Year: 2015

Development of novel indolmycin derivatives for the treatment of MRSA

Since the discovery of antibiotics over 80 years ago, bacterial infections have been relatively straightforward to treat. However, the improper use of antibiotics has caused bacteria to develop antibiotic resistance, posing a serious global threat to preventing and treating common bacterial infections.

This project seeks to combat multi-drug resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) by improving on an antimicrobial compound that naturally occurs in the environment. Indolmycin is naturally produced by Streptomyces griseus and is active against multi-drug resistant MRSA strains.

We aim to develop forms of indolmycin that are more potent against MRSA by feeding Streptomyces griseus with variant amino acids. In addition, we will perform structure-based studies to elucidate the molecular mechanism of anti-MRSA activity in indolmycin. This will allow for rational design of more effective forms of indolmycin.

Ultimately, this research could give rise to novel antibiotics to treat infections such as MRSA that are developing resistance to our current toolkit.

Altered glutamate dynamics in a mouse model of Alzheimer’s disease: Novel early biomarkers with therapeutic potential

Michael Smith Foundation for Health Research/The Pacific Alzheimer Research Foundation Post-Doctoral Fellowship Award

 

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder. With no cure available, it imposes a major burden on society. In AD, a protein called amyloid beta accumulates into plaques in the brain. This event is an early and predictive marker for AD and can be detected up to 20 years before clinical symptoms arise.

 

We are exploring the dysfunction and hyperactivity of various cell types in the presence of amyloid plaques. We will investigate the possible role of altered glutamate dynamics in mouse models of AD. Fluorescent labelling will shed light on changes in glutamate signalling in awake and behaving AD mice. We will also test whether Ceftriaxone can restore normal glutamate dynamics in these mice.

 

Ultimately, our work with AD mouse models and novel glutamate imaging could shed light on possible drug targets and enable early intervention for people with Alzheimer’s disease.

End of Award Update

Source: CLEAR Foundation

 

What did we learn?

During our study it became clear that amyloid deposits have a drastic impact on glutamate signaling. This early cellular signaling deficit was only visible using in vivo 2-Photon imaging and a region-specific analysis of real time glutamate transients in direct proximity to amyloid plaques. We found areas of chronically high glutamate levels directly surrounding amyloid plaques and adjacent areas in which glutamate signaling was impaired. In larger scale wide-field real-time imaging experiments this effect was lost, indicating the importance of region-specific effects on cellular function in the early stages of the disease. Moreover, we used luminescent conjucated oligothiophens (provided by Dr. Peter Nilson, Linköping University) to visualize prefibrillary forms of amyloid. We found a direct overlap of these prefibrillary forms of amyloid surrounding the dense core plaque and a decrease in astrocytic GLT-1 transporter. We hypothesized that this decrease in GLT-1 is responsible for the observed glutamate dysfunction that was found in our experiments using stimulation experiments in awake and anesthetized animals. We thus used Ceftriaxone to restore GLT-1 expression in our mouse model of AD. We provided longitudinal imaging data of glutamate transients before and after Ceftriaxone treatment and could show that this partially restores glutamate signaling.

 

Why is this knowledge important?

As prefibrillary species are present in the brain before dense core plaques are formed it is important to further our understanding of their impact on cellular function. Moreover, it is essential to develop strategies that aim at the earlies stage that amyloids have on cellular function as these can be treated. Once neurons and other cells undergo cell death, strategies of recovery are much harder to implement. Our results provided a new therapeutical target that not only treats the disease on a symptomatic level but in an amyloid centric way that prevents/delays cellular dysfunction at an early stage in the disease.

 

What are the next steps?

We are currently expanding our research to investigate the impact of prefibrillary amyloid species on vessel function to search for more potential therapeutic targets.

 

Publications

Characterizing Arm Recovery in People with Severe Stroke (CARPSS)

In Canada, there are over 50,000 new strokes reported every year. The prevalence and severity of subsequent upper limb disability is increasing and the prospect of complete recovery is poor. Stroke survivors who lack early indicators of a good prognosis, such as movement at the shoulder or wrist, are considered unlikely to regain much arm function through rehabilitation. However, a growing body of evidence suggests that untapped recovery potential may be better assessed from brain scans.

This project will create a data set that sheds light on 'who recovers' and 'who does not recover' by examining how the severely damaged brain changes over the first year post stroke. A series of brain scans and clinical tests of motor recovery will be performed for fifty adults with severe upper limb impairment after their first stroke. Their upper limb use during training and real world settings will also be documented.

This research will support the development of personalized training approaches that maximize functional recovery following stroke.

The role and regulation of pannexin ion channels during cytotoxic edema

A primary and often fatal consequence of stroke, traumatic brain injury, and other brain insults is edema: an increase in brain tissue water content. Cytotoxic edema is a component of this process and occurs when excess ions and water enter across the neuronal plasma membrane -the semi-permeable barrier separating the intra- and extracellular space. This increase in cell volume causes membrane swelling and ultimately results in cell death.    

Presently, the cascade of events by which neuronal swelling triggers cell death remains obscure. Preliminary evidence from Dr. Brian MacVicar's lab (the host) indicates that swelling triggers cell death by activating pannexins- a class of large transmembrane ion channels. Following activation, pannexins form large pores in the membrane and allow ions and small molecules to diffuse between the intra- and extracellular compartments. Consequently, pannexins can initiate cell death by collapsing the transmembrane electrochemical gradient and/or promoting the loss of essential cellular components. The precise mechanism by which swelling triggers the opening of pannexins is unknown. Interestingly, these ion channels can be mechanically activated by membrane stretch. Moreover, membrane stretch also leads to the production of reactive oxygen species (ROS)-a group of harmful chemical agents that can directly activate pannexins.    

For the present proposal, we will test the hypothesis that pannexin activation is a crucial step underlying cell death following cytotoxic edema. Furthermore, we hypothesize that pannexins are activated by neuronal swelling through direct mechanical stimulation and/or the production of ROS.   

These hypotheses will be tested in acutely prepared rat brain slices using advanced microscopy/imaging and electrophysiology techniques. As there are few effective treatments for edema, this research could reveal new avenues for therapeutic intervention following a variety of brain insults. Considering the implications of this project for basic biomedical and clinical research, it will be essential to diffuse and disseminate our knowledge to a variety of communities. This will be done largely through symposiums/presentations at the Society for Neuroscience as well as publication in peer-reviewed scientific journals.

A primary and often fatal consequence of brain insults such as stroke and traumatic injury is edema: an increase in brain tissue water content. Cytotoxic edema is a component of this process, which occurs at the level of individual brain cells, or neurons. The cells swell up as excess ions and water enter, causing them to die. This project will build on earlier work carried out under the project supervisor, which suggests that cytotoxic edema is caused by the action of pannexins.

Pannexins are activated through unknown mechanisms when the cell membrane is caused to stretch, either chemically through the production of reactive oxygen species or mechanically. Following activation, pannexins form large pores in the cell membrane that allow ions and small molecules to pass through. They are believed to cause cell death by collapsing the transmembrane electrochemical gradient and/or by promoting the loss of essential cellular components.

We will study tissue samples using advanced imaging and electrophysiology techniques to test the hypotheses that:

  1. Pannexin activation is a crucial step underlying neuronal cell death in the brain following cytotoxic edema
  2. Pannexins are activated by neuronal swelling through direct mechanical stimulation and/or the production of reactive oxygen species

New lines of research for therapies for damage to the brain are greatly needed and some could arise from this work.

Understanding the role of information in vaccine hesitant parents’ decision-making

Vaccination has been proven to be an effective tool to combat the spread of many communicable diseases. However, recent outbreaks of vaccine-preventable diseases such as measles have heightened concern regarding parents who are vaccine hesitant (i.e. who exhibit delayed acceptance or refusal of some or all vaccines).

Understanding what types of information most influence parents is key to producing effective public health messages that will improve vaccination rates.

Working in collaboration with the Canadian Immunization Research Network (CIRN), this project will examine the relationships among health information, social context, and parental decision-making around routine early childhood vaccinations.

To understand how information interventions interact with social context to influence parental decisions about routine childhood vaccinations, we will conduct:

  1. critical discourse analysis of vaccine discussions on social media
  2. a study of vaccine-hesitant new parents, following their information use and vaccination decisions over the course of a year
  3. a population survey module on health information seeking and use

This work will complement studies by CIRN and contribute to CIRN recommendations for Canadian immunization policy and practice.

Alteration of intestinal microbiota composition and function by co-trimoxazole use and the effect of these changes on growth in HIV-infected children

Malnutrition in early life underlies almost half of all child deaths globally and has long-term negative effects on education and productivity. HIV infection further compounds these effects in sub-Saharan Africa. The World Health Organization (WHO) recommends daily use of the antibiotic co-trimoxazole (CTX) to prevent infections in HIV-infected children. In addition to reducing deaths from infections, CTX also improves growth, possibly by changing the population of "good" microbes in the intestines.

But using antibiotics on a daily basis risks emergence of antibiotic resistant microbes, which could cause disease.

This project will test the hypotheses that daily CTX use in HIV-infected children causes the population of the microbes in their intestines to show:

  1. An increase in the number of antibiotic resistance genes
  2. An increase in the number of genes that encode proteins involved in nutrient harvesting (e.g. carbohydrate digestion)
  3. A decrease in genes involved in virulence
  4. That these changes drive the effect of CTX on growth

We will analyze child growth measurements and clinical data and will characterize genetic changes to the microbiota in stool specimens using DNA sequencing methods. Data and samples were collected through ARROW, a randomized trial designed to study the impact of CTX use on a number of health outcomes in HIV-infected children in Zimbabwe.

Our goal is to understand how daily use of CTX impacts child health in a wider context and to inform WHO recommendations on CTX use in HIV-infected children.

Supporting women’s sexual and reproductive health and rights through Treatment as Prevention: Investigating the impact of structural and interpersonal violence on HIV and reproductive health inequities among women living with HIV in British Columbia

BC's ambitious "90-90-90" target for 2020 aims to ensure that: 1) 90 percent of people living with HIV/AIDS are aware of their status; 2) 90 percent of those diagnosed receive sustained treatment; and 3) 90 percent of those being treated achieve viral suppression. Access and uptake from all affected groups in BC would be needed to achieve this. This work aims to identify and study barriers to HIV testing and treatment and reproductive health services (e.g. cervical screening, mammograms, fertility and pregnancy services) among marginalized women living with HIV/AIDS (WLWHA) in BC.

Specific areas of study will include:

  • Investigating the impact on disclosure of HIV status to health care providers and intimate partners of social factors such as:
    • criminalization of drug use and sex work
    • gender-based violence
  • Investigating the spatial distribution and accessibility of sexual and reproductive health services and their impact on reproductive health outcomes (e.g. contraceptive usage, cervical screening, unintended pregnancy)
  • Exploring challenges faced by WLWHA with families, including how caregiving demands and gender-based violence affect treatment access and compliance.

The intended outcome of the work is to recommend improved service delivery methods for HIV testing, treatment and reproductive health care with an ultimate goal of informing policies and programming.

The mechanism and significance of the synaptogenic activity of amyloid precursor protein

Michael Smith Foundation for Health Research/The Pacific Alzheimer Research Foundation Post-Doctoral Fellowship Award

Amyloid Precursor Protein (APP) is a cell surface protein that has been mostly studied in the context of Alzheimer’s disease. Much about its normal function remains unknown. APP can cause connections to form between brain cells by an unknown mechanism. We believe this happens through an interaction with synaptic organizing proteins (organizers).

This project will investigate the possibility that APP forms synapses by interacting with major organizers in the brain, namely neurexins and receptor protein tyrosine phosphatases (RPTPs).

To test this, we will use a combination of cell cultures and mouse models. We will test whether APP binds to neurexins and RPTPs and whether binding to these organizers is required for the connection-forming activity of APP. We will also compare brain cell connections in normal mice to those in mice that express an altered form of APP that cannot bind to organizers.

This study may shed light on the function of APP through detailing how it can help form connections between brain cells. If defects in connections between brain cells contribute to neurodegeneration in Alzheimer’s disease, these results could shed light on the mechanisms behind that as well.

Etiology and progression of amyotrophic lateral sclerosis: an epidemiological analysis of environmental risk factors

Amyotrophic lateral sclerosis (ALS) is a devastating disease with fatal outcomes usually within a few years following diagnosis. The progressive degeneration of the nerve cells responsible for muscle movement leads to muscle wasting and paralysis, and eventually restricts breathing. The cause of ALS is unknown and probably includes a number of external factors.

There is a relative lack of very large-scale studies with data on potential risk factors collected before ALS occurs. This project aims to assess data from the entire population of Canada to examine the effect of external factors such as military service, trauma, and medication use on the risk of:

  1. developing ALS
  2. progression of ALS

Ultimately, this research could aid in designing effective disease prevention efforts and treatment strategies.

Continuing Health Impact Assessment (CHIA) of the computer-based Drug and Alcohol Training Assessment in Kenya (eDATA K)

Tobacco, alcohol and other substance use disorders (SUD) are among the most important risk factors for the global burden of disease, with a 38 percent increase in global burden of the disease from substance use in the 20 years between 1990 and 2010, mainly driven by increased drug use (57 percent) and alcohol use (32 percent). The tobacco consumption is also worrisome considering the highest incidence of smoking is among men in low and middle income countries (LMIC), and that in the poorest LMIC households, 10 percent of the total income is spent on tobacco, to the detriment of consumption of healthy food and other essential elements for the health of the whole family.

Clinical prevention and care for these disorders are lacking in LMIC. A project funded by Grand Challenges Canada and run by NextGenU.org and the Africa Mental Health Foundation seeks to address that gap through:

  1. Piloting online training in SUD intervention for health care workers in rural and urban areas of Kenya
  2. Conducting randomized control trials (RCT) of the impact of alcohol brief intervention
  3. Determining the feasibility of sustaining the delivery of the interventions post-randomized control trials

The studies are ongoing, with screening data collected on more than 22,000 adults, enabling recruitment of 1,200 patients from October 2014 to February 2015 in 10 facilities from three counties. The clinical courses to address substance use disorders, and other NextGenU courses, are being used in 134 countries.

The screening included SUD, BMI and physical activity level (to mask the purpose of the trials and to decrease barriers from stigma).

Preliminary analysis shows that the outcomes include alcohol use reduction for the patients, and decrease in stigma from healthcare worker, as well as feasibility of sustaining the intervention post RCT.

This project will analyze the data, including the impact on quality of life, self-stigma, depression, risky sexual practices, general health and mental health status, and other substance use consumption. It will also perform knowledge translation of the clinical impact, and continue to carry out the feasibility assessment of sustaining the interventions.