Navigation Links
Chemical liberated by leaky gut may allow HIV to infect the brain, Einstein scientists find

In up to 20 percent of people infected with HIV, the virus manages to escape from the bloodstream and cross into the brain, resulting in HIV-associated dementia and other cognitive disorders. Now, scientists at the Albert Einstein College of Medicine of Yeshiva University have found strong evidence that a component of the cell walls of intestinal bacteriaa chemical present in high levels in the blood of HIV-infected peoplehelps HIV to penetrate the usually-impregnable blood brain barrier (BBB). The findings, published in the August issue of the Journal of Virology, could lead to strategies for preventing HIV from entering the brain and causing serious complications.

"Previous research has suggested that it's not individual HIV viruses that get into the brain but rather HIV-infected immune cells known as monocytes," says Dr. Harris Goldstein, director of the Einstein-Montefiore Medical Center for AIDS Research and senior author of the study. "Using an animal model, we wanted to find out first of all whether being infected with HIV enables monocytes to do what they don't usually doescape from blood vessels and enter brain tissue."

Overcoming HIV's inability to infect mice, Dr. Goldstein and his colleagues had previously created a transgenic mouse line, HIV-TG mice, equipped with all the genes needed to make HIVand that produces HIV in those cells, including monocytes and T cells, in which the virus multiplies in people. The HIV-TG mice were then bred with another transgenic mouse line, GFP-TG mice, containing the gene that codes for green fluorescent protein (GFP). The result: a double transgenic mouse line, HIV/GFP-TG mice, whose HIV-infected monocytes carried the GFP gene. This meant that the monocytes could be detectedeither by looking for glowing green cells under the microscope or by using polymerase chain reaction, a sensitive genetic assay capable of detecting the DNA of the GFP gene.

Next, the researchers isolated millions of monocytesHIV/GFP-producing monocytes from the HIV/GFP-TG mice, and monocytes from the GFP-TG mice producing GFP aloneand injected each type of monocyte into control mice.

Four days later, the researchers examined the brains of the injected mice to see whether monocytes from the bloodstream had crossed their BBB's. While there was no sign of monocytes in the brains of any of the mice injected with uninfected GFP monocytes, ultrasensitive DNA analysis showed that HIV/GFP monocytes were present at very low levels in the brains of nearly one third of the mice injected with the HIV-producing monocytes. "These results demonstrated very clearly that being infected with HIV somehow gives monocytes the capacity to cross an intact BBB," says Dr. Goldstein. "But we also suspected that something else was making it easier for HIV-infected monocytes to breach the defenses protecting the brain from infection."

In 2006, scientists at the National Institutes of Health had reported that HIV infection breaks down barriers in the intestine that normally prevent intestinal bacteria from entering the bloodstream. The blood of HIV-infected people was found to contain markedly elevated levels of lipopolysaccharide (LPS), a component of certain bacteria that are normally confined to the intestine but leak out due to HIV infection. In addition, previous animal studies had shown that exposure to elevated LPS levels compromised the integrity of the BBB. "So we hypothesized that the combination of HIV-infected monocytes and elevated LPS levels would amplify the ability of HIV to cross the BBB and get into the brain," says Dr. Goldstein.

To test this hypothesis, his team injected control mice with very low doses of LPS that were comparable to the levels in the bloodstream of HIV-infected individuals and would only minimally weaken their BBB's. Three hours later, half the mice were intravenously injected with HIV-and-GFP-producing monocytes, while the remaining mice were intravenously injected with GFP-producing monocytes that were otherwise normal.

Four days later, monocytes could not be detected in the brains of any of the 15 mice that were pre-treated with LPS and then injected with normal monocytes producing GFP alone. By contrast, monocytes were readily detected in the brains of about 25% of mice pre-treated with LPS and then injected with HIV-and-GFP-producing monocytes.

"Clearly, HIV-infected monocytes uniquely benefit from the LPS that is present in high amounts in the blood of HIV-infected people," says Dr. Goldstein. "So when HIV-infected monocytes are 'knocking on the door' of the BBB and starting to crack it open, the LPS facilitates their entry by making the BBB more permeable, apparently by weakening blood vessel structure."

If HIV-infected monocytes and LPS in the bloodstream can be considered a one-two punch for entry into the brain, a third punchsimply having a systemic HIV infectionalso seems to help soften up the BBB. In making this discovery, Dr. Goldstein used his HIV-TG mouse strain, in which HIV is known to replicate inside brain cells associated with the BBB. These HIV-TG mice, along with control mice, were injected with LPS and, three hours later, intravenously injected with HIV-and-GFP-producing monocytes from the HIV/GFP-TG mouse strain.

Four days later, HIV-producing monocytes could be detected in the brains of about 25 percent of the control mice, as in the preceding experiment. By contrast, more than twice as many (70 percent) of the brains of HIV-TG mice that support systemic HIV infection contained HIV-producing monocytes. Even more impressive: When present, HIV-producing monocytes were three times more numerous in the brains of HIV-TG mice than in the brains of control mice.

"These results demonstrate very dramatically that HIV infection of cells associated with the BBB, in conjunction with LPS exposure, contributes to BBB breakdown," says Dr. Goldstein. (See slides below). "So when HIV infection occurs, we seem to have a 1-2-3 combination of punches working in concert to facilitate entry of HIV-infected monocytes into the BBB-protected brain: HIV infection of monocytes increases their capacity to cross even an intact BBB; HIV infection in the gut releases LPS into the bloodstream allowing it to erode the BBB; and HIV infection of the cells of the BBB makes them more sensitive to the deleterious effects of LPS."

These findings could lead to preventive or therapeutic strategies. To help maintain the integrity of the BBB in HIV-infected people, says Dr. Goldstein, one approach might be to monitor the LPS level in their bloodstream and then reduce elevated levels. "We may be able to use antibiotics that kill intestinal bacteria that make LPS, and drugs are already available that can bind to LPS and clear it from the bloodstream," says Dr. Goldstein. "Ideally, we would promptly start newly diagnosed HIV-infected patients on a treatment to reinforce their BBB's so that HIV can't penetrate itand perhaps we could even strengthen the BBB's of people who've been infected for quite a while. But before we can prevent the tragedy of HIV-associated dementia, we need to better understand the mechanism by which these molecular and cellular 'punches' interact to undermine the BBB."


Contact: Michael Heller
Albert Einstein College of Medicine

Related medicine news :

1. Black Henna Tattoo Chemical Can Cause Skin Reaction
2. Lawmakers Agree to Ban Dangerous Chemicals in Toys
3. Most Influential Events for Koreas Fine and Specialty Chemical and Pharmaceutical Industries to be Held in November
4. Stay Safe This Summer With Chemical-Free Sunscreen and DEET-Free Bug Repellent, Says Natural Solutions Magazine
5. Clean, Chemical-Free Eye Cream Evening Primrose Oil: The Puffy-Eye Cure
6. SIDS Linked to Brain Chemical Dysfunction
7. CEVA Logistics Awarded Best 3PL Provider for Pharmaceutical, Chemical, HazMat and Fresh Food Supply Chains
8. American Chemical Societys Weekly PressPac -- June 18, 2008
9. American Chemical Societys Weekly PressPac: June 11, 2008
10. UCR chemists use green chemistry to produce amines, chemical compounds used widely in industry
11. Pfizers work on penicillin for World War II becomes a National Historic Chemical Landmark
Post Your Comments:
Related Image:
Chemical liberated by leaky gut may allow HIV to infect the brain, Einstein scientists find
(Date:11/25/2015)... ... November 25, 2015 , ... “While riding the bus, I ... Bronx, N.Y. “I thought there had to be a convenient and comfortable way to ... The PROTECTOR enables disabled individuals to safely travel during cold or inclement weather. In ...
(Date:11/25/2015)... , ... November 25, 2015 , ... ... (PHA) announces the nation’s Periwinkle Pioneers, individuals and groups responsible for advancing care ... disease. The Periwinkle Pioneers, nominated by the public, will receive special recognition throughout ...
(Date:11/25/2015)... ... November 25, 2015 , ... ... philanthropic seniors, is resulting in a way for homeless people to have a ... have launched a new initiative whereby they are repurposing plastic bags into sleeping ...
(Date:11/25/2015)... ... November 25, 2015 , ... Since its launch in 2012, ... adult stem cell therapies to patients with chronic degenerative medical conditions. Now, the ... Registered Trademark (RTM). , Organizations are required to hold a registered trademark in ...
(Date:11/24/2015)... ... November 25, 2015 , ... Genesis Chiropractic Software ... software creates an agreement between the practice owner and the patient that automatically ... notification, and projections. Click here to learn more. , ...
Breaking Medicine News(10 mins):
(Date:11/24/2015)... FRANCISCO , Nov. 24, 2015  Thanks to ... Dignity Health St. Mary,s Medical Center,s Sister Diane Grassilli ... breast imaging capabilities in San Francisco ... an anonymous friend, stepped forward with a gift of ... for Breast Digital Mammography with Tomosynthesis and Whole Breast ...
(Date:11/24/2015)... Colo. , Nov. 24, 2015  Array ... that its Chief Executive Officer, Ron Squarer ... Healthcare Conference in New York.  The public is ... webcast on the Array BioPharma website.Event:Piper Jaffray Annual ... , Wednesday, December 2, 2015Time:1:30 p.m. Eastern Time ...
(Date:11/24/2015)... HOUSTON, TX and VANCOUVER, Nov. 24, 2015 /PRNewswire/ ... EPI; NASDAQ: EPIX ) announced today that the ... clinical study of EPI-506 as a treatment for metastatic ... States and Canada.  --> ... --> In the Phase 1/2 clinical trial, ...
Breaking Medicine Technology: