Identification and characterisation of functional Kir6.1-containing ATP-sensitive potassium channels in the cardiac ventricular sarcolemmal membrane

BACKGROUND AND PURPOSE

The canonical Kir6.2/SUR2A ventricular KATP channel is highly ATP-sensitive and remains closed under normal physiological conditions. These channels activate only when prolonged metabolic compromise causes significant ATP depletion and then shortens the action potential to reduce contractile activity. Pharmacological activation of KATP channels is cardioprotective, but physiologically, it is difficult to understand how these channels protect the heart if they only open under extreme metabolic stress. The presence of a second KATP channel population could help explain this. Here, we characterise the biophysical and pharmacological behaviours of a constitutively active Kir6.1-containing KATP channel in ventricular cardiomyocytes.

EXPERIMENTAL APPROACH

Patch-clamp recordings from rat ventricular myocytes in combination with well-defined pharmacological modulators was used to characterise these newly identified K+ channels. Action potential recording, calcium (Fluo-4) fluorescence measurements and video edge detection of contractile function were used to assess functional consequences of channel modulation.

KEY RESULTS

Our data show a ventricular K+ conductance whose biophysical characteristics and response to pharmacological modulation were consistent with Kir6.1-containing channels. These Kir6.1-containing channels lack the ATP-sensitivity of the canonical channels and are constitutively active.

CONCLUSION AND IMPLICATIONS

We conclude there are two functionally distinct populations of ventricular KATP channels: constitutively active Kir6.1-containing channels that play an important role in fine-tuning the action potential and Kir6.2/SUR2A channels that activate with prolonged ischaemia to impart late-stage protection against catastrophic ATP depletion. Further research is required to determine whether Kir6.1 is an overlooked target in Comprehensive in vitro Proarrhythmia Assay (CiPA) cardiac safety screens.

Factors influencing nodal yield in neck dissections for head and neck malignancies

OBJECTIVE

A standard lateral neck dissection should yield at least 18 lymph nodes. The goal of the present study was to examine what factors might influence the number of lymph nodes retrieved during a neck dissection.

METHODS

This was a retrospective cohort study in a tertiary academic referral centre for head and neck oncology. Two hundred and nineteen consecutive neck dissections were examined. Age of the patient and primary site were recorded, along with tumour histology, previous radiotherapy and final nodal count.

RESULTS

The mean age was 62.2 ± 13.0 years. The most common primary site was the oral cavity (38.8 per cent). The mean number of lymph nodes was 30.63 ± 13.9. In total, 17.8 per cent had undergone previous radiotherapy. The mean number of lymph nodes was 33.26 ± 13.27 in patients with no previous radiation exposure and 18.47 ± 9.46 in those with previous radiation treatment.

CONCLUSION

Lymph node yield from a neck dissection is likely multi-factorial in nature. Previous radiotherapy, the only significant contributor, led to a mean reduction of lymph node yield from 33.3 to 18.5.

Slowly activating voltage-gated potassium current potentiation by ML277 is a novel cardioprotective intervention

Cardiovascular disease is thought to account for nearly a third of deaths worldwide, with ischemic heart disease, including acute coronary syndromes such as myocardial infarction, accounting for 1.7 million deaths per year. There is a clear need for interventions to impart cardioprotection against ischemia. Here, we show that the slowly activating voltage-gated potassium current (IKs) potentiator ML277 imparts cardioprotection against ischemia in cellular and whole-heart models by modulating the action potential duration. In three different metabolic inhibition and reperfusion models, an increased contractile recovery and cell survival was observed with ML277, indicative of protection. Finally, ML277 reduced infarct size in an ex vivo Langendorff coronary ligation model, including if only applied on reperfusion. In conclusion, potentiation of the IKs with ML277 imparted a cardioprotection that was equivalent to the protection reported previously by ischemic preconditioning. These data suggest that IKs potentiation may be therapeutically useful in acute coronary syndromes.

Provision of smoking cessation support for patients following a diagnosis of cancer in Ireland

There is growing evidence that smoking cessation (SC) improves outcomes following diagnosis of cancer. Notwithstanding adverse outcomes, a significant number of those diagnosed with cancer continue to smoke. Our objective was to document the SC services provided for patients with cancer by specialist adult cancer hospitals across Ireland, a country with a stated tobacco endgame goal. A cross-sectional survey based on recent national clinical guidelines was used to determine SC care delivery across eight adult cancer specialist hospitals, and one specialist radiotherapy centre. Qualtrics was used. The response rate was 88.9% with data reported from seven cancer hospitals and one specialist radiotherapy centre, all indicating they had some SC related provision (100%). Stop smoking medications were provided to cancer inpatients in two hospitals, at outpatients and attending day ward services in one hospital. Smokers with cancer were referred automatically to the SC service in two hospitals at diagnosis. While stop smoking medications were available 24 h a day in five hospitals, most did not stock all three (Nicotine Replacement Therapy, Bupropion, Varenicline). One hospital advised they had data on uptake of SC services for smokers with cancer but were unable to provide detail. There is considerable variation in SC information and services provided to cancer patients across adult cancer specialist centres in Ireland, reflecting the suboptimal practice of smoking cessation for patients with cancer found in the limited international audits. Such audits are essential to demonstrate service gaps and provide a baseline for service improvement.

Smoking cessation for cancer patients through the lens of cancer specialists: challenges & solutions

Background

The benefits of smoking cessation (SC) for cancer patients are widely recognised. However, there has been a limited emphasis on SC in this context and it continues to be a challenge for cancer patients. As part of a larger feasibility study aiming to develop a structured SC pathway for cancer patients in Ireland, this qualitative study explored the SC practices, experiences and opinions of oncology healthcare professionals (HCPs).

Methods

Semi-structured interviews were conducted with 18 HCPs from lung, breast, cervical, head and neck and general oncology, across 4 specialist adult cancer hospitals in Ireland. Interview transcripts were analysed using thematic analysis.

Results

Four key themes emerged:

(1) Frequently ask and advise but infrequently assist: most HCPs ask about smoking and many advise about available supports, but few refer patients to SC services. Where offered, referrals were to hospital SC services and/or nicotine replacement therapy was prescribed; no HCP prescribed varenicline or bupropion. Barriers included lack of time, ill-defined referral pathways and lack of knowledge.

(2) Increased willingness but differing ability to quit: most patients were interested in quitting post diagnosis and had varying support needs, linked to cancer stage, social circumstances and stress levels.

(3) Need for an integrated or parallel service: all HCPs suggested that a structured and defined referral pathway will facilitate SC.

(4) Motivational counselling and pharmacotherapy combination: many HCPs suggested face to face as the best mode of intervention initially, with regular follow ups and ongoing support virtually, started pre-treatment, with an empathetic and empowering approach with provision of both motivational counselling and SC pharmacotherapy.

Conclusions

Smoking post cancer diagnosis has serious implications for cancer treatment and prognosis but is frequently overlooked. These findings will inform the design of a SC pathway for cancer patients.

Key messages

• Despite increased willingness to quit, there is inadequate and inconsistent SC support provision for cancer patients.

• Tailored SC support should be an integral part of comprehensive cancer care.

Impact of antihypertensive medication regimens on blood pressure control in individuals with established coronary heart disease

Background and purpose

Hypertension is a major risk factor for coronary heart disease (CHD) development and progression, with pharmacological control of blood pressure reducing the risk of CHD events and death [1].

Treatment and control of blood pressure in CHD is suboptimal, with many patients failing to achieve guideline-directed targets [1,2]. This study aims to assess the relationship between antihypertensive medication regimens and blood pressure control in patients with hypertension and established coronary heart disease.

Methods

The iASPIRE study recently evaluated secondary prevention in an Irish cohort with coronary heart disease [2]. Based on a method used in a similar study [3], we calculated the average percentage daily dose of each prescribed antihypertensive agent. We then assessed the relationship between dose and number of antihypertensive agents with blood pressure control.

Results

540 (75.5%) of iASPIRE participants had an underlying diagnosis of hypertension, and at the study examination, 56% of these had a blood pressure ≥140/90 mmHg, while 83% had a blood pressure ≥130/80 mmHg. The median number of antihypertensive agents prescribed was 2 (IQR 1–2), with 88% of those with hypertension on at least one blood pressure medication. In participants with hypertension on treatment, the median percentage daily medication dose was 29% (IQR 14–50). After adjustment for age and sex, the addition of further antihypertensive medications increased the odds of achieving a blood pressure target of <130/80 mmHg (OR 1.3, 95% CI 1.07–1.69, p=0.012). The average percentage daily dose of each antihypertensive agent was lower in both participants with a medication-controlled blood pressure of <130/80 mmHg and <140/90 mmHg compared to those without blood pressure control (30% versus 37% p=0.006 and 33% versus 38% p=0.028 respectively).

Conclusion

Many patients with hypertension and coronary heart disease currently fail to achieve blood pressure control. This analysis found that an increasing number of antihypertensive medications but not increasing dose was associated with better blood pressure control. Combination therapy is superior to sequential monotherapy in the treatment of hypertension [1], and an approach that emphasises the initiation of several antihypertensive agents would likely lead to better blood pressure control in individuals with coronary heart disease.

Funding Acknowledgement

Type of funding sources: None.

Selective protein kinase C inhibition switches time-dependent glucose cardiotoxicity to cardioprotection

Hyperglycaemia at the time of myocardial infarction has an adverse effect on prognosis irrespective of a prior diagnosis of diabetes, suggesting glucose is the damaging factor. In ex vivo models of ischaemia, we demonstrated that deleterious effects of acutely elevated glucose are PKCα/β-dependent, and providing PKCα/β are inhibited, elevated glucose confers cardioprotection. Short pre-treatments with high glucose were used to investigate time-dependent glucose cardiotoxicity, with PKCα/β inhibition investigated as a potential mechanism to reverse the toxicity. Freshly isolated non-diabetic rat cardiomyocytes were exposed to elevated glucose to investigate the time-dependence toxic effects. High glucose challenge for >7.5 min was cardiotoxic, proarrhythmic and lead to contractile failure, whilst cardiomyocytes exposed to metabolic inhibition following 5-min high glucose, displayed a time-dependent protection lasting ∼15 min. This protection was further enhanced with PKCα/β inhibition. Cardioprotection was measured as a delay in contractile failure and K_ATP channel activation, improved contractile and Ca²⁺ transient recovery and increased cell survival. Finally, the effects of pre-ischaemic treatment with high glucose in a whole-heart coronary ligation protocol, where protection was evident with PKCα/β inhibition. Selective PKCα/β inhibition enhances protection suggesting glycaemic control with PKC inhibition as a potential cardioprotective therapeutics in myocardial infarction and elective cardiac surgery.

The demographic, psychosocial and clinical characteristics associated with cardiac risk factor control: an analysis of secondary prevention in adults with established coronary heart disease

Funding Acknowledgements

Type of funding sources: None.

Background and Purpose

Achieving risk factor (RF) control in patients with established coronary heart disease (CHD) reduces the risk of CHD events.(1) Cross-sectional studies have shown that the implementation of current prevention guidelines is poor, with most patients failing to meet recommended targets.(2,3) This study aims to identify demographic, psychosocial and clinical characteristics associated with the non-achievement of RF targets in a population with CHD.

Methods

In this post-hoc cross-sectional analysis, multivariable logistic regression identified characteristics significantly associated with poor RF control in participants of the iASPIRE study which recently assessed secondary CHD prevention in Ireland.

Results

An unhealthy diet (Odds Ratio [OR] 1.6, 95% CI 1.1-2.4, p=0.015), male sex (OR 1.8, 95% CI 1.2-2.8, p=0.007) and type of acute coronary syndrome event (OR 0.6, 95% CI 0.4-0.9, p=0.012) were associated with failure to achieve blood pressure recommendations. Female sex (OR 2.3, 95% CI 1.4-3.8, p=0.002), lack of high-intensity statin (OR 2.4, 95% CI 1.5-3.8, p<0.001) and recurrent hospitalisation for CHD (OR 1.9, 95% CI 1.3-2.8, p=0.001) were associated with poor LDL-C control. Decreasing age (OR 0.9, 95% CI 0.9-1.0, p=0.018), marriage (OR 4.3, 95% CI 1.5-12.1, p=0.007) and insulin use (OR 9.7, 95% CI 1.9-50.4, p=0.007) were associated with a HbA1c of ≥53mmol/mol. The absence of a longstanding illness or disability and decreasing resting heart rate were associated with composite RF control.

Conclusion

Several demographic, psychosocial and clinical characteristics are associated with achieving guideline-recommended RF targets. These findings will support the development of targeted solutions that will improve guideline implementation and the practice of CHD prevention in a high-risk population.

Bempedoic acid and PCSK9 inhibitor eligibility in a contemporary population with atherosclerotic cardiovascular disease

Funding Acknowledgements

Type of funding sources: None.

Background and Purpose

The reduction of low-density lipoprotein cholesterol (LDL-C) in patients with established coronary heart disease (CHD) reduces the risk of atherosclerotic cardiovascular disease (ASCVD) events.(1) Many CHD patients fail to achieve guideline-recommended LDL-C targets without prohibitively expensive proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9 inhibitors).(2, 3, 4) This study aims to assess the impact that bempedoic acid may have on PCSK9 inhibitor eligibility in a population with CHD and ascertain whether its universal adoption would lead to overall cost-savings and a cost-effective reduction in ASCVD events.

Methods and Results

This retrospective analysis included 635 participants from the iASPIRE study, which recently assessed secondary prevention in an Irish cohort of CHD patients. We applied the 2019 ESC/EAS dyslipidaemia guideline LDL-C target of <1.4mmol/L and simulated the average treatment effect of improved lipid-lowering therapy with statins, ezetimibe and bempedoic acid. 86.3% of iASPIRE participants did not have LDL-C control and qualified for treatment intensification. Optimisation of statin therapy would allow 24.4% of patients to achieve their LDL-C goal, while the addition of ezetimibe would improve this to 55.7% leaving 44.3% eligible for a PCSK9 inhibitor. Utilising bempedoic acid would further reduce the proportion eligible to 18.7%. Based on current market prices and the universal application of ESC/EAS recommendations,(1, 5) the adoption of bempedoic acid would reduce the annual treatment costs associated with PCSK9 inhibitor use by almost 50% and result in cost savings per prevented CVD event.

Conclusions

The vast majority of CHD patients currently fail to achieve the recommended LDL-C target in everyday clinical practice. Ezetimibe and optimised statin therapy would enable most patients to meet their LDL-C goal. Employing bempedoic acid in patients with poor LDL-C control would significantly reduce the requirement for PCSK9 inhibitors and lead to cost savings per prevented CVD event.

Oro-Naso-Sino-Orbital-Cutaneous Fistula From Prolonged Cocaine Use

Presentation We present the case of a 48-year-old man with nasal cellulitis and subsequent oro-naso-sino-orbital-cutaneous fistula from prolonged cocaine use. Diagnosis Initial laboratory investigations reported a raised white cell count (WBC) and C-Reactive Protein (CRP) and subsequently a positive atypical anti-neutrophil cytoplasm antibodies (ANCA) and positive anti-proteinase (PR3). Perihilar lung nodularity on chest imaging raised the possibility of a systemic autoimmune response. His urinalysis was positive for cocaine. Treatment He was commenced on Augmentin, Amphotericin B and Prednisolone. An obturator was created to manage the oro-nasal fistula. A subsequent naso-cutaneous defect was re-approximated. Daily nasal saline douche and abstinence of cocaine were recommended. Discussion Cocaine use in the community is rising and poses a challenge to multiple facets of our health care system.

Mortality and long-term outcomes of palliative inotropes in ischemic and non-ischemic cardiomyopathy

Background

Palliative inotropes are frequently utilized for symptom management in patients with end stage heart failure who are unable to undergo durable advanced heart failure therapies. With the advent of improved medical management and early intervention, palliative inotropes may allow for improved patient outcomes than seen previously. In this study, we aim to investigate the survival and outcomes of palliative inotrope therapy and its impacts on ischemic versus non-ischemic cardiomyopathy.

Methods

We retrospectively analyzed 220 patients with American Heart Association Stage D heart failure who were discharged with palliative inotrope therapy after January 1, 2010. Patients who underwent mechanical circulatory support (MCS) or those who underwent heart transplant were excluded. Those with a history of coronary artery disease, myocardial infarction, history of percutaneous intervention, or coronary artery bypass grafting were assigned to ischemic cardiomyopathy (ICM), while patients without these findings were assigned to non-ischemic cardiomyopathy (NICM). Statistical analysis was completed using Chi-Square and Student's t-tests, wherein p<0.05 was considered statistically significant.

Results

Of the 220 patients, 87 had NICM as opposed to 133 with ICM. Mean age was found to be higher among patients with ICM (70 [62–79]) compared to NICM (65 [55–72], p-value <0.01). No significant difference was seen in total days on inotrope therapy (p=0.6). While more patients in both groups were placed on milrinone as opposed to dobutamine, there was no difference between patients with ischemic and NICM (p=0.66 and 0.51 respectively). Although a greater number of patients with NICM had been lost to follow up, admitted to hospice, or expired at 2 years (p<0.01), survival at 3 months, 1 year, and 2 years showed no difference between both groups. No difference was seen in number of hospitalizations or clinic visits in one year. Both groups had similar complication rates with intravenous-access related PICC line infections and new arrhythmias. (See Table).

Conclusion

Despite more frequent use of durable mechanical support devices, many patients who are deemed unsuitable for invasive measures are treated with palliative inotrope therapy. We have found that there is no significant difference in survival, complications, and outcomes of patients on palliative inotropes among ischemic and NICM. These findings show the versatility of palliative inotrope therapy in end stage heart failure. Further studies with larger populations need to be evaluated.

Funding Acknowledgement

Type of funding sources: None.

Title: Characterizing environmental stress responses of aposymbiotic Astrangia poculata to divergent thermal challenges

Anthropogenic climate change threatens corals globally and both high and low temperatures are known to induce coral bleaching. However, coral stress responses across wide thermal breadths remain understudied. Disentangling the role of symbiosis on the stress response in obligately symbiotic corals is challenging because this response is inherently coupled with nutritional stress. Here, we leverage aposymbiotic colonies of the facultatively symbiotic coral, Astrangia poculata, which lives naturally with and without its algal symbionts, to examine how broad thermal challenges influence coral hosts in the absence of symbiosis. A. poculata were collected from their northern range limit and thermally challenged in two independent 16-day common garden experiments (heat and cold challenge) and behavioral responses to food stimuli and genome-wide gene expression profiling (TagSeq) were performed. Both thermal challenges elicited significant reductions in polyp extension. However, there were five times as many differentially expressed genes (DEGs) under cold challenge compared to heat challenge. Despite an overall stronger response to cold challenge, there was significant overlap in DEGs between thermal challenges. We contrasted these responses to a previously identified module of genes associated with the environmental stress response (ESR) in tropical reef-building corals. Cold challenged corals exhibited a pattern consistent with more severe stressors while the heat challenge response was consistent with lower intensity stressors. Given that these responses were observed in aposymbiotic colonies, many genes previously implicated in ESRs in tropical symbiotic species may represent the coral host's stress response in or out of symbiosis.

Utilization of the Cancer Medications Enquiry Database (CanMED)-National Drug Codes (NDC): Assessment of Systemic Breast Cancer Treatment Patterns

Cancer Medications Enquiry Database (CanMED) is comprised of two interactive, nomenclature-specific databases within the Observational Research in Oncology Toolbox: CanMED-Healthcare Common Procedure Coding System (HCPCS) and CanMED-National Drug Code (NDC), described through this study. CanMED includes medications with a) a US Food and Drug Administration-approved cancer treatment or treatment-related symptom management indication, b) inclusion in treatment guidelines, or c) an orphan drug designation. To demonstrate the joint utility of CanMED, medication codes associated with female breast cancer treatment were identified and utilization patterns were assessed within Surveillance Epidemiology and End Results-Medicare (SEER) data. CanMED-NDC (11_2018 v.1.2.4) includes 6860 NDC codes: chemotherapy (1870), immunotherapy (164), hormone therapy (3074), and ancillary therapy (1752). Treatment patterns among stage I-IIIA (20 701) and stage IIIB-IV (2381) breast cancer patients were accordant with guideline-recommended treatment by stage and molecular subtype. CanMED facilitates identification of medications from observational data (eg, claims and electronic health records), promoting more standardized and efficient treatment-related cancer research.

Development and Utility of the Observational Research in Oncology Toolbox: Cancer Medications Enquiry Database-Healthcare Common Procedure Coding System (HCPCS)

PURPOSE

Health-care claims are of increasing utility as a rich, real-world data resource for conducting treatment-related cancer research. However, multiple dynamic coding nomenclatures exist, leading to study variability. To promote increased standardization and reproducibility, the National Cancer Institute (NCI) developed the Cancer Medications Enquiry Database (CanMED)-Healthcare Common Procedure Coding System (HCPCS) within the Observational Research in Oncology Toolbox.

METHODS

The CanMED-HCPCS includes codes for oncology medications that a) have a US Food and Drug Administration-approved indication for cancer treatment or treatment-related symptom management; b) are present in National Comprehensive Cancer Network guidelines; or c) carry an orphan drug designation for treatment or management of cancer. Included medications and their HCPCS codes were primarily identified based on Center for Medicare and Medicaid Services annual HCPCS Indices (2012-2018). To demonstrate the utility of the CanMED-HCPCS, use of systemic treatment for stage II-IV colorectal cancer patients included in the Surveillance, Epidemiology, and End Results-Medicare data (2007-2013) was assessed.

RESULTS

The CanMED-HCPCS (v2018) includes 332 HCPCS codes for cancer-related medications: chemotherapy (156), immunotherapy (74), hormonal therapy (54), and ancillary therapy (48). Observed treatment trends within the NCI Surveillance, Epidemiology, and End Results-Medicare data were as expected; utilization of each treatment type increased with stage, and immunotherapy was largely confined to use among stage IV patients.

CONCLUSION

The CanMED-HCPCS provides a comprehensive resource that can be used by the research community to facilitate systematic identification of medications within claims or electronic health data using the HCPCS nomenclature and greater reproducibility of cancer surveillance and health services research.

P3: CASE-CONTROL STUDY OF SEXUAL BEHAVIOUR IN HPV-POSITIVE ORAL CAVITY AND OROPHARYNGEAL CANCER

Introduction

HPV infection is recognised as the main aetiological factor responsible for the increased incidence of oropharyngeal squamous cell carcinomas (OPSCC). Currently the epidemiology of oral HPV infection and OPSCC is poorly understood. In this study we aim to define the relationship between sexual behaviours and HPV-positive OPSCC.

Method

We performed a hospital-based, case-control study of 30 patients with HPV-positive and 30 patients with HPV-negative newly diagnosed oral cavity and OPSCC. The participants underwent questionnaire based interviews investigating variables such as age, gender, tobacco use, alcohol intake, and sexual behaviour.

Result

Subjects in the HPV-positive tumour subgroup had significantly less tobacco use then their HPV-negative counterparts (odds ratio, 0.92, 95% CI 0.9-1.17). A history of oral sexual activity was significantly more likely in the HPV-positive tumour subgroup (odds ratio, 5.23, 95% CI, 1.66-16.51), however this association did not remain significant when adjusted for age, gender, smoking and alcohol consumption. Similarly, there was significantly less alcohol consumption overall in the HPV-positive tumour subgroup (odds ratio, 0.107, 95% CI 0.96-1.01), but this association was no longer significant when adjusted for covariables.

Conclusion

Significantly less smoking was prevalent in patients with HPV-positive OPSCC. Although patients with HPV-positive tumours had less alcohol consumption and a stronger history of oral sexual activity overall, greater numbers are required in order to show a significant association. This further supports the known association between HPV-infection and OPSCC and the department of health's decision to commence vaccination of boys before the onset of sexual activity.

Take-home message

HPV-positive oropharyngeal cancer can develop without exposure to established risk factors such as tobacco use or excessive alcohol consumption. This change in pathogenesis should lead a change in how we prevent and manage the disease.

Tracheostomy stomal seeding following oral cavity resection

BACKGROUND

Tracheal stoma recurrence following oral cavity surgery is exceedingly rare. Although several different mechanisms for this have been described, the pathogenesis still remains uncertain.

METHODS

We present the case of a gentleman who presented 6-months following oral cavity SCC resection with a large fungating mass at his previous tracheostomy site, and also review the reported literature on this rare phenomenon.

RESULTS

Four weeks after diagnosis of his recurrence he underwent a total laryngectomy, wide-local skin excision and reconstruction with a pectoralis major pedicled flap. He recovered well initially following his operation, however unfortunately contracted nosocomial SARS-Cov2 and succumbed from respiratory complications during his post-operative recovery.

CONCLUSION

Stomal recurrence after temporary tracheostomy for oral cavity malignancies are very rare. Previously reported management of these can vary from surgical to palliative treatment. Methods to prevent these include delaying tracheostomy until after surgical resection, packing the pharynx during resection and adjuvant radiotherapy.

Targeting Lifestyle Behavior to Improve Brain Health: User-Experiences of an Online Program for Individuals with Subjective Cognitive Decline

BACKGROUND

Online programs targeting lifestyle have the potential to benefit brain health. We aimed to develop such a program for individuals with subjective cognitive decline (SCD). These individuals were reported to be at increased risk for dementia, and report both an intrinsic need for brain health information and motivation to participate in prevention strategies. Co-creation and user-evaluation benefits the adherence to and acceptance of online programs. Previously, we developed a prototype of the online program in co-creation with the users .

OBJECTIVES

We now aimed to evaluate the user-experiences of our online lifestyle program for brain health.

DESIGN

30-day user test; multi-method.

SETTING

Participants were recruited in a memory clinic and (online) research registries in the Netherlands (Alzheimer Center Amsterdam) and Germany (Center for memory disorders, Cologne).

PARTICIPANTS

Individuals with SCD (N=137, 65±9y, 57% female).

MEASUREMENTS

We assessed user-experiences quantitatively with rating daily advices and usefulness, satisfaction and ease of use questionnaires as well as qualitatively using telephone interviews.

RESULTS

Quantitative data showed that daily advices were rated moderately useful (3.5 ±1.5, range 1-5 points). Participants (n=101, 78%) gave moderate ratings on the programs' usability (3.7±1.3, max 7), ease of learning (3.6±1.9) and satisfaction (4.0±1.5), and marginal ratings on the overall usability (63.7±19.0, max 100). Qualitative data collected during telephone interviews showed that participants highly appreciated the content of the program. They elaborated that lower ratings of the program were mainly due to technical issues that hindered a smooth walk through. Participants reported that the program increased awareness of lifestyle factors related to brain health.

CONCLUSIONS

Overall user-experience of the online lifestyle program was moderate to positive. Qualitative data showed that content was appreciated and that flawless, easy access technique is essential. The heterogeneity in ratings of program content and in program use highlights the need for personalization. These findings support the use of online self-applied lifestyle programs when aiming to reach large groups of motivated at-risk individuals for brain health promotion.

Deep-Channel uses deep neural networks to detect single-molecule events from patch-clamp data

Single-molecule research techniques such as patch-clamp electrophysiology deliver unique biological insight by capturing the movement of individual proteins in real time, unobscured by whole-cell ensemble averaging. The critical first step in analysis is event detection, so called "idealisation", where noisy raw data are turned into discrete records of protein movement. To date there have been practical limitations in patch-clamp data idealisation; high quality idealisation is typically laborious and becomes infeasible and subjective with complex biological data containing many distinct native single-ion channel proteins gating simultaneously. Here, we show a deep learning model based on convolutional neural networks and long short-term memory architecture can automatically idealise complex single molecule activity more accurately and faster than traditional methods. There are no parameters to set; baseline, channel amplitude or numbers of channels for example. We believe this approach could revolutionise the unsupervised automatic detection of single-molecule transition events in the future.

A novel form of glycolytic metabolism-dependent cardioprotection revealed by PKCα and β inhibition

KEY POINTS

Acute hyperglycaemia at the time of a heart attack worsens the outcome for the patient. Acute hyperglycaemia is not limited to diabetic patients and can be due to a stress response in non-diabetics. This study suggests that the damaging cardiac effects of hyperglycaemia can be reversed by selective PKC inhibition. If PKCα/β isoforms are inhibited, then high glucose itself becomes protective against ischaemic damage. Selective PKC inhibition may therefore be a useful therapeutic tool to limit the damage that can occur during a heart attack by stress-induced hyperglycaemia.

ABSTRACT

Hyperglycaemia has a powerful association with adverse prognosis for patients with acute coronary syndromes (ACS). Previous work shows that high glucose prevents ischaemic preconditioning and causes electrical and mechanical disruption via protein kinase C α/β (PKCα/β) activation. The present study aimed to: (i) determine whether the adverse clinical association of hyperglycaemia in ACS can be replicated in preclinical cellular models of ACS and (ii) determine the importance of PKCα/β activation to the deleterious effect of glucose. Freshly isolated rat, guinea pig or rabbit cardiomyocytes were exposed to simulated ischaemia after incubation in the presence of normal (5 mm) or high (20 mm) glucose in the absence or presence of small molecule or tat-peptide-linked PKCαβ inhibitors. In each of the four conditions, the following hallmarks of cardioprotection were recorded using electrophysiology or fluorescence imaging: cardiomyocyte contraction and survival, action potential stability and time to failure, intracellular calcium and ATP, mitochondrial depolarization, ischaemia-sensitive leak current, and time to K_ir 6.2 opening. High glucose alone resulted in decreased cardiomyocyte contraction and survival; however, it also imparted cardioprotection in the presence of PKCα/β inhibitors. This cardioprotective phenotype displayed improvements in all of the measured parameters and decreased myocardium damage during whole heart coronary ligation experiments. High glucose is deleterious to cellular and whole-heart models of simulated ischaemia, in keeping with the clinical association of hyperglycaemia with an adverse outcome in ACS. PKCαβ inhibition revealed high glucose to show a cardioprotective phenotype in this setting. The results of the present study suggest the potential for the therapeutic application of PKCαβ inhibition in ACS associated with hyperglycaemia.

Abstract 2924: Evaluation of the pan-FGFR inhibitor AZD4547 with radiation in non-small cell lung cancer

Objective: The fibroblast growth factor receptors (FGFR) are commonly altered in non-small cell lung cancer (NSCLC), including high level of amplification of FGFR1 in lung squamous cell carcinoma. FGFR signaling may play a role in the response to radiation. We investigated the radiosensitizing effects of the selective tyrosine kinase inhibitor AZD4547 in a NSCLC model using cell lines and tumor xenografts.

Methods: A panel of six NSCLC cell lines were screened for FGFR1/2 DNA amplification, RNA expression, and protein expression. All cells were assessed for in vitro response to AZD4547. Immunoblots were used to examine the effect of AZD4547 on downstream signaling proteins. Apoptosis was measured by Annexin V staining and autophagy with acridine orange assay. Radiation clonogenic survival assays and xenograft growth delays experiments were performed to investigate radiosensitization. In vivo mechanistic studies were conducted using immunohistochemistry.

Results: Cell lines demonstrated varying degree of FGFR1/2 RNA and protein expression. In sensitive cell lines, AZD4547 inhibited p-MAPK in a time dependent manner. In vitro clonogenic survival assays showed robust radiosensitivity with AZD4547 in three out of six NSCLC cell lines. All three cell lines overexpressed FGFR1 and two of the cells had high FGFR1 copy number. There was no radiosensitization seen in an immortalized normal human bronchial epithelial cell line. A significant increase in autophagy and apoptosis was observed with combined radiation and AZD4547. Significant tumor growth delay was observed with the administration of radiation and AZD4547 compared to radiation or drug alone in two NSCLC xenograft tumor models. IHC analysis revealed modulation of FGFR-downstream signaling (p-Erk and p-S6) and proliferative (Ki67) and apoptotic markers (Cleaved Caspace 3).

Conclusion: These findings suggest that AZD4547 can augment the response of radiation in NSCLC model systems. FGFR1 and FGFR2 expression may be a potential targets for radiosensitization in NSCLC. Additional studies are underway to understand the mechanism of radiosensitization.

Citation Format: Margot Miller, Michael Fisher, Gopika Senthilkumar, Saakshi Kaushik, Lindsey Able, Sean Brennan, Gopal Iyer, Randall Kimple, Andrew M. Baschnagel. Evaluation of the pan-FGFR inhibitor AZD4547 with radiation in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2924.

Abstract 2929: Radiosensitization of head and neck cancer by FGFR inhibition

Objective:

Fibroblast growth factor receptors are frequently amplified or overexpressed in head and neck squamous cell carcinomas (HNSCC). We assessed the potential of a selective FGFR-kinase inhibitor, AZD4547, to act as a radiosensitizer in head and neck cancer cell lines and xenografts.

Methods:

A panel of head and neck cancer (n=10) and normal oral mucosa (HTE) cell lines were screened for FGFR1, 2, and 3 gene copy number, RNA expression, and protein. Sensitivity to the FGFR inhibitor AZD4547, alone or in combination with radiation, was assessed using proliferation and clonogenic survival assays. Putative mechanisms of radiosensitization were investigated by immunoblot and by assessing for DNA repair capacity, cell cycle effects, apoptosis, senescence, and autophagy. Tumor response of cell line xenografts and patient derived xenografts was assessed in vivo.

Results:

Cells demonstrated varying responses to FGFR inhibition but this did not correlate with FGFR gene copy number, mRNA expression, or protein expression. Three cell lines which responded to AZD4547 alone (CCL30, Tu-138, and SCC6) were selected for further investigation. TU-138 and CCL30 featured high FGFR expression and were radiosensitized by AZD4547 in vitro. SCC6 was not. Cell lines which were insensitive to FGFR inhibition (including HTE) did not demonstrate radiosensitization by AZD4547. In the sensitive cell lines, enhanced p-MAPK inhibition was seen in a time-dependent manner following drug treatment. When added to radiation, AZD4547 resulted in increased apoptosis, autophagy, and senescence but did not alter the kinetics of DNA repair as assessed by resolution of gH2AX foci. No difference in the cell cycle distribution for irradiated cells treated with or without the addition of AZD4547 was seen. Treatment of two in vivo tumor xenografts with AZD4547 and radiation showed significant delay in tumor growth compared to treatment with radiation or drug alone.

Conclusion:

Our findings indicate that AZD4547 can augment the response of FGFR expressing HNSCC to radiation both in vitro and in vivo. Improved approaches to identify tumors most likely to benefit from FGFR inhibition could enable the selection of patients for combination therapy and has the potential to improve outcomes in these difficult to treat cancers.

Citation Format: Gopika SenthilKumar, Margot Miller, Michael Fisher, Sean Brennan, Saakshi Kaushik, Lindsey Able, Paul M. Harari, Gopal Iyer, Randall J. Kimple, Andrew M. Baschnagel. Radiosensitization of head and neck cancer by FGFR inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2929.

Small-Molecule G Protein-Coupled Receptor Kinase Inhibitors Attenuate G Protein-Coupled Receptor Kinase 2-Mediated Desensitization of Vasoconstrictor-Induced Arterial Contractions

Vasoconstrictor-driven G protein-coupled receptor (GPCR)/phospholipase C (PLC) signaling increases intracellular Ca²⁺ concentration to mediate arterial contraction. To counteract vasoconstrictor-induced contraction, GPCR/PLC signaling can be desensitized by G protein-coupled receptor kinases (GRKs), with GRK2 playing a predominant role in isolated arterial smooth muscle cells. In this study, we use an array of GRK2 inhibitors to assess their effects on the desensitization of UTP and angiotensin II (AngII)-mediated arterial contractions. The effects of GRK2 inhibitors on the desensitization of UTP- or AngII-stimulated mesenteric third-order arterial contractions, and PLC activity in isolated mesenteric smooth muscle cells (MSMC), were determined using wire myography and Ca²⁺ imaging, respectively. Applying a stimulation protocol to cause receptor desensitization resulted in reductions in UTP- and AngII-stimulated arterial contractions. Preincubation with the GRK2 inhibitor paroxetine almost completely prevented desensitization of UTP- and attenuated desensitization of AngII-stimulated arterial contractions. In contrast, fluoxetine was ineffective. Preincubation with alternative GRK2 inhibitors (Takeda compound 101 or CCG224063) also attenuated the desensitization of UTP-mediated arterial contractile responses. In isolated MSMC, paroxetine, Takeda compound 101, and CCG224063 also attenuated the desensitization of UTP- and AngII-stimulated increases in Ca²⁺, whereas fluoxetine did not. In human uterine smooth muscle cells, paroxetine reversed GRK2-mediated histamine H₁ receptor desensitization, but not GRK6-mediated oxytocin receptor desensitization. Utilizing various small-molecule GRK2 inhibitors, we confirm that GRK2 plays a central role in regulating vasoconstrictor-mediated arterial tone, highlighting a potentially novel strategy for blood pressure regulation through targeting GRK2 function.

Abstract 3946: Androgen receptor drives differential gene expression in KRAS-mediated non-small cell lung cancer

The Cancer Genome Atlas (TCGA) has identified alterations such as amplification, deletion, or mutation of androgen receptor (AR) in about 5% of human lung squamous cell carcinoma and adenocarcinoma. The expression of AR in human lung appears to play a crucial role in lung development and type II pneumocytes (PTII) maturation, but unlike in prostate cancer, the role of AR is not well known in non-small cell lung cancer (NSCLC). In our study, we demonstrated AR in NSCLC cell lines translocated into the nucleus over time when stimulated with synthetic androgen R1881, while addition of enzalutamide (MDV3100) or AR siRNA reduced AR nuclear localization. Using an NSCLC human tissue microarray also revealed that 10 out of 88 patients (11%) have positive AR immunohistochemical staining. Preliminary data from clonogenic assay indicated that enzalutamide might have radiosensitizing effect on certain NSCLC cells at 2 Gy, further suggesting the involvement of AR in lung cancer and its potential therapeutic value as a target. With the induction of R1881 for 30 minutes to 24 hours, certain NSCLC cells display decreased AR mRNA (0.5-0.8 fold), while others show modest increase (up to 1.5 fold), suggesting that AR regulation in these cells might be different due to their mutational landscapes. We then used predesigned 384 well panels from Bio-Rad to survey the effects of R1881, enzalutamide, and AR siRNA on mRNA expression levels of selected NSCLC cells. Distinct expression profiles were observed between cells that have wild-type and mutated KRAS. Taken together, these findings suggest that the AR signaling could be different based on KRAS mutational profiles of NSCLCs, and further work is required to reveal the underlying mechanism. Chromatin immunoprecipitation (ChIP) assay and RNA sequencing will be utilized to investigate AR interactions with androgen response elements and differential expressions in KRAS-driven NSCLC cells, respectively.

Citation Format: Albert Roy Wang, Hope Beyer, Sean Brennan, Shannon Stiles, Dylan Wiese, Darya Buehler, Anwaar Saeed, Andrew M. Baschnagel, Gopal Iyer. Androgen receptor drives differential gene expression in KRAS-mediated non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3946.

A research and evaluation capacity building model in Western Australia

Evaluation of public health programs, services and policies is increasingly required to demonstrate effectiveness. Funding constraints necessitate that existing programs, services and policies be evaluated and their findings disseminated. Evidence-informed practice and policy is also desirable to maximise investments in public health. Partnerships between public health researchers, service providers and policymakers can help address evaluation knowledge and skills gaps. The Western Australian Sexual Health and Blood-borne Virus Applied Research and Evaluation Network (SiREN) aims to build research and evaluation capacity in the sexual health and blood-borne virus sector in Western Australia (WA). Partners' perspectives of the SiREN model after 2 years were explored. Qualitative written responses from service providers, policymakers and researchers about the SiREN model were analysed thematically. Service providers reported that participation in SiREN prompted them to consider evaluation earlier in the planning process and increased their appreciation of the value of evaluation. Policymakers noted benefits of the model in generating local evidence and highlighting local issues of importance for consideration at a national level. Researchers identified challenges communicating the services available through SiREN and the time investment needed to develop effective collaborative partnerships. Stronger engagement between public health researchers, service providers and policymakers through collaborative partnerships has the potential to improve evidence generation and evidence translation. These outcomes require long-term funding and commitment from all partners to develop and maintain partnerships. Ongoing monitoring and evaluation can ensure the partnership remains responsive to the needs of key stakeholders. The findings are applicable to many sectors.

Abstract 827: Statistical analyses of stable housekeeping gene expression in cancer post-irradiation

Ionizing radiation (IR) can induce DNA damage in human cells and result in changes in gene expression. The changes could also include some of the commonly used housekeeping genes (HKG), and thus making them unstable over the time period after being exposed to radiation. Normalization of housekeeping genes is critical for understanding gene expression post-irradiation. Toward the validation of stable HKGs, cancer cell lines from head and neck, non-small cell lung and pancreas were irradiated to 2, 4 and 6 Gy IR doses. Statistical analysis of RNA expression of fourteen HKGs measured at 5 min to 48hrs post-irradiation reveal tradition HKGs such as beta-actin (ACTB) and glucose-6-phosphate-dehydrogenase (G6PD) to be unstable, while TATA-Box Binding Protein (TBP) and Importin 8 (IPO8) was identified as stable HKGs in non-small lung and pancreas cell across all IR doses and time. Interestingly in head and neck cancer, TBP is also found stable across all IR doses and time. The statistical framework used for identification and validation of HKGs can serve as a reliable metric for quantifying gene expression post-irradiation.

Citation Format: Albert R. Wang, Gopal Iyer, Sean Brennan, Shay Bourgeois, Eric Armstrong, Pari Shah, Paul M. Harari. Statistical analyses of stable housekeeping gene expression in cancer post-irradiation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 827. doi:10.1158/1538-7445.AM2017-827

Abstract 4121: Androgen receptor as a potential target in non-small cell lung cancer

The cancer genome atlas (TCGA) has identified androgen receptor (AR) to be mutated, deleted and amplified across human lung squamous cell carcinoma and adenocarcinoma. Expression of AR is critical for early lung development. However, the intriguing expression of AR in non-small cell lung cancer (NSCLC) opens up an alternative treatment paradigm in the event of onset of clinical resistance to lung cancer drugs. To investigate this potential, a) 10 NSCLC cell lines and 3 control prostate cancer cell lines were stimulated with synthetic AR agonist, R1881 at 24, 48 and 72 hours. 0.5-4-fold RNA and protein expression was found across these lung cancer cell lines when compared to unstimulated cells. b) droplet digital PCR revealed varying copies of AR DNA when benchmarked to prostate AR. c) cell proliferation assays of these cell lines with enzalutamide (MVD3100) treatment resulted in 50-65% cell survival at concentrations ranging from 10 - 25 µM. d) Immunohistochemical staining of AR in a NSCLC human tissue microarray (TMA) revealed 10 out of 88 patients (11%) to have AR positive staining in their tumor. This included 6 adenocarcinomas and 2 squamous cell carcinomas. 8 patients had focal while 2 had diffuse staining. Validation of the TMA performed with whole mount slides confirmed diffuse staining in these 11 samples. Taken together, these findings suggest AR is a potential therapeutic target in NSCLC and further work is underway to test these observations in drug resistant lung cancer cell lines and pre-clinical mouse models.

Citation Format: Sean Brennan, Albert R. Wang, Hope Beyer, Dylan Wiese, Darya Buehler, Anwaar Saeed, Andrew M. Baschnagel, Gopal Iyer. Androgen receptor as a potential target in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4121. doi:10.1158/1538-7445.AM2017-4121

Determination of copper nanoparticle size distributions with total reflection X-ray fluorescence spectroscopy

Total reflection X-ray fluorescence (TXRF) analysis is extensively used by the semiconductor industry for measuring trace metal contamination on silicon surfaces. In addition to determining the quantity of impurities on a surface, TXRF can reveal information about the vertical distribution of contaminants by measuring the fluorescence signal as a function of the angle of incidence. In this study, two samples were intentionally contaminated with copper in non-deoxygenated and deoxygenated ultrapure water (UPW) resulting in impurity profiles that were either atomically dispersed in a thin film or particle-like, respectively. The concentration profile of the samples immersed into deoxygenated UPW was calculated using a theoretical concentration profile representative of particles, yielding a mean particle height of 16.1 nm. However, the resulting theoretical profile suggested that a distribution of particle heights exists on the surface. The fit of the angular distribution data was further refined by minimizing the residual error of a least-squares fit employing a model with a Gaussian distribution of particle heights about the mean height. The presence of a height distribution was also confirmed with atomic force microscopy measurements.

Population-based cohort study of variation in the use of emergency cholecystectomy for benign gallbladder diseases

Background

The aims of this prospective population-based cohort study were to identify the patient and hospital characteristics associated with emergency cholecystectomy, and the influences of these in determining variations between hospitals.

Methods

Data were collected for consecutive patients undergoing cholecystectomy in acute UK and Irish hospitals between 1 March and 1 May 2014. Potential explanatory variables influencing the performance of emergency cholecystectomy were analysed by means of multilevel, multivariable logistic regression modelling using a two-level hierarchical structure with patients (level 1) nested within hospitals (level 2).

Results

Data were collected on 4744 cholecystectomies from 165 hospitals. Increasing age, lower ASA fitness grade, biliary colic, the need for further imaging (magnetic retrograde cholangiopancreatography), endoscopic interventions (endoscopic retrograde cholangiopancreatography) and admission to a non-biliary centre significantly reduced the likelihood of an emergency cholecystectomy being performed. The multilevel model was used to calculate the probability of receiving an emergency cholecystectomy for a woman aged 40 years or over with an ASA grade of I or II and a BMI of at least 25·0 kg/m2, who presented with acute cholecystitis with an ultrasound scan showing a thick-walled gallbladder and a normal common bile duct. The mean predicted probability of receiving an emergency cholecystectomy was 0·52 (95 per cent c.i. 0·45 to 0·57). The predicted probabilities ranged from 0·02 to 0·95 across the 165 hospitals, demonstrating significant variation between hospitals.

Conclusion

Patients with similar characteristics presenting to different hospitals with acute gallbladder pathology do not receive comparable care.

Anodal transcranial direct current stimulation of the left dorsolateral prefrontal cortex enhances emotion recognition in depressed patients and controls

INTRODUCTION

Transcranial direct current stimulation (tDCS) can enhance a range of neuropsychological functions but its efficacy in addressing clinically significant emotion recognition deficits associated with depression is largely untested.

METHOD

A randomized crossover placebo controlled study was used to investigate the effects of tDCS over the left dorsolateral prefrontal cortex (L-DLPFC) on a range of neuropsychological variables associated with depression as well as neural activity in the associated brain region. A series of computerized tests was administered to clinical (n = 17) and control groups (n = 20) during sham and anodal (1.5 mA) stimulation.

RESULTS

Anodal tDCS led to a significant main effect for overall emotion recognition (p = .02), with a significant improvement in the control group (p = .04). Recognition of disgust was significantly greater in the clinical group (p = .01). Recognition of anger was significantly improved for the clinical group (p = .04) during anodal stimulation. Differences between groups for each of the six emotions at varying levels of expression found that at 40% during anodal stimulation, happy recognition significantly improved for the clinical group (p = .01). Anger recognition at 80% during anodal stimulation significantly improved for the clinical group (p = .02). These improvements were observed in the absence of any change in psychomotor speed or trail making ability during anodal stimulation. Working memory significantly improved during anodal stimulation for the clinical group but not for controls (p = .03).

CONCLUSIONS

The tentative findings of this study indicate that tDCS can have a neuromodulatory effect on a range of neuropsychological variables. However, it is clear that there was a wide variation in responses to tDCS and that individual difference and different approaches to testing and stimulation have a significant impact on final outcomes. Nonetheless, tDCS remains a promising tool for future neuropsychological research.

The Toxicity of Commonly Used Antiseptics on Fibroblasts in Tissue Culture

We have allowed the liberal use of antiseptics for wound care to become an established practice with little consideration of any toxicity on exposed healing tissues. The care of open wounds and chronic ulcers is largely delegated to nursing staff with little help or advice from their medical colleagues. Alexander Fleming felt that antiseptics would only be of benefit in septic wounds if they stimulated or conserved natural defence mechanisms! He also regarded the assessment of tissue toxicity as being more important than any antimicrobial effect but there has been little research into this field.

Distinct and complementary roles for α and β isoenzymes of PKC in mediating vasoconstrictor responses to acutely elevated glucose

BACKGROUND AND PURPOSE

We investigated the hypothesis that elevated glucose increases contractile responses in vascular smooth muscle and that this enhanced constriction occurs due to the glucose-induced PKC-dependent inhibition of voltage-gated potassium channels.

EXPERIMENTAL APPROACH

Patch-clamp electrophysiology in rat isolated mesenteric arterial myocytes was performed to investigate the glucose-induced inhibition of voltage-gated potassium (Kv ) current. To determine the effects of glucose in whole vessel, wire myography was performed in rat mesenteric, porcine coronary and human internal mammary arteries.

KEY RESULTS

Glucose-induced inhibition of Kv was PKC-dependent and could be pharmacologically dissected using PKC isoenzyme-specific inhibitors to reveal a PKCβ-dependent component of Kv inhibition dominating between 0 and 10 mM glucose with an additional PKCα-dependent component becoming evident at concentrations greater than 10 mM. These findings were supported using wire myography in all artery types used, where contractile responses to vessel depolarization and vasoconstrictors were enhanced by increasing bathing glucose concentration, again with evidence for distinct and complementary PKCα/PKCβ-mediated components.

CONCLUSIONS AND IMPLICATIONS

Our results provide compelling evidence that glucose-induced PKCα/PKCβ-mediated inhibition of Kv current in vascular smooth muscle causes an enhanced constrictor response. Inhibition of Kv current causes a significant depolarization of vascular myocytes leading to marked vasoconstriction. The PKC dependence of this enhanced constrictor response may present a potential therapeutic target for improving microvascular perfusion following percutaneous coronary intervention after myocardial infarction in hyperglycaemic patients.