Tumors Feel The Deadly Sting Of Nanobees

Tumors Feel The Deadly Sting Of Nanobees

  1:59:00 AM    Science Lover

---

When bees sting, they pump poison into their victims. Now the toxin in bee venom has been harnessed to kill tumor cells by researchers at Washington University School of Medicine in St. Louis. The researchers attached the major component of bee venom to nano-sized spheres that they call nanobees.

Bee on a finger. Researchers have recently harnessed the toxin in bee venom
to kill tumor cells. (Credit: iStockphoto/Tatiana Buzuleac)

In mice, nanobees delivered the bee toxin melittin to tumors while protecting other tissues from the toxin's destructive power. The mice's tumors stopped growing or shrank. The nanobees' effectiveness against cancer in the mice is reported in advance online publication Aug. 10 in the Journal of Clinical Investigation.

"The nanobees fly in, land on the surface of cells and deposit their cargo of melittin which rapidly merges with the target cells," says co-author Samuel Wickline, M.D., who heads the Siteman Center of Cancer Nanotechnology Excellence at Washington University. "We've shown that the bee toxin gets taken into the cells where it pokes holes in their internal structures."

Melittin is a small protein, or peptide, that is strongly attracted to cell membranes, where it can form pores that break up cells and kill them.

"Melittin has been of interest to researchers because in high enough concentration it can destroy any cell it comes into contact with, making it an effective antibacterial and antifungal agent and potentially an anticancer agent," says co-author Paul Schlesinger, M.D., Ph.D., associate professor of cell biology and physiology. "Cancer cells can adapt and develop resistance to many anticancer agents that alter gene function or target a cell's DNA, but it's hard for cells to find a way around the mechanism that melittin uses to kill."

The scientists tested nanobees in two kinds of mice with cancerous tumors. One mouse breed was implanted with human breast cancer cells and the other with melanoma tumors. After four to five injections of the melittin-carrying nanoparticles over several days, growth of the mice's breast cancer tumors slowed by nearly 25 percent, and the size of the mice's melanoma tumors decreased by 88 percent compared to untreated tumors.

The researchers indicate that the nanobees gathered in these solid tumors because tumors often have leaky blood vessels and tend to retain material. Scientists call this the enhanced permeability and retention effect of tumors, and it explains how certain drugs concentrate in tumor tissue much more than they do in normal tissues.

But the researchers also developed a more specific method for making sure nanobees go to tumors and not healthy tissue by loading the nanobees with additional components. When they added a targeting agent that was attracted to growing blood vessels around tumors, the nanobees were guided to precancerous skin lesions that were rapidly increasing their blood supply. Injections of targeted nanobees reduced the extent of proliferation of precancerous skin cells in the mice by 80 percent.

Overall, the results suggest that nanobees could not only lessen the growth and size of established cancerous tumors but also act at early stages to prevent cancer from developing.

"Nanobees are an effective way to package the useful, but potentially deadly, melittin, sequestering it so that it neither harms normal cells nor gets degraded before it reaches its target," Schlesinger says.

If a significant amount of melittin were injected directly into the bloodstream, widespread destruction of red blood cells would result. The researchers showed that nanoparticles protected the mice's red cells and other tissues from the toxic effects of melittin. Nanobees injected into the bloodstream did not harm the mice. They had normal blood counts, and tests for the presence of blood-borne enzymes indicative of organ damage were negative.

When secured to the nanobees, melittin is safe from protein-destroying enzymes that the body produces. Although unattached melittin was cleared from the mice's circulation within minutes, half of the melittin on nanobees was still circulating 200 minutes later. Schlesinger indicates that is long enough for the nanobees to circulate through the mice's bloodstream 200 times, giving them ample time to locate tumors.

"Melittin is a workhorse," says Wickline, also professor of medicine in the Cardiovascular Division and professor of physics, of biomedical engineering and of cell biology and physiology. "It's very stable on the nanoparticles, and it's easily and cheaply produced. We are now using a nontoxic part of the melittin molecule to hook other drugs, targeting agents or imaging compounds onto nanoparticles."

The core of the nanobees is composed of perfluorocarbon, an inert compound used in artificial blood. The research group developed perfluorocarbon nanoparticles several years ago and have been studying their use in various medical applications, including diagnosis and treatment of atherosclerosis and cancer. About six millionths of an inch in diameter, the nanoparticles are large enough to carry thousands of active compounds, yet small enough to pass readily through the bloodstream and to attach to cell membranes.

"We can add melittin to our nanoparticles after they are built," Wickline says. "If we've already developed nanoparticles as carriers and given them a targeting agent, we can then add a variety of components using native melittin or melittin-like proteins without needing to rebuild the carrier. Melittin fortunately goes onto the nanoparticles very quickly and completely and remains on the nanobee until cell contact is made."

The flexibility of nanobees and other nanoparticles made by the group suggests they could be readily adapted to fit medical situations as needed. The ability to attach imaging agents to nanoparticles means that the nanoparticles can give a visible indication of how much medication gets to tumors and how tumors respond.

"Potentially, these could be formulated for a particular patient," Schlesinger says. "We are learning more and more about tumor biology, and that knowledge could soon allow us to create nanoparticles targeted for specific tumors using the nanobee approach."

Funding from the National Institutes of Health and the American Heart Association supported this research.

If you like this post, buy me a Pittza at $1!

Read More

New Nanoparticles Could Lead To End Of Chemotherapy

New Nanoparticles Could Lead To End Of Chemotherapy

  9:56:00 PM    Science Lover

---

Nanoparticles specially engineered by University of Central Florida Assistant Professor J. Manuel Perez and his colleagues could someday target and destroy tumors, sparing patients from toxic, whole-body chemotherapies.

Dr. Manuel Perez and his team have been investigating
the use of nanoparticles for medicine for years.
(Credit: Jacque Brund)

Perez and his team used a drug called Taxol for their cell culture studies, recently published in the journal Small, because it is one of the most widely used chemotherapeutic drugs. Taxol normally causes many negative side effects because it travels throughout the body and damages healthy tissue as well as cancer cells.

The Taxol-carrying nanoparticles engineered in Perez's laboratory are modified so they carry the drug only to the cancer cells, allowing targeted cancer treatment without harming healthy cells. This is achieved by attaching a vitamin (folic acid) derivative that cancer cells like to consume in high amounts.

Because the nanoparticles also carry a fluorescent dye and an iron oxide magnetic core, their locations within the cells and the body can be seen by optical imaging and magnetic resonance imaging (MRI). That allows a physician to see how the tumor is responding to the treatment.

The nanoparticles also can be engineered without the drug and used as imaging (contrast) agents for cancer. If there is no cancer, the biodegradable nanoparticles will not bind to the tissue and will be eliminated by the liver. The iron oxide core will be utilized as regular iron in the body.

"What's unique about our work is that the nanoparticle has a dual role, as a diagnostic and therapeutic agent in a biodegradable and biocompatible vehicle," Perez said.

Perez has spent the past five years looking at ways nanotechnology can be used to help diagnose, image and treat cancer and infectious diseases. It's part of the quickly evolving world of nanomedicine.

The process works like this. Cancer cells in the tumor connect with the engineered nanoparticles via cell receptors that can be regarded as "doors" or "docking stations." The nanoparticles enter the cell and release their cargo of iron oxide, fluorescent dye and drugs, allowing dual imaging and treatment.

"Although the results from the cell cultures are preliminary, they are very encouraging," Perez said.

A new chemistry called "click chemistry" was utilized to attach the targeting molecule (folic acid) to the nanoparticles. This chemistry allows for the easy and specific attachment of molecules to nanoparticles without unwanted side products. It also allows for the easy attachment of other molecules to nanoparticles to specifically seek out particular tumors and other malignancies.

Perez's study builds on his prior research published in the prestigious journal Angewandte Chemie Int. Ed. His work has been partially funded by a National Institutes of Health grant and a Nanoscience Technology Center start-up fund.

"Our work is an important beginning, because it demonstrates an avenue for using nanotechnology not only to diagnose but also to treat cancer, potentially at an early stage," Perez said.

Perez, a Puerto Rico native, joined UCF in 2005. He works at UCF's NanoScience Technology Center and Chemistry Department and in the Burnett School of Biomedical Sciences in the College of Medicine. He has a Ph.D. from Boston University in Biochemistry and completed postdoctoral training at Massachusetts General Hospital, Harvard Medical School's teaching and research hospital.

If you like this post, buy me a beer at $3!

Read More

Sleep: Spring Cleaning For The Brain?

Sleep: Spring Cleaning For The Brain?

  11:06:00 AM    Science Lover

---

On the left, the brain of the well-rested blue fly has low levels of a synaptic protein called BRP in this 3D view from a confocal mircoscope. On the right, the brain of the sleep-deprived fly glows orange in areas of BRP concentration. (Bruchpilot or BRP is a protein involved in communication between neurons.)In the tired fly, the protein is present at high concentartions in three major areas of the fly's brain that are associated with learning. Sleep reduces the levels of this protein, an indication that synapses get smaller and/or weaker. This process of "downscaling" may be important so the brain is reset to normal levels of synaptic activity and can begin learning again the next day. (Credit: Courtesy of UW Health Public Affairs)

If you've ever been sleep-deprived, you know the feeling that your brain is full of wool.

Now, a study published in the April 3 edition of the journal Science has molecular and structural evidence of that woolly feeling — proteins that build up in the brains of sleep-deprived fruit flies and drop to lower levels in the brains of the well-rested. The proteins are located in the synapses, those specialized parts of neurons that allow brain cells to communicate with other neurons.

Sleep researchers at the University of Wisconsin-Madison School of Medicine and Public Health believe it is more evidence for their theory of "synaptic homeostasis." This is the idea that synapses grow stronger when we're awake as we learn and adapt to an ever-changing the environment, that sleep refreshes the brain by bringing synapses back to a lower level of strength. This is important because larger synapses consume a lot of energy, occupy more space and require more supplies, including the proteins examined in this study.

Sleep — by allowing synaptic downscaling — saves energy, space and material, and clears away unnecessary "noise" from the previous day, the researchers believe. The fresh brain is then ready to learn again in the morning.

The researchers — Giorgio Gilestro, Giulio Tononi and Chiara Cirelli, of the Center for Sleep and Consciousness — found that levels of proteins that carry messages in the synapses (or junctions) between neurons drop by 30 to 40 percent during sleep.

In the Science paper, three-dimensional photos using confocal microscopy show the brains of sleep-deprived flies filled with a synaptic protein called Bruchpilot (BRP), a component of the machinery that allows communication among neurons. In well-rested flies, levels of BRP and four other synaptic proteins drop back to low levels, providing evidence that sleep resets the brain to allow more growth and learning the next day.

"We know that sleep is necessary for our brain to function properly, to learn new things every day, and also, in some cases, to consolidate the memory of what we learned during the day," says Cirelli, associate professor of psychiatry. "During sleep, we think that most, if not all, synapses are downscaled: at the end of sleep, the strongest synapses shrink, while the weakest synapses may even disappear."

The confocal microscope views show this happening in all three major areas of the fruit-fly brain, which are known to be very plastic (involved in learning).

In a paper published last year, Tononi, Cirelli and their co-investigators found similar chemical changes in the synapses of rats' brains. They also showed that rats' brains have a stronger "evoked response" to electrical stimulation after being awake, and a weaker one after sleep. That finding provided more evidence, using electrophysiological rather than molecular techniques, consistent with the idea that synapses grow stronger during the day, then weaker during sleep.

Because sleep performs the same function in the brains of species as diverse as fruit flies and rats, Cirelli says it was likely conserved by evolution because it is so important to an animal's health and survival.

The Wisconsin laboratory has pioneered ways of studying sleep in different species, including fruit flies.

To keep the flies awake, they're put into a "fly agitator" that holds 10 plates, each containing 32 drowsy flies. A robot arm shakes the plates occasionally to keep the flies from dozing.

Flies were deprived of sleep for as long as 24 hours. Researchers then dissected their brains and measured the levels of four pre-synaptic proteins and one post-synaptic protein. All levels rose progressively during periods of wakefulness and fell after sleep. Other experiments confirmed that the changes in protein levels were not caused by exposure to light and darkness or by the stimulation itself, but by sleep and waking. They also used confocal microscopy and an antibody that specifically recognizes BRP to measure the expression of this protein in many fly-brain areas.

Higher levels of these synaptic proteins during waking may be evidence of random experiences that fill the brain every day and need to be dissipated to make room for the learning and memories that are truly significant.

"Much of what we learn in a day, we don't really need to remember," Cirelli says. "If you've used up all the space, you can't learn more before you clean out the junk that is filling up your brain."

==================================================================

Journal reference:

1. Giorgio F. Gilestro, Giulio Tononi, and Chiara Cirelli. Widespread Changes in Synaptic Markers as a Function of Sleep and Wakefulness in Drosophila. Science, 2009; 324 (5923): 109 DOI: 10.1126/science.1166673

Adapted from materials provided by University of Wisconsin-Madison.

If you like this post, buy me a beer at $3!

Read More