A system to deliver drugs to individual cells

October 6, 2014

A system to package and deliver drugs to each cell of your body, depending on its needs, has been developed at IISc. “Nanocapsules” made from a special type of material can now deliver drugs right inside cancer affected cells in the body.

“Drug delivery systems” are mechanisms that can be programmed to release drug molecules at targeted cells in the body, using physiological cues present in the body itself. The major hurdle has been that these local cues are not consistent between cells; one needs systems that respond to multiple such cues. Prof. Ashok M Raichur and his team of scientists at the Indian Institute of Science, Bangalore, have demonstrated one of the very few systems that can respond to multiple cues.

There are three ideal characteristics that a drug delivery system should have: (1) the entire drug molecule should be encapsulated, which would prevent its premature release or degradation (2) it should carry the drug safely — and specifically — to the target site and (3) at the target site, it should release the drug molecules using the local physiological cues available.

Hollow nanocapsules were fabricated from special materials called biopolymers, which are materials that do not react with body tissues. These nanocapsules contain components that can respond to local cues integrated in the walls. To avoid premature release of the drug, the walls are crosslinked; this sort of architecture gives scope to load large amounts of drugs into the capsule. The wall structure also makes it possible for a small amount of local cues, like enzymes, to trigger the release of a large number of drug molecules.

The Food and Drug Administration(FDA) approved drug, polypeptide protamine (PRM), used to treat heparin induced toxicity, is one of the stimuli responsive components which is identified and actively cleaved into smaller fragments by trypsin like enzymes. The second component, chondroitin sulphate is susceptible to cleavage by enzyme hyaluronidase and has been used in the treatment of arthritis.

The Layer by Layer (LbL) assembly method used for fabrication of nanocapsules is carried under highly controlled mild conditions and thereby capable of incorporating the sensitive components (biopolymers) used here. It has the capacity to take up an array of materials ranging from small proteins to inorganic molecules. The nanocapsule surface was combined with a molecule used to identify cancer cells, folic acid (Vitamin B9, as we know it).

The drug delivery system was demonstrated using a population of cells in the lab – something called a “cell line”.

The paper appeared in the international journal RSC Advances on 17th September. http://pubs.rsc.org/en/content/articlelanding/2014/ra/c4ra07815b#!divAbs…

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Decoding transmembrane communication in living cells

April 24th, 2015

Living cells aren’t self-sufficient; they need to interact with their environment in order to survive. But these interactions are extensively controlled by the barrier called the cell membrane, a dynamic entity made up of lipids and proteins. Molecules are constantly passing in and out of the cell through the semi-permeable cell membrane, their movement often orchestrated by different forces and membrane components. This was the level of understanding of this barrier’s structure and function, posited by the ‘fluid mosaic’ model developed by Singer and Nicholson in 1972. Little was known then about minute details of the driving forces at the nano scale.

Until now, the nitty-gritty of how information traverses the membrane had been left to cell biologists’ countless hypotheses. Fast-forward to the 21st century, some of those assumptions have been put to rest by a recent study at NCBS. An interdisciplinary team has used living cells, synthetic lipid analogs and molecular dynamic simulations to understand transbilayer communication between molecules on either side of the bilayered cell membrane. The team consists of cell biologist Satyajit Mayor along with soft matter physicist Madan Rao and their teams at the National Centre for Biological Sciences, Bangalore, and synthetic chemists Ram Viswakarma (IIIM, Jammu) and Zhongwu Guo (Wayne State University, USA).

The team’s studies at the nanoscale have revealed that Phosphatidylserine (PS) is a key component that mediates the communication between the lipids on the inner leaflet, and actin and lipid-anchored proteins on the outer leaflet. PS gets the message across because of the presence of long chain-containing lipids such as those found in ‘solid fats’. That’s how the components on inner and outer leaflets communicate.  These studies show how integral PS is to signalling pathways of the cell, and therefore when absent results in irreparable damage.

“The uniqueness of the study lies in discovering a specific role for PS in nanocluster formation, a building block of ‘lipid rafts’ and how the chemistry of both the outer and inner leaflet facilitate this process. For this we have adopted an array of methods which combines biology, genetics, chemistry and physics to provide an explanation for the formation of nanoclusters” says Anupama Ambika Anilkumar, one of the first authors of the paper published online on 23 April, 2015, in the journal Cell.

Lipid rafts are microenvironments in the membrane made up of clusters of lipids and protein receptors, and are involved in molecule trafficking and assembly. Refuting early theories on the random combination of lipids to construct these lipid rafts, this study shows that the formation of these “nanoclusters” of lipids is an active process templated by the actin cytoskeleton on the inner leaflet. This understanding also points to further clues about the role of these clusters. They have been hypothesized to function as a ‘sorting station’ for components to be recruited for signalling events on the cell surface.

The discovery of PS as a vital component in the transmembrane communication would advance our understanding of the cell membrane’s microenvironment. It would also help scientists understand how these nanoclusters function and what proteins are involved in their assembly. Additional experiments in Mayor’s lab are underway to draw the complete picture of the cell’s communications and the anchors of the PS species. These entities also play an important role in various other cell functions and are hence important problems to pursue.

“There is no earlier evidence of how these clusters are formed by lipidic interactions. My colleague and co-first author, Riya Raghupathy established methods to assay the role of long-acyl chain lipid species, and along with Parvinder Pal Singh, developed the synthetic analogues used in this study. Anirban Polley, working with Madan, conducted molecular dynamic simulations; both of these are an integral part of this study and I am grateful for having such terrific collaborators,” said Anupama Anilkumar.

Decrypting this communication could help explain how signals are both read and interpreted by the cell, with implications for a number of diseases caused by alteration in lipid balance or composition. Understanding how these lipids, the “gatekeepers” of the cell, function might also help deter the progression of viral diseases, by potentially disrupting the interaction of membrane components with the viruses.

The paper can be accessed at:
http://dx.doi.org/10.1016/j.cell.2015.03.048

Replacement with a single atom alters thyroid biochemical cascade in the body

June 8, 2015

More than 200 million people worldwide suffer from thyroid related disorders like hyperthyroidism, hypothyroidism, goitre, Hashimoto’s thyroiditis, thyroid cancer etc. Hyperthyroidism is also associated with various diseases like Grave’s disease, thyroid storm and toxic thyroid nodule. Most of these are treated with synthetic form of T4 for hypothyrodism and thiouracil-based drugs for hyperthyroidism. However, small variations in the drug concentration can lead to adverse effects.

Thyroxine or T4, having four iodine atoms is the thyroid pro-hormone, while the biologically more active metabolite tri-iodothyronine (T3) regulates body temperature, growth and heart rate. Thyroxine is produced by the thyroid gland and its metabolism is tightly regulated in human body. The activation or inactivation of thyroid hormones are mediated by enzymes in various cells/tissues. The activation occurs when T4 is converted to T3, but an inactivation occurs when T4 is converted to reverse T3 (rT3).

Earlier studies showed that simple chemical compounds containing sulfur or selenium atoms can remove iodine atoms selectively from T4 to produce rT3, thereby, mimicking the enzymes that mediate the inactivation pathway. For the first time, K Raja and Prof. G Mugesh from the department of Inorganic and Physical Chemistry, IISc, Bangalore, show that the replacement of sulfur or selenium by tellurium atoms dramatically alters the rate of the reaction. The compounds that mediated the conversion of T4 to rT3 can also mediate the conversion of T4 to T3 upon introduction of a tellurium atom. This study shows how a single atom change in a chemical compound can alter a very important biochemical reaction.

The team of scientists have developed a novel set of compounds that can mimic the function of the enzymes to activate or inactivate thyroxine (i.e. remove iodine atoms from T4 under physiologically relevant conditions). Prof. Mugesh said, “While the primary aim of this study is to understand the various mechanisms proposed for the model reactions as well as those catalysed by the natural deiodinases, the compounds developed are considered as potential candidates for the development of drugs for thyroid related disorders such as hyperthyroidism.”

The team aims to develop compounds that can control the thyroxine metabolism in the body rather than inhibiting the thyroxine biosynthesis or supplementing with thyroxine. Depending upon the nature of disease, a suitable enzyme mimic can be administered. The advantage of the current set of compounds is that they are highly reactive and the deiodination reactions can be performed in water at physiological conditions. The previous studies used organic solvents for the chemical transformations, and such conditions are not suitable for drug development. Though the current studies indicate that the compounds have potential applications in the treatment of hyperthyroidism, they need to be tested in human cell lines and animal models to understand the efficacy and toxicity.

The article appeared in the “Early View” section of Angewandte Chemie on 12th May 2015. http://onlinelibrary.wiley.com/doi/10.1002/anie.201502762/abstract

– See more at: http://iisc.researchmedia.center/article/replacement-single-atom-alters-thyroid-biochemical-cascade-body#sthash.SOcHTTQI.dpuf

An “antioxidant-like” protein to fight free radical damage in the body

September 22, 2014

A protein found in high levels in some cancer cells can be used for treating diseases caused by oxygen free radicals in the body, a recent study has found.

Oxygen free radicals such as hydrogen peroxides and superoxides, called Reactive Oxygen Species (ROS), are found in the cells as byproducts of cellular metabolism. Uncontrolled levels of ROS in the cell can lead to oxidative stress. Diabetes, atherosclerosis and neurodegenerative diseases like Parkinson’s and Alzheimer’s disease find their roots at the damage caused by oxidative stress in the cells.

Patrick D’Silva’s group at the Indian Institute of Science have found that Magmas, a mitochondrial protein also regulates the level of ROS in cells, apart from its already known function.

Magmas is involved in protein transport in cells, and is found in elevated levels in certain cancer types. There is very little information already available about regulation of ROS in the body, and this paper brings forth a lot of missing links in this research area.

The team found that the levels of Magmas in the cell are dependent on the cellular ROS levels. Elevated levels of Magmas help in lowering the concentration of ROS and vice versa. It not only plays an important role in controlling the production of free radicals, but maintains the ROS homeostasis by efficient scavenging. This protects the cell viability and also increases cellular stress tolerance.

“By maintaining a free-radical balance in cell, this protein prevents stress mediated cellular damage to biomolecules such as DNA, proteins and lipids. Hence, overproduction of Magmas protein provides unique advantages to the cells against free radical stress”, said Prof D’Silva.

Higher levels of Magmas are typically found in metabolically active tissues, cancer cells and tissues at different developmental stages. In cancer cells, Magmas prevents cell death, and hence helps in the proliferation of cancer cells. Even in non-cancerous cells, Magmas shows controlled levels of ROS and much lesser oxidative stress.

Such molecules that regulate the number of free radicals can be used while designing possible therapies for oxidative stress related disorders. “The inhibitors or stimulators against Magmas can be used as a therapeutic intervention against cancer as well as multiple free-radical induced stress related diseases”, said Prof D’Silva.

Further research is required to elucidate the mechanism of ROS regulation by Magmas and to discover the other proteins involved in the regulatory circuit.

The paper appeared in the journal Cell Death and Disease on 28th August 2014.

Link: http://www.nature.com/cddis/journal/v5/n8/full/cddis2014355a.html

– See more at: http://iisc.researchmedia.center/article/%E2%80%9Cantioxidant-like%E2%80%9D-protein-fight-free-radical-damage-body#sthash.T0vXzIT9.dpuf

Conservation perceptions

July 2015

India, being rich in its biodiversity, needs to make space for both its ever growing human population as well as its wildlife to live in harmony within the limited supply of resources. Most of the laws and policies related to efficient utilisation of these resources for the sustenance of both population is decided primarily with the help of experts from the fields of ecology, conservation and environment. For the first time, a group of ecologists, environmental and conservation scientists, took a step in reaching out to the general public for their opinions and concerns. A nation-wide survey was conducted consisting of 572 respondents mostly from the educated, urban and sub-urban population who were asked to list up to 10 most important questions that need to be addressed for better management and conservation of biodiversity in the country. The final outcome of this large scale assessment has been summarised into a list of 152 questions spread across 17 broad themes. Within the high ranking topics of concerns were ‘Policy and Governance’, ‘Biodiversity and Endangered species’ and ‘Protection and Conservation’.

In previous surveys, mostly the experts or practitioners had taken part while this survey uniquely involves a whole wider population. The authors believed that a wider representation would help in highlighting the important issues as per the public and also help them avoid biases that experts tend to develop as a result of their knowledge in their respective fields of expertise. The involvement of people from various parts of the country also helped in identifying the emergent problems in the local contexts.

There is a pressing need to understand the changes in the environment and what drives the changes in it. The survey highlights the priority issues which can be used as a guiding framework for conservation practitioners, researchers, citizens, policy makers and funders to direct their effort’s in India’s conservation landscape. Many issues identified as a result of this survey are relevant at a global scale while there are many others that are of importance at smaller scales (country, region etc). Thus the region specific assessment helps in looking at customised solutions for the local conditions. Dr. Varun Varma, first author of the paper, said “our analysis reveals themes with lower than average emphasis compared to other studies, such as – marine ecosystems, ecosystem function and services. The lack of emphasis is suggestive of lower awareness and/or press coverage of issues within these themes.”

Most of the respondents of the survey was limited to the literate section of the urban areas. Subsequent surveys could use more resources like the print media, and manpower in order to be more inclusive of the participants. Usage of vernacular languages could help reaching out to the rural population also. Nevertheless the present study was a huge leap in widening the representative class of citizens in the environmental and ecological issues in the Indian context. People are an integral part of the conservation of biodiversity and ecosystems. Their active participation helps policy makers and scientists make better decisions.