the water surface. A buoyancy role was confirmed by experiments demonstrating the ability of some species to alter bubble volume, to compensate either for different body positions or for water densities (salinities). Use of the bubble for aerial respiration by Cryptocentroides, Mugilogobius, Chlamydogobius and Arenigobius was confirmed in hypoxia by the presence of blood-filled capillaries in the buccal subepithelium (mean air&shy;blood barrier less than 30 &micro;m) in areas of the buccal cavity that contacted the bubble. Blood-filled capillaries were rare or absent in normoxia in all species except Mugilogobius. Cutaneous respiration was inferred from the presence of blood-filled capillaries in the dermis and epidermis of emersed portions of the head in Mugilogobius, Chlamydogobius and Arenigobius. The buccal bubble has respiratory and hydrostatic roles and there is support for the hypothesis that ASR and the buoyancy regulation (air-gulping) required to perform it effectively are prerequisite steps in the evolution of air-breathing in these gobies.

Detection and classification of mutagens: a set of base-specific Salmonella tester strains

A detection and classification system for mutagens has been developed that identifies the six possible base-pair substitution mutations. A set of six Salmonella typhimurium (TA7001 to TA7006) strains has been constructed, each of which carries a unique missense mutation in the histidine biosynthetic operon. In addition to the his mutation, these strains carry different auxiliary features that enhance the mutability of the target his mutation. These include the R factor pKM101, which has the SOS-inducible mucAB system; a deletion of the uvrB component of excision repair; and rfa mutations to increase the accessibility of bulky chemicals to the bacteria. Another set of strains (TA7041 to TA7046) contain a wild-type rfa gene. Reversion via the base substitution unique to each strain was verified by sequence analyses of > 800 revertants obtained from different types of mutagens. The strains have considerably lower spontaneous reversion frequencies and detect a variety of mutagens at a sensitivity comparable to the Salmonella tester strains TA100, TA102, and TA104. The low spontaneous frequency of reversion of a mixture of the six tester strains (approximately 10 revertants per plate) enables a single mutation assay with the mixture that is followed by classification of the type of mutation with the individual strains.

Vasoinhibitory activity of synthetic peptides from the amino terminus of chromogranin A

Naturally occurring amino terminal fragments of chromogranin A (CGA), the calcium-binding protein found in all endocrine secretory vesicles, have vasoinhibitory activity when tested in isolated segments of the endothelium-denuded human saphenous vein. Synthetic peptides corresponding to sequences within the first 76 residues of chromogranin A have been made and tested for biological activity. Full length vasostatin I (CGA1-76) (40 nM), but not the truncated vasostatin I, CGA1-40 (100 nM) mimics natural chromogranin A fragments in its inhibition of contractions induced by endothelin-1 (ET-1) in calcium containing medium. CGA1-40 (100 nM) mimics the inhibitory effect of the vasostatins on the contractions induced in the absence of extracellular calcium by high potassium and noradrenaline, but not by ET-1. The iodinated peptides both exhibit saturable binding in an aortic smooth muscle cell line, indicative of a single class of high affinity binding protein ('receptor' with an apparent KD of approximately 45 nM. This binding is not affected by endothelin-1. Iodinated peptides can be crosslinked to a single polypeptide in binding experiments performed on intact calf aortic smooth muscle cells.

Adaptive mutation by deletions in small mononucleotide repeats

Adaptive reversion of a +1 frameshift mutation in Escherichia coli, which requires homologous recombination functions, is shown here to occur by -1 deletions in regions of small mononucleotide repeats. This pattern makes improbable recombinational mechanisms for adaptive mutation in which blocks of sequences are transferred into the mutating gene, and it supports mechanisms that use DNA polymerase errors. The pattern appears similar to that of mutations found in yeast cells and in hereditary colon cancer cells that are deficient in mismatch repair. These results suggest a recombinational mechanism for adaptive mutation that functions through polymerase errors that persist as a result of a deficiency in post-synthesis mismatch repair.

Inhibition of parathyroid hormone secretion by amino-terminal chromogranin peptides

The parathyroid gland responds to decreases in levels of extracellular calcium by increasing the secretion of both PTH and chromogranin-A (CGA) in approximately equal molar ratios. Because CGA has been suggested to be a precursor for biologically active peptides, we used primary cultures of bovine parathyroid cells to examine the effects of various peptides from CGA as well as analogous peptides from chromogranin-B (CGB) on PTH secretion. In concentrations from 10(-8)-10(-7) M, amino-terminal peptide CGA-(1-76) effectively inhibited the release of PTH in response to low extracellular calcium. Truncated analogs of this peptide, CGA-(1-40), CGB-(1-41), and CGA-(17-38) were also found to be active in the following order: CGA-(1-76) = CGA-(1-40) = CGB-(1-41) > CGA-(17-38). The biological activity of CGA-(1-40) was markedly reduced after reduction and alkylation, which resulted in disruption of the single disulfide bond between Cys17 and Cys38. Moreover, peptides derived from other regions of CGA and CGB, which included CGA-(403-428), CGB-(1-16), CGB-(316-326), and CGB-(635-657) were inactive. Pulse-chase experiments, using primary cultures of bovine parathyroid cells, revealed the presence of a CGA peptide in the culture medium that had the same amino-terminal sequence and mobility on sodium dodecyl sulfate-polyacrylamide gels as synthetic CGA-(1-76). Furthermore, in binding and cross-linking studies using intact parathyroid cells, CGA-(1-40) formed a single, covalently linked protein complex with a mol wt of 78,000. Formation of the protein complex could be completely inhibited in the presence of an excess of either CGB-(1-41) or CGA-(17-38). These results show that a naturally occurring amino-terminal peptide from CGA as well as shorter analogs can act as potent inhibitors of PTH secretion, and that their biological activity may be mediated through binding to a specific cell surface protein.

Expression of neuropeptide processing enzymes and neurosecretory proteins in ependyma and choroid plexus epithelium

Recent studies suggest that brain ependyma and choroid plexus produce neuropeptide processing enzymes. To facilitate the understanding of these cells and their ability to produce biologically active peptides, we developed cultures of defined cell type. Ependymal cells were characterized by morphological criteria, and choroid plexus epithelial cell lines were characterized by the presence of the mRNA for IGF-II and transthyretin, a thyroxine binding protein produced in liver and choroid plexus. The ependymal cells and the choroid plexus epithelial cell lines were then examined for the presence of mRNAs for various neuropeptide processing enzymes. Northern blot analysis revealed high levels of furin, carboxypeptidase E, and peptidyl glycine alpha-amidating monooxygenase mRNAs, with levels in ependymal cells comparable to those in brain or pituitary. Carboxypeptidase E activity was detected in medium from cultured ependymal cells; this activity was identified as carboxypeptidase E based on the acidic pH optimum and sensitivity to various inhibitors. The mRNAs for other neuropeptide processing enzymes, such as prohormone convertases 1 and 2, were not detected on Northern blots of RNA from ependyma or choroid plexus epithelium. Since ependyma and choroid plexus epithelium express a subset of processing enzymes, we suggest that these cells have the capacity to produce biologically active peptides. Initial screening by reverse transcriptase-polymerase chain reaction assays has demonstrated the presence of mRNA for the neurosecretory proteins chromogranin B and secretogranin II in both ependyma and choroid plexus epithelium.

Effects of calcium on recombinant bovine chromogranin A

Bovine chromogranin A, the acidic calcium-binding protein characteristic of endocrine secretory vesicles, has been expressed in Escherichia coli using the pET3a vector system under T7 polymerase control. The expressed protein is located in the bacterial cytosol and can be purified from bacterial proteins by a heat treatment step, followed by gel filtration, anion-exchange, and reversed-phase chromatography. The purified recombinant chromogranin A has an apparent M(r) of ca. 72,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, in spite of its 432-amino acid polypeptide chain, consistent with observations on natural chromogranin A. The primary structure has been confirmed by mass spectral analysis of tryptic peptides, by Edman degradation of the intact protein, and by immunoreactivity with sequence-specific antibodies. Analysis by circular dichroism spectroscopy shows pH- and concentration-dependent spectra. The spectra are Ca2(+)-dependent from 5 to 40 microM.

Genomic heterogeneity of DNA repair. Role in aging?

The introduction and repair of DNA lesions are generally heterogeneous with respect to different genomic domains. In particular, the repair of helix-distorting damage, such as the cyclobutane pyrimidine dimers (CPD) induced by ultraviolet light occurs selectively in expressed genes. This is due in large part to the preferential repair of transcribed DNA strands, which is then reflected in a bias toward mutagenesis from persisting lesions in nontranscribed strands. Consequently, determination of overall genomic repair efficiencies may not be a good indicator of cellular sensitivity to agents that damage DNA. Although some studies suggest an age-related accumulation of altered nucleotides in DNA, we do not know the intragenomic distribution of those changes and whether they are relevant to the physiological aspects of aging. Subtle changes in the pattern of preferential repair during maturation could have profound effects on cell and tissue function. DNA repair has been analyzed in differentiating cell systems as possible models for aging. We have observed attenuated overall repair of CPD in differentiated rat myoblasts or PC12 neuron-like cells. In both model systems, several expressed genes have been shown to be repaired relatively efficiently but without strand specificity. In another model system of human HT1080 fibroblasts differentiating in the presence of dexamethasone, we demonstrated enhanced repair in the gene for plasminogen activator inhibitor I whose transcription is induced and, correspondingly, a reduced repair rate in the urokinase plasminogen activator gene whose transcription is suppressed. We conclude that any attempted correlation of the phenomena of aging with DNA repair should focus on the relevant genes in the tissue of interest.

Differential subcellular distribution of PC1, PC2 and furin in bovine adrenal medulla and secretion of PC1 and PC2 from this tissue

The subcellular distribution of PC1, PC2 and furin was determined in bovine adrenal medulla by immunoblotting of fractions obtained by density gradient centrifugation. PC1 and PC2 were found to be confined to chromaffin granules whereas furin (C-terminal-peptide) was absent from these organelles. Stimulation of bovine adrenal medulla by carbamoylcholine chloride induced the secretion of PC1 and PC2. The secreted enzymes had the same molecular size as PC1 and PC2 present in chromaffin granules.

Immunological characterization of the endoproteases PC1 and PC2 in adrenal chromaffin granules and in the pituitary gland

Specific antisera against synthetic fragment of the endoproteases, PC1 and PC2, were used to characterize these proteins. In one-dimensional immunoblots these antisera labelled components of 85 kDa for PC1 and of 70 kDa for PC2 in purified bovine chromaffin granules and anterior and posterior pituitary of ox and rat. In membranes of bovine chromaffin granules glycoprotein H was identified as the major PC2 immunoreactive spot. A major part of these endoproteases appeared membrane bound.

Clastogenic and mutagenic actions of active species generated in the 6-hydroxydopamine/oxygen reaction: effects of scavengers of active oxygen, iron, and metal chelating agents

A pro-oxidant triphenol, 6-hydroxydopamine (6-OHDA), induced mutations in the Salmonella typhimurium TA 104 tester strain (over the concentration range to 800 microM), and induced chromosomal aberrations in cultured Chinese hamster ovary (CHO) cells at lower concentrations (up to 90 microM). It was however only marginally mutagenic (up to cytotoxic levels of 200 microM) in the TA102 tester strain. Clastogenicity in the more sensitive CHO cell assay was mediated by activated oxygen. Superoxide dismutase decreased the incidence of chromosomal aberrations by 60% and catalase (or superoxide dismutase plus catalase) decreased the incidence to control levels. The clastogenicity of 6-OHDA was dependent upon unsequestered transition metal ions, since addition of EDTA plus desferrioxamine decreased chromosomal aberrations by 90%. The simplest explanation of the data is that genotoxicity is mediated by active species generated in a Fenton-type reaction between 6-OHDA and H2O2 catalyzed by traces of metals in the medium.

Intermediates in the aerobic autoxidation of 6-hydroxydopamine: relative importance under different reaction conditions

Autoxidation of 6-hydroxydopamine (6-OHDA) proceeds through a balanced network of: transition metal ions, superoxide, hydrogen peroxide, hydroxyl radicals, and other species. The contribution of each to the reaction mechanism varies dramatically depending upon which scavengers are present. The contribution of each propagating intermediate increases when the involvement of others is diminished. Thus, superoxide (which is relatively unimportant when metal ions can participate) dominates the reaction when transition metal ions are bound (especially at higher pH), and it becomes essential in the simultaneous presence of catalase plus chelators. Transition metal ions participate more if superoxide is excluded; hydrogen peroxide becomes more important if both .O2- and metal ions are excluded; and hydroxyl radicals contribute more to the reaction mechanism if both H2O2 and .O2- are excluded. Superoxide dismutase inhibited strongly, by two distinct mechanisms: a high affinity mechanism (less than 13% inhibition) at catalytically effective concentrations, and a low affinity mechanism (almost complete inhibition at the highest concentrations) which depends upon both metal binding and catalytic actions. In the presence of DETAPAC catalytic concentrations of superoxide dismutase inhibited by over 98%. Conversely, metal chelating agents inhibited strongly in the presence of superoxide dismutase. When present alone they stimulated (like EDTA), inhibited (like desferrioxamine), or had little effect (like DETAPAC). Catalase which stimulated slightly but consistently (less than 5%) when added alone, inhibited 100% in the presence of superoxide dismutase + DETAPAC. However, in the absence of DETAPAC, catalase decreased inhibition by superoxide dismutase, yielding a 100% increase in reaction rate. Hydroxyl scavengers (formate, mannitol or glucose) alone produced little or no (less than 10%) inhibition, but inhibited by 30% in the presence of catalase + superoxide dismutase. Paradoxically, they stimulated the reaction in the presence of catalase + superoxide dismutase + DETAPAC.

Redox state of cytochrome c in the presence of the 6-hydroxydopamine/oxygen couple: oscillations dependent on the presence of hydrogen peroxide or superoxide

The reduction of ferricytochrome c in the presence of 6-hydroxydopamine/O2 mixtures was examined under various reaction conditions. As the autoxidation of 6-hydroxydopamine progressed to completion, there were fluctuations in the net redox reactivity between reducing and oxidizing steady states. This was reflected in a sequence of damped oscillations in the redox state of cytochrome c. Corresponding to the time when 6-hydroxydopamine was 75-100% exhausted, reoxidation of the ferrocytochrome c occurred (prevented by catalase or catalase plus superoxide dismutase). After the H2O2, in turn, was mostly consumed, the next phase commenced in which the cytochrome c became reduced for a second time. This reductive phase was 52% inhibited by superoxide dismutase. In the subsequent and final phase of the process, a progressive oxidation of cytochrome c lasting at least 24 h was observed. Of the initial reduction of ferricytochrome c, at most 37% can be attributed to direct reduction by 6-hydroxydopamine or its semiquinone. This initial net reduction of cytochrome c was inhibited 51% by superoxide dismutase and 41% by catalase. However, since either catalase or superoxide dismutase inhibited the autoxidation of 6-hydroxydopamine by at least as much as it slowed the reduction of cytochrome c, their effects in slowing the reduction of cytochrome c resulted largely from the decreased production of those free radicals which reduce ferricytochrome c, and only in part from accelerated removal. Elimination of the actions of transition metal ions (whether by passage of the buffer solutions through Chelex 100 resins or by addition of desferrioxamine to the reaction medium) slowed both the reoxidation and rereduction by up to 96%. Addition of mannitol decreased the rate of the first reoxidation by 25% and increased the rate of the rereduction by 7%. In general, the oscillations are explicable in terms of changes in the steady state levels of O-2 and H2O2, with metal ions playing a major role and hydroxyl radicals a minor role in both the reoxidation and rereduction.

6-hydroxydopamine does not reduce molecular oxygen directly, but requires a coreductant

The autoxidation of 6-hydroxydopamine (6HODA) was virtually blocked (k2 less than 10(-15) M-1 S-1 at pH 8.0, ionic strength 0.04) by the simultaneous presence of diethylenetriaminepentaacetic acid (DTPA), catalase, and superoxide dismutase (SOD). No quinone product or oxygen consumption was detectable after 12 min under these conditions. Thus, if 6HODA is to react with molecular oxygen at a measurable rate, some other redox species is required as a coreductant. The subsequent addition of formate or mannitol proved capable of overcoming the total inhibition induced by the mixture of catalase, SOD, and DTPA. The simplest interpretation of the data is that most of the autoxidation of 6HODA, as commonly observed, involves successive reduction of a series of metal-bound species of oxygen; the actual transfer of electrons occurring within a ternary reductant-metal-oxygen transition state.