Neuronal metabotropic glutamate receptor 8 protects against neurodegeneration in CNS inflammation

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system with continuous neuronal loss. Treatment of clinical progression remains challenging due to lack of insights into inflammation-induced neurodegenerative pathways. Here, we show that an imbalance in the neuronal receptor interactome is driving glutamate excitotoxicity in neurons of MS patients and identify the MS risk-associated metabotropic glutamate receptor 8 (GRM8) as a decisive modulator. Mechanistically, GRM8 activation counteracted neuronal cAMP accumulation, thereby directly desensitizing the inositol 1,4,5-trisphosphate receptor (IP3R). This profoundly limited glutamate-induced calcium release from the endoplasmic reticulum and subsequent cell death. Notably, we found Grm8-deficient neurons to be more prone to glutamate excitotoxicity, whereas pharmacological activation of GRM8 augmented neuroprotection in mouse and human neurons as well as in a preclinical mouse model of MS. Thus, we demonstrate that GRM8 conveys neuronal resilience to CNS inflammation and is a promising neuroprotective target with broad therapeutic implications.

Creatine, guanidinoacetate and homoarginine in statin-induced myopathy

Our study evaluated the effect of creatine and homoarginine in AGAT- and GAMT-deficient mice after simvastatin exposure. Balestrino and Adriano suggest that guanidinoacetate might explain the difference between AGAT- and GAMT-deficient mice in simvastatin-induced myopathy. We agree with Balestrino and Adriano that our data shows that (1) creatine possesses a protective potential to ameliorate statin-induced myopathy in humans and mice and (2) homoarginine did not reveal a beneficial effect in statin-induced myopathy. Third, we agree that guanidinoacetate can be phosphorylated and partially compensate for phosphocreatine. In our study, simvastatin-induced damage showed a trend to be less pronounced in GAMT-deficient mice compared with wildtype mice. Therefore, (phospo) guanidinoacetate cannot completely explain the milder phenotype of GAMT-deficient mice, but we agree that it might contribute to ameliorate statin-induced myopathy in GAMT-deficient mice compared with AGAT-deficient mice. Finally, we agree with Balestino and Adriano that AGAT metabolites should further be evaluated as potential treatments in statin-induced myopathy.

Effect of gloved hand disinfection on hand hygiene before infection-prone procedures on a stem cell ward

BACKGROUND

Hand hygiene compliance even before infection-prone procedures (indication 2, 'before aseptic tasks', according to the World Health Organization (WHO)) remains disappointing.

AIM

To improve hand hygiene compliance by implementing gloved hand disinfection as a resource-neutral process optimization strategy.

METHODS

We performed a three-phase intervention study on a stem cell transplant ward. After baseline evaluation of hand hygiene compliance (phase 1) gloved hand disinfection was allowed (phase 2) and restricted (phase 3) to evaluate and differentiate intervention derived from learning and time effects. The incidence of severe infections as well as of hospital-acquired multidrug-resistant bacteria was recorded by active surveillance.

FINDINGS

Hand hygiene compliance improved significantly from 50% to 76% (P < 0.001) when gloved hand disinfection was allowed. The biggest increase was for infection-prone procedures (WHO 2) from 31% to 65%; P < 0.001. Severe infections decreased by trend (from 6.0 to 2.5 per 1000 patient-days) whereas transmission of multidrug-resistant organisms was not affected.

CONCLUSION

Gloved hand disinfection significantly improved compliance with the hand hygiene, especially in activities relevant to infections and infection prevention. Thus, this process optimization may be an additional, easy implementable, resource-neutral tool for a highly vulnerable patient cohort.

A Mouse Model of Creatine Transporter Deficiency Reveals Impaired Motor Function and Muscle Energy Metabolism

Creatine serves as fast energy buffer in organs of high-energy demand such as brain and skeletal muscle. L-Arginine:glycine amidinotransferase (AGAT) and guanidinoacetate N-methyltransferase are responsible for endogenous creatine synthesis. Subsequent uptake into target organs like skeletal muscle, heart and brain is mediated by the creatine transporter (CT1, SLC6A8). Creatine deficiency syndromes are caused by defects of endogenous creatine synthesis or transport and are mainly characterized by intellectual disability, behavioral abnormalities, poorly developed muscle mass, and in some cases also muscle weakness. CT1-deficiency is estimated to be among the most common causes of X-linked intellectual disability and therefore the brain phenotype was the main focus of recent research. Unfortunately, very limited data concerning muscle creatine levels and functions are available from patients with CT1 deficiency. Furthermore, different CT1-deficient mouse models yielded conflicting results and detailed analyses of their muscular phenotype are lacking. Here, we report the generation of a novel CT1-deficient mouse model and characterized the effects of creatine depletion in skeletal muscle. HPLC-analysis showed strongly reduced total creatine levels in skeletal muscle and heart. MR-spectroscopy revealed an almost complete absence of phosphocreatine in skeletal muscle. Increased AGAT expression in skeletal muscle was not sufficient to compensate for insufficient creatine transport. CT1-deficient mice displayed profound impairment of skeletal muscle function and morphology (i.e., reduced strength, reduced endurance, and muscle atrophy). Furthermore, severely altered energy homeostasis was evident on magnetic resonance spectroscopy. Strongly reduced phosphocreatine resulted in decreased ATP/Pi levels despite an increased inorganic phosphate to ATP flux. Concerning glucose metabolism, we show increased glucose transporter type 4 expression in muscle and improved glucose clearance in CT1-deficient mice. These metabolic changes were associated with activation of AMP-activated protein kinase – a central regulator of energy homeostasis. In summary, creatine transporter deficiency resulted in a severe muscle weakness and atrophy despite different compensatory mechanisms.

Tetraphenylporphyrin derivative specifically blocks members of the voltage-gated potassium channel subfamily Kv1

Tetraphenylporphyrin derivatives represent a promising class of high-affinity ligands for voltage-gated potassium (Kv) channels. Herein, we investigated the mode of Kv channel block of one tetraphenylporphyrin derivative, por3, using electrophysiological methods, structure-based mutagenesis, and solid-state NMR spectroscopy. The combined data showed that por3 specifically blocks Kv1.x channels. Unexpectedly, 2 different por3 binding modes lead to Kv1.x channel block exerted through multiple por3 binding sites: first, por3 interacts in a highly cooperative and specific manner with the voltage sensor domain stabilizing closed Kv1 channel state(s). Therefore, stronger depolarization is needed to activate Kv1.x channels in the presence of por3. Second, por3 bind to a single site at the external pore entrance to block the ion conduction pathway of activated Kv1.x channels. This block is voltage-independent. Por3 appears to have equal affinities for voltage-sensor and pore. However, at negative voltage and low por3 concentration, por3 gating modifier properties prevail due to the high cooperativity of binding. By contrast, at positive voltages, when Kv1.x channels are fully activated, por3 pore blocking properties predominate.

Coupling of activation and inactivation gate in a K+-channel: potassium and ligand sensitivity

Potassium (K(+))-channel gating is choreographed by a complex interplay between external stimuli, K(+) concentration and lipidic environment. We combined solid-state NMR and electrophysiological experiments on a chimeric KcsA-Kv1.3 channel to delineate K(+), pH and blocker effects on channel structure and function in a membrane setting. Our data show that pH-induced activation is correlated with protonation of glutamate residues at or near the activation gate. Moreover, K(+) and channel blockers distinctly affect the open probability of both the inactivation gate comprising the selectivity filter of the channel and the activation gate. The results indicate that the two gates are coupled and that effects of the permeant K(+) ion on the inactivation gate modulate activation-gate opening. Our data suggest a mechanism for controlling coordinated and sequential opening and closing of activation and inactivation gates in the K(+)-channel pore.

Toxin-induced conformational changes in a potassium channel revealed by solid-state NMR

The active site of potassium (K+) channels catalyses the transport of K+ ions across the plasma membrane--similar to the catalytic function of the active site of an enzyme--and is inhibited by toxins from scorpion venom. On the basis of the conserved structures of K+ pore regions and scorpion toxins, detailed structures for the K+ channel-scorpion toxin binding interface have been proposed. In these models and in previous solution-state nuclear magnetic resonance (NMR) studies using detergent-solubilized membrane proteins, scorpion toxins were docked to the extracellular entrance of the K+ channel pore assuming rigid, preformed binding sites. Using high-resolution solid-state NMR spectroscopy, here we show that high-affinity binding of the scorpion toxin kaliotoxin to a chimaeric K+ channel (KcsA-Kv1.3) is associated with significant structural rearrangements in both molecules. Our approach involves a combined analysis of chemical shifts and proton-proton distances and demonstrates that solid-state NMR is a sensitive method for analysing the structure of a membrane protein-inhibitor complex. We propose that structural flexibility of the K+ channel and the toxin represents an important determinant for the high specificity of toxin-K+ channel interactions.

Violence between women in an urban emergency department patient population

OBJECTIVE

To determine what percentage of women presenting to an urban emergency department (ED) for any reason had been the victims of violence committed by another woman in the previous year.

METHODS

This was a prospective study of a consecutive sample of female patients of legal age presenting to the ED between 8 AM and 12 midnight over an 11-week period. Patients were asked a series of questions adapted from the George Washington University Universal Violence Prevention Screening Protocol. Non-English-speaking patients, those unable to give informed consent, and those meeting regional criteria for major trauma were excluded.

RESULTS

One thousand six hundred seventy-six women participated; 426 (25%) refused. Of the 1,250 women interviewed, 118 (9.4%; 95% CI = 7.8% to 11.1%) reported being assaulted by another woman in the previous 12 months. Compared with the nonvictims, the victims were more frequently younger and single. The most common forms of assault were slapping, grabbing, and shoving (54.7% of victims). These were followed by being choked, kicked, bitten, or punched (46.2%). Eighteen percent of the assaults involved a weapon or an object. Five percent of the victims described being forced to have sex. Thirty-seven percent of the victims contacted the police, 13% required medical attention, 17% pursued legal action, and 10% sought follow-up counseling.

CONCLUSIONS

Nine percent of the women in the study sample had been assaulted by another woman in the previous year. Further attention to the recognition and management of violence committed by women against other women may be warranted to ensure that patients receive appropriate treatment and referral.

Primary closure of mammalian bites

OBJECTIVE

Suturing of bite wounds remains controversial. The authors evaluated the incidence of wound infection in 145 mammalian bite wounds treated with primary closure.

METHODS

Consecutive patients with bite wounds receiving primary closure at a university hospital ED had structured closed-question data sheets completed at the time of wound management and suture removal. Infection was determined at the time of suture removal using a previously validated definition. Data included demographics; medical history; time from injury to evaluation; wound characteristics and location; details of wound cleansing methods, debridement, foreign body removal, and wound closure methods; use of antibiotics; and follow-up wound evaluation. Proportions and 95% confidence intervals were calculated.

RESULTS

One hundred forty-five mammalian bite patients were enrolled: 88 dog, 45 cat, and 12 human bites. Patients had a mean (+/-SD) age of 21 +/- 20 years; 58% were male; 86% were white; and they presented a mean (+/-SD) of 1.8 +/- 1.2 hours after injury. Bites occurred on the head and neck (57%), upper extremity (36%), and lower extremity (6%). Wounds had a mean length and width of 2.5 cm and 4.8 mm, respectively. Twelve percent involved structures deep to subcutaneous tissue. After primary wound closure, wound infections occurred in eight patients (5.5%; 95% confidence interval = 1.8% to 9.2%).

CONCLUSIONS

The data suggest that carefully selected mammalian bite wounds can be sutured with approximately a 6% rate of infection. This infection rate may be acceptable in lacerations where cosmesis is a primary concern.

History of domestic violence among male patients presenting to an urban emergency department

OBJECTIVE

To establish the prevalence of domestic violence committed by women against male patients presenting to an urban ED for any reason.

METHODS

This was a prospective survey in which male patients of legal age presenting to the ED over a 13-week period were interviewed. Patients answered a series of six questions adapted from the George Washington University Universal Violence Prevention Screening Protocol. Patients who could not speak English, those refusing to participate, those unable to give informed consent, and those meeting regional criteria for major trauma were excluded.

RESULTS

Of 866 male patients interviewed, 109 (12.6%) had been the victims of domestic violence committed by a female intimate partner within the preceding year. Victims were more likely to be younger, single, African American, and uninsured. The most common forms of assault were slapping, grabbing, and shoving (60.6% of victims). These were followed by choking, kicking, biting, and punching (48.6%), or throwing an object at the victim (46.8%). Thirty-seven percent of cases involved a weapon. Seven percent of victims described being forced to have sex. Nineteen percent of victims contacted the police; 14% required medical attention; 11% pressed charges or sought a restraining order; and 6% pursued follow-up counseling.

CONCLUSIONS

Almost 13% of men in this sample population had been victims of domestic violence committed by a female intimate partner within the previous year. Further attention to the recognition and management of domestic violence committed by women against men may be warranted.