Gina Hadley

Tsc1 (hamartin) confers neuroprotection against ischemia by inducing autophagy

Previous attempts to identify neuroprotective targets by studying the ischemic cascade and devising ways to suppress it have failed to translate to efficacious therapies for acute ischemic stroke. We hypothesized that studying the molecular determinants of endogenous neuroprotection in two well-established paradigms, the resistance of CA3 hippocampal neurons to global ischemia and the tolerance conferred by ischemic preconditioning (IPC), would reveal new neuroprotective targets. We found that the product of the tuberous sclerosis complex 1 gene (TSC1), hamartin, is selectively induced by ischemia in hippocampal CA3 neurons. In CA1 neurons, hamartin was unaffected by ischemia but was upregulated by IPC preceding ischemia, which protects the otherwise vulnerable CA1 cells. Suppression of hamartin expression with TSC1 shRNA viral vectors both in vitro and in vivo increased the vulnerability of neurons to cell death following oxygen glucose deprivation (OGD) and ischemia. In vivo, suppression of TSC1 expression increased locomotor activity and decreased habituation in a hippocampal-dependent task. Overexpression of hamartin increased resistance to OGD by inducing productive autophagy through an mTORC1-dependent mechanism.

A systematic review and meta-analysis of randomized controlled trials of endovascular thrombectomy compared with best medical treatment for acute ischemic stroke.

Background Acute ischemic strokes involving occlusion of large vessels usually recanalize poorly following treatment with intravenous thrombolysis. Recent studies have shown higher recanalization and higher good outcome rates with endovascular therapy compared with best medical management alone. A systematic review and meta-analysis investigating the benefits of all randomized controlled trials of endovascular thrombectomy where at least 25% of patients were treated with a thrombectomy device for the treatment of acute ischemic stroke compared with best medical treatment have yet to be performed. Aim To perform a systematic review and a meta-analysis evaluating the effectiveness of endovascular thrombectomy compared with best medical care for treatment of acute ischemic stroke. Summary of review Our search identified 437 publications, from which eight studies (totaling 2423 patients) matched the inclusion criteria. Overall, endovascular thrombectomy was associated with improved functional outcomes (modified Rankin Scale 0–2) [odds ratio 1·56 (1·32–1·85), P < 0·00001]. There was a tendency toward decreased mortality [odds ratio 0·84 (0·67–1·05), P = 0·12], and symptomatic intracerebral hemorrhage was not increased [odds ratio 1·03 (0·71–1·49), P = 0·88] compared with best medical management alone. The odds ratio for a favorable functional outcome increased to 2·23 (1·77–2·81, P < 0·00001) when newer generation thrombectomy devices were used in greater than 50% of the cases in each trial. Conclusions There is clear evidence for improvement in functional independence with endovascular thrombectomy compared with standard medical care, suggesting that endovascular thrombectomy should be considered the standard effective treatment alongside thombolysis in eligible patients.

How useful are systematic reviews for informing palliative care practice? Survey of 25 Cochrane systematic reviews

BackgroundIn contemporary medical research, randomised controlled trials are seen as the gold standard for establishing treatment effects where it is ethical and practical to conduct them. In palliative care such trials are often impractical, unethical, or extremely difficult, with multiple methodological problems. We review the utility of Cochrane reviews in informing palliative care practice.MethodsPublished reviews in palliative care registered with the Cochrane Pain, Palliative and Supportive Care Group as of December 2007 were obtained from the Cochrane Database of Systematic Reviews, issue 1, 2008. We reviewed the quality and quantity of primary studies available for each review, assessed the quality of the review process, and judged the strength of the evidence presented. There was no prior intention to perform any statistical analyses.Results25 published systematic reviews were identified. Numbers of included trials ranged from none to 54. Within each review, included trials were heterogeneous with respect to patients, interventions, and outcomes, and the number of patients contributing to any single analysis was generally much lower than the total included in the review. A variety of tools were used to assess trial quality; seven reviews did not use this information to exclude low quality studies, weight analyses, or perform sensitivity analysis for effect of low quality. Authors indicated that there were frequently major problems with the primary studies, individually or in aggregate. Our judgment was that the reviewing process was generally good in these reviews, and that conclusions were limited by the number, size, quality and validity of the primary studies.We judged the evidence about 23 of the 25 interventions to be weak. Two reviews had stronger evidence, but with limitations due to methodological heterogeneity or definition of outcomes. No review provided strong evidence of no effect.ConclusionCochrane reviews in palliative care are well performed, but fail to provide good evidence for clinical practice because the primary studies are few in number, small, clinically heterogeneous, and of poor quality and external validity. They are useful in highlighting the weakness of the evidence base and problems in performing trials in palliative care.

Neuroprotection in stroke: the importance of collaboration and reproducibility

Acute ischaemic stroke accounts for 6.5 million deaths per year, and by 2030 will result in the annual loss of over 200 million disability-adjusted life years globally. There have been considerable recent advances in the gold standard of acute ischaemic stroke treatment, some aspects of which-aspirin to prevent recurrence, and treating patients in specialized stroke wards-are widely applicable. Recanalization of the occluded artery through thrombolysis and/or endovascular thrombectomy is restricted to only a small proportion of patients, due to contra-indications and the costs associated with establishing the infrastructure to deliver these treatments. The use of neuroprotective agents in stroke has been a notable failure of translation from medical research into clinical practice. Yet, with the advent of endovascular thrombectomy and the ability to investigate patients in much greater detail through advanced imaging modalities, neuroprotective agents can and should be re-examined as adjunct therapies to recanalization. In parallel, this requires appropriate planning on behalf of the preclinical stroke research community: there is a need to reinvestigate these therapies in a more collaborative manner, to enhance reproducibility through reduced attrition, improved reporting, and adopting an approach to target validation that more closely mimics clinical trials. This review will describe some of the novel strategies being used in stroke research, and focus on a few key examples of neuroprotective agents that are showing newfound promise in preclinical models of stroke therapy. Our primary aim is to give an overview of some of the challenges faced by preclinical stroke research, and suggest potential ways to improve translational success.

The transient intraluminal filament middle cerebral artery occlusion model as a model of endovascular thrombectomy in stroke

The clinical relevance of the transient intraluminal filament model of middle cerebral artery occlusion (tMCAO) has been questioned due to distinct cerebral blood flow profiles upon reperfusion between tMCAO (abrupt reperfusion) and alteplase treatment (gradual reperfusion), resulting in differing pathophysiologies. Positive results from recent endovascular thrombectomy trials, where the occluding clot is mechanically removed, could revolutionize stroke treatment. The rapid cerebral blood flow restoration in both tMCAO and endovascular thrombectomy provides clinical relevance for this pre-clinical model. Any future clinical trials of neuroprotective agents as adjuncts to endovascular thrombectomy should consider tMCAO as the model of choice to determine pre-clinical efficacy.

Can Observational Studies Provide a Realistic Alternative to Randomized Controlled Trials in Palliative Care

Evidence-based medicine demands ‘gold standard’ randomized controlled trials (RCTs). If strict criteria of quality, validity, and size are met, observational studies give the same result. Given the dearth of RCTs in palliative care, our aim was to identify good observational studies using PubMed searches and e-mail letters to experts in palliative care. The prior intention was provide the most comprehensive description possible to date of observational studies in palliative care, rather than to perform any statistical analyses. Three hundred and forty abstracts of study reports were identified, of which 27% (91) included ≥ 200 subjects and 8% (27) ≥ 1000 subjects. In reports with ≥ 200 subjects, 51% included only cancer patients, and 42% included heterogeneous ‘palliative care’ patients. Prospective and retrospective studies accounted for 38% and 32% of all reports with ≥ 200 subjects. In reports with ≥ 1000 subjects, 59% were retrospective and 19% prospective. Patients had some input in 26% of studies with ≥ 200 subjects, and 15% with ≥ 1000 subjects. Only 12 prospective reports had one specific intervention. We found that palliative care is deficient not only in RCTs, but also good quality observational studies. Those that exist are extremely heterogeneous in subject, design, outcome reporting, and intervention.

Reality of evidence-based practice in palliative care

There has been a paradigm shift in medicine away from tradition, anecdote and theoretical reasoning from the basic sciences towards evidence-based medicine (EBM). In palliative care however, statistically significant benefits may be marginal and may not be related to clinical meaningfulness. The typical treatment vs. placebo comparison necessitated by ‘gold standard’ randomised controlled trials (RCTs) is not necessarily applicable. The complex multimorbidity of end of life care involves considerations of the patient’s physical, psychological, social and spiritual needs. In addition, the field of palliative care covers a heterogeneous group of chronic and incurable diseases no longer limited to cancer. Adequate sample sizes can be difficult to achieve, reducing the power of studies and high attrition rates can result in inadequate follow up periods. This review uses examples of the management of cancer-related fatigue and death rattle (noisy breathing) to demonstrate the current state of EBM in palliative care. The future of EBM in palliative care needs to be as diverse as the patients who ultimately derive benefit. Non-RCT methodologies of equivalent quality, validity and size conducted by collaborative research networks using a ‘mixed methods approach’ are likely to pose the correct clinical questions and derive evidence-based yet clinically relevant outcomes.

Suppression of the inflammatory response by diphenyleneiodonium after transient focal cerebral ischemia

Diphenyleneiodonium (DPI), a NADPH oxidase inhibitor, reduces production of reactive oxygen species (ROS) and confers neuroprotection to focal cerebral ischemia. Our objective was to investigate whether the neuroprotective action of DPI extends to averting the immune response. DPI‐induced gene changes were analyzed by microarray analysis from rat brains subjected to 90 min of middle cerebral artery occlusion, treated with NaCl (ischemia), dimethylsulfoxide (DMSO), or DMSO and DPI (DPI), and reperfused for 48 h. The genomic expression profile was compared between groups using ingenuity pathway analysis at the pathway and network level. DPI selectively up‐regulated 23 genes and down‐regulated 75 genes more than twofold compared with both DMSO and ischemia. It significantly suppressed inducible nitric oxide synthase signaling and increased the expression of methionine adenosyltransferasesynthetase 2A and adenosylmethionine decarboxylase 1 genes, which are involved in increasing the production of the antioxidant glutathione. The most significantly affected gene network comprised genes implicated in the inflammatory response with an expression change indicating an overall suppression. Both integrin‐ and interleukin‐17A‐signaling pathways were also significantly associated and suppressed. In conclusion, the neuroprotective effects of DPI are mediated not only by suppressing ischemia‐triggered oxidative stress but also by limiting leukocyte migration and infiltration.

The role of the endoplasmic reticulum stress response following cerebral ischemia

Background Cornu ammonis 3 (CA3) hippocampal neurons are resistant to global ischemia, whereas cornu ammonis (CA1) 1 neurons are vulnerable. Hamartin expression in CA3 neurons mediates this endogenous resistance via productive autophagy. Neurons lacking hamartin demonstrate exacerbated endoplasmic reticulum stress and increased cell death. We investigated endoplasmic reticulum stress responses in CA1 and CA3 regions following global cerebral ischemia, and whether pharmacological modulation of endoplasmic reticulum stress or autophagy altered neuronal viability. Methods In vivo: male Wistar rats underwent sham or 10 min of transient global cerebral ischemia. CA1 and CA3 areas were microdissected and endoplasmic reticulum stress protein expression quantified at 3 h and 12 h of reperfusion. In vitro: primary neuronal cultures (E18 Wistar rat embryos) were exposed to 2 h of oxygen and glucose deprivation or normoxia in the presence of an endoplasmic reticulum stress inducer (thapsigargin or tunicamycin), an endoplasmic reticulum stress inhibitor (salubrinal or 4-phenylbutyric acid), an autophagy inducer ([4′-(N-diethylamino) butyl]-2-chlorophenoxazine (10-NCP)) or autophagy inhibitor (3-methyladenine). Results In vivo, decreased endoplasmic reticulum stress protein expression (phospho-eIF2α and ATF4) was observed at 3 h of reperfusion in CA3 neurons following ischemia, and increased in CA1 neurons at 12 h of reperfusion. In vitro, endoplasmic reticulum stress inducers and high doses of the endoplasmic reticulum stress inhibitors also increased cell death. Both induction and inhibition of autophagy also increased cell death. Conclusion Endoplasmic reticulum stress is associated with neuronal cell death following ischemia. Neither reduction of endoplasmic reticulum stress nor induction of autophagy demonstrated neuroprotection in vitro, highlighting their complex role in neuronal biology following ischemia.

Reply: Intravenous thrombolysis for ischaemic strokes: a call for reappraisal

Sir, Many thanks for giving us the opportunity to reply to the letter in reference to our review ‘The exact science of stroke thrombolysis and the quiet art of patient selection’ (Balami et al. , 2013). Aside from well documented limitations, recombinant tissue plasminogen activator (rt-PA, alteplase) remains the only evidence-based treatment in acute ischaemic stroke (Balami et al. , 2013) with evidence dating back to 1995 for clinical efficacy (NINDS, 1995). In recent meta-analyses containing in excess of 6500 patients, alteplase significantly increases the chance of a favourable stroke outcome if administered within 4.5 h (Wardlaw et al. , 2012; Emberson et al. , 2014). The most established complication from alteplase treatment is bleeding risk, but there is growing evidence that physicians are more liable to lawsuits for failure to use rt-PA than from complications related to therapy (Liang et al. , 2008; Bruce et al. , 2011). We agree with Bhagavati (2014) in that many studies did not carry out assessment of recanalization using the most appropriate methods. This may be down to many reasons including technology and equipment available at the time, purpose of the trial, time, …