Cytosine-based nucleoside analogs are selectively lethal to DNA mismatch repair-deficient tumour cells by enhancing levels of intracellular oxidative stress

BACKGROUND

DNA mismatch repair deficiency is present in a significant proportion of a number of solid tumours and is associated with distinct clinical behaviour.

METHODS

To identify the therapeutic agents that might show selectivity for mismatch repair-deficient tumour cells, we screened a pair of isogenic MLH1-deficient and MLH1-proficient tumour cell lines with a library of clinically used drugs. To test the generality of hits in the screen, selective agents were retested in cells deficient in the MSH2 mismatch repair gene.

RESULTS

We identified cytarabine and other related cytosine-based nucleoside analogues as being selectively toxic to MLH1 and MSH2-deficient tumour cells. The selective cytotoxicity we observed was likely caused by increased levels of cellular oxidative stress, as it could be abrogated by antioxidants.

CONCLUSION

We propose that cytarabine-based chemotherapy regimens may represent a tumour-selective treatment strategy for mismatch repair-deficient cancers.

Postoperative recurrence of Crohn's disease: impact of endoscopic monitoring and treatment step-up

AIM

Eighty per cent of patients with Crohn's disease require surgery, of whom 70% will require a further operation. Recurrence occurs at the anastomosis. Although often recommended, the impact of postoperative colonoscopy and treatment adjustment is unknown.

METHOD

Patients with a bowel resection over a 10-year period were reviewed and comparison made between those who did and did not have a postoperative colonoscopy within 1 year of surgery, and those who did or did not have a step-up in drug therapy.

RESULTS

Of 222 patients operated on, 136 (65 men, mean age 33 years, mean disease duration 8 years, median follow-up 4 years) were studied. Of 70 patients with and 66 without postoperative colonoscopy, clinical recurrence occurred in 49% and 48% (NS) and further surgery in 9% and 5% (NS). Eighty-nine per cent of colonoscoped patients had a decision based on the colonoscopic findings: of these, 24% had a step-up of drug therapy [antibiotics (n =10), aminosalicylates (n=2), thiopurine (n=5), methotrexate (n=1)] and 76% had no step-up in drug therapy. In colonoscoped patients clinical recurrence occurred in 9 (60%) of 15 patients with, and 23 (49%) of 47 without step-up and surgical recurrence in 2 (13%) of 15 and 4 (9%) of 47 (NS).

CONCLUSION

Clinical recurrence occurs in a majority of patients soon after surgery. In this cohort, there was no clinical benefit from colonoscopy or increased drug therapy within 1 year after operation. However, the response to the endoscopic findings was not standardized and immunosuppressive therapy was uncommon. Standardizing timing of colonoscopy and drug therapy, including more intense therapy, may improve outcome, although this remains to be proven.

Phosphorus and calcium retention in steers fed a roughage diet is influenced by dietary 25OH-vitamin D

Active absorption of phosphorus (P) from the alimentary tract is promoted by increased concentrations of active vitamin D [1,25(OH)2D3] in blood; however, the production of this active vitamin is determined by plasma concentrations of calcium (Ca) and not P. As a consequence, diets of adequate Ca content, but insufficient P, will not promote active P absorption. Dietary supplements of 25OH-vitamin D (25OHD), the precursor of 1,25(OH)2D3, may stimulate P absorption and P retention of ruminants consuming diets marginally deficient in P. To evaluate this hypothesis, steers (n = 18) were fed a pelleted low-quality roughage diet containing an adequate Ca concentration (0.68%). Nine steers received a supplement of 25OHD mixed into their feed, at a rate of 3.25 mg/head.day, before pelleting. The other nine steers were fed the Control diet without supplementation. All steers were individually housed for 10 days before being moved into metabolism crates for a further 3-day period. The steers which received the diet containing 25OHD exhibited increased retention of P and Ca, ~4 and 3 g/day, respectively. Blood samples were taken before the adaptation period and then daily during the period in the metabolism crates. Plasma concentrations of both P and Ca were increased by 25OHD supplementation throughout the collection period. Addition of 25OHD to the diet of grazing animals may reduce the need for P supplementation programs and improve productivity.

Interaction between a history of depression and rumination on neural response to emotional faces

BACKGROUND

Both past depressive episodes and the personality trait of depressive rumination are strong risk factors for future depression. Depression is associated with abnormal emotional processing, which may be a neurobiological marker for vulnerability to depression. A consistent picture has yet to emerge as to how a history of depression and the tendency to ruminate influence emotional processing. The aim of this study was to investigate the relationship between rumination, past depression and neural responses when processing face emotions.

METHOD

The Ruminative Responses Scale (RRS) was completed by 30 remitted depressives and 37 controls who underwent functional magnetic resonance imaging (fMRI) scanning while viewing happy, sad, fearful and neutral faces.

RESULTS

The remitted depressives showed overall reductions in neural responses to negative emotions relative to the controls. However, in the remitted depressives, but not the controls, RRS scores were correlated with increased neural responses to negative emotions and decreased responses to happiness in limbic regions.

CONCLUSIONS

Automatic emotion processing biases and rumination seem to be correlated to aspects of vulnerability to depression. However, remission from depression may be maintained by a general suppression of limbic responsiveness to negative emotion.

Attenuated responses to emotional expressions in women with generalized anxiety disorder

BACKGROUND

Generalized anxiety disorder (GAD) is under-researched despite its high prevalence and large impact on the healthcare system. There is a paucity of functional magnetic resonance imaging (fMRI) studies that explore the neural correlates of emotional processing in GAD. The present study investigated the blood oxygen level dependent (BOLD) response to processing positive and negative facial emotions in patients with GAD.

METHOD

A total of 15 female GAD patients and 16 female controls undertook an implicit face emotion task during fMRI scanning. They also performed a face emotion recognition task outside the scanner.

RESULTS

The only behavioural difference observed in GAD patients was less accurate detection of sad facial expressions compared with control participants. However, GAD patients showed an attenuated BOLD signal in the prefrontal cortex to fearful, sad, angry and happy facial expressions and an attenuated signal in the anterior cingulate cortex to happy and fearful facial expressions. No differences were found in amygdala response.

CONCLUSIONS

In contrast with previous research, this study found BOLD signal attenuation in the ventrolateral and medial prefrontal cortex and the anterior cingulate cortex during face emotion processing, consistent with a hypothesis of hypo-responsivity to external emotional stimuli in GAD. These decreases were in areas that have been implicated in emotion and cognition and may reflect an altered balance between internally and externally directed attentional processes.

Assessing clinical outcome after high technology home treatment for cystic fibrosis

Focal points

Neural correlates of choice behavior related to impulsivity and venturesomeness

Impulsivity has been associated with several psychiatric disorders including drug addiction and gambling. Impulsive subjects typically have a preference for short-term over long-term rewards and make risky choices. This study used functional magnetic resonance imaging (fMRI) to investigate the neural correlates of self-rated impulsivity and venturesomeness during tasks involving delayed and risky choice. A broader sampling approach was taken by recruiting participants with behaviors that have been linked to impulsivity (gambling N=15, and recreational drug use N=10) and those without these behaviors (N=9). Selection between delayed or probabilistic rewards was associated with activation in fronto-parietal regions in line with previous research. When selecting between delayed rewards, activity within the pregenual anterior cingulate cortex and ventrolateral prefrontal cortex correlated positively with impulsivity scores while activity within the orbitofrontal cortex, subgenual anterior cingulate cortex and caudate correlated positively with venturesomeness scores. Selection between probabilistic rewards revealed no correlation between scores and regional activations. The results from this study provide targets for future research investigating the neural substrates of impulsivity. They also provide targets for the further investigation into the pathophysiology of addiction and impulse-control disorders.

The Micronutrient Genomics Project: a community-driven knowledge base for micronutrient research

Micronutrients influence multiple metabolic pathways including oxidative and inflammatory processes. Optimum micronutrient supply is important for the maintenance of homeostasis in metabolism and, ultimately, for maintaining good health. With advances in systems biology and genomics technologies, it is becoming feasible to assess the activity of single and multiple micronutrients in their complete biological context. Existing research collects fragments of information, which are not stored systematically and are thus not optimally disseminated. The Micronutrient Genomics Project (MGP) was established as a community-driven project to facilitate the development of systematic capture, storage, management, analyses, and dissemination of data and knowledge generated by biological studies focused on micronutrient–genome interactions. Specifically, the MGP creates a public portal and open-source bioinformatics toolbox for all “omics” information and evaluation of micronutrient and health studies. The core of the project focuses on access to, and visualization of, genetic/genomic, transcriptomic, proteomic and metabolomic information related to micronutrients. For each micronutrient, an expert group is or will be established combining the various relevant areas (including genetics, nutrition, biochemistry, and epidemiology). Each expert group will (1) collect all available knowledge, (2) collaborate with bioinformatics teams towards constructing the pathways and biological networks, and (3) publish their findings on a regular basis. The project is coordinated in a transparent manner, regular meetings are organized and dissemination is arranged through tools, a toolbox web portal, a communications website and dedicated publications.

Hedonic and informational functions of the human orbitofrontal cortex

Functional imaging studies have revealed roles for orbitofrontal cortex (OFC) in reward processing and decision making. In many situations, rewards signal that the current behavior should be maintained, whereas punishments cue a change in behavior. Thus, hedonic responses to reinforcers are conflated with their function as behavioral cues. In an attempt to disambiguate these functions, we performed a functional magnetic resonance imaging study of a 2-choice decision-making task. After each trial, subjects were rewarded or punished and independently provided with a cue to maintain or change behavior. We identified key regions of OFC involved in these processes. An anterior medial focus responded to reward, whereas bilateral lateral foci responded to punishment. The right-sided lateral region that responded to punishment also responded to cues for behavior change (shift), whereas a more ventral and anterior bilateral region responded to cues for behavioral maintenance (stay). The right-sided stay region responded specifically when stay cues were combined with punishment. These results support the view that OFC codes both hedonic responses to reinforcers and their behavioral consequences. Punishments and shift cues are associated with the same right lateral OFC focus, suggesting a fundamental connection between emotive response to negative reinforcement and use of negative information to cue behavioral change.

Inhibitory effect of calcium on non-heme iron absorption may be related to translocation of DMT-1 at the apical membrane of enterocytes

Many studies show that calcium reduces iron absorption from single meals, but the underlying mechanism is not known. We tested the hypothesis that calcium alters the expression and/or functionality of iron transport proteins. Differentiated Caco-2 cells were treated with ferric ammonium citrate and calcium chloride, and ferritin, DMT-1, and ferroportin were quantified in whole-cell lysate and cell-membrane fractions. Calcium attenuated the iron-induced increase in cell ferritin levels in a dose-dependent manner; a significant decrease was seen at calcium concentrations of 1.25 and 2.5 mM but was only evident after a 16-24 h incubation period. Calcium and iron treatments decreased DMT-1 protein in Caco-2 cell membranes, although total DMT-1 in whole cell lysates was unchanged by either iron or calcium. No change was seen in ferroportin expression. Our data suggest that calcium reduces iron bioavailability by decreasing DMT-1 expression at the apical cell membrane, thereby downregulating iron transport into the cell.