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SAN FRANCISCO – A novel therapeutic strategy shows initial promise in dampening hepatic cell injury in mice caused by overexposure to acetaminophen. The approach relies on a synthetic version of heparan sulfate, which is believed to interfere with recruitment of neutrophils to the site of hepatic injury. That reduces harm caused by inflammation and may offer a longer therapeutic window than N-acetyl cysteine, which is the current standard therapy but is only effective if given within 8 hours of the injury.
The endogenous syndecan-1, which is a heparan sulfate, is also known to act as a native defense mechanism against inflammatory injury to hepatocytes. “It looks like heparan sulfate attenuates inflammatory responses,” said Jian Liu, PhD, during a presentation of his research at the annual meeting of the American Association for the Study of Liver Diseases. Dr. Liu is a professor of chemical biology and medicinal chemistry at the University of North Carolina at Chapel Hill.
The heparan sulfate analogue heparin has long been used as an anticoagulant, of course, which suggests that a novel heparan sulfate has a good chance of also being safe.
Dr. Liu’s team had to identify a heparan sulfate that had a hepatoprotective effect, but a heparan sulfate’s unique biological activity depends on the specific pattern of sulfation on the heparan molecule. Heparans isolated from natural sources are generally a complex mixture, which makes them difficult to study and produce in large enough quantities to be therapeutically useful.
Dr. Liu’s team used a combinatory approach, harnessing various enzymes to produce hundreds of different heparan sulfate variants, and then screened them for hepatoprotective activity. That process identified an 18-chain heparan sulfate with hepatoprotective activity. With an active formula in hand, they could employ the enzymes to create enough of the pure compound to further the research. “It’s probably two to three hundred times more efficient than the traditional chemical synthesis,” said Dr. Liu.
In mice, researchers injected the 18-mer 30 minutes after a hepatotoxic dose of acetaminophen and again after 12 hours. Tissue staining showed less migration of neutrophils, as well as lower concentrations of tumor necrosis factor–alpha. The animals also had lower alanine transferase levels than did the untreated animals, as well as greater survival after 4 days.
The pathological process surrounding acetaminophen overdose involves release of the high mobility group box 1 (HMGB1) protein from necrotic hepatocytes, which in turn binds to the receptor for advanced glycation end-products (RAGE). The HMGB1/RAGE complex then binds to neutrophils, recruiting them to the site of the injury and initiating inflammation.
To better understand the molecule’s role in the pathological process, the researchers studied RAGE knockout mice, and found that the 18-mer had no protective effect in these animals, suggesting that it relies on RAGE for its biological activity.
Heparan sulfates are widely present in the body, which prompted the researchers to investigate their endogenous effect. In the liver, the primary heparan sulfate is syndecan-1. The researchers demonstrated that the molecule is shed from cell surfaces in response to acetaminophen toxicity and that the levels correlate with HMGB1 release.
Dr. Liu believes that syndecan-1 acts as a natural buffer to inflammation, helping to neutralize HMGB1 and limit damage. “The problem is that when the damage is massive, the shed of syndecan-1 is not enough,” said Dr. Liu. He hopes that something like his team’s heparan sulfate 18-mer can be used therapeutically to bolster these endogenous controls and prevent further damage.
The research was funded by Glycan Therapeutics. Dr. Liu founded Glycan, which offers custom-synthesized heparan sulfates and chondroitin sulfates for research purposes.
SOURCE: Liu J. AASLD 2018, Abstract 0040.
SAN FRANCISCO – A novel therapeutic strategy shows initial promise in dampening hepatic cell injury in mice caused by overexposure to acetaminophen. The approach relies on a synthetic version of heparan sulfate, which is believed to interfere with recruitment of neutrophils to the site of hepatic injury. That reduces harm caused by inflammation and may offer a longer therapeutic window than N-acetyl cysteine, which is the current standard therapy but is only effective if given within 8 hours of the injury.
The endogenous syndecan-1, which is a heparan sulfate, is also known to act as a native defense mechanism against inflammatory injury to hepatocytes. “It looks like heparan sulfate attenuates inflammatory responses,” said Jian Liu, PhD, during a presentation of his research at the annual meeting of the American Association for the Study of Liver Diseases. Dr. Liu is a professor of chemical biology and medicinal chemistry at the University of North Carolina at Chapel Hill.
The heparan sulfate analogue heparin has long been used as an anticoagulant, of course, which suggests that a novel heparan sulfate has a good chance of also being safe.
Dr. Liu’s team had to identify a heparan sulfate that had a hepatoprotective effect, but a heparan sulfate’s unique biological activity depends on the specific pattern of sulfation on the heparan molecule. Heparans isolated from natural sources are generally a complex mixture, which makes them difficult to study and produce in large enough quantities to be therapeutically useful.
Dr. Liu’s team used a combinatory approach, harnessing various enzymes to produce hundreds of different heparan sulfate variants, and then screened them for hepatoprotective activity. That process identified an 18-chain heparan sulfate with hepatoprotective activity. With an active formula in hand, they could employ the enzymes to create enough of the pure compound to further the research. “It’s probably two to three hundred times more efficient than the traditional chemical synthesis,” said Dr. Liu.
In mice, researchers injected the 18-mer 30 minutes after a hepatotoxic dose of acetaminophen and again after 12 hours. Tissue staining showed less migration of neutrophils, as well as lower concentrations of tumor necrosis factor–alpha. The animals also had lower alanine transferase levels than did the untreated animals, as well as greater survival after 4 days.
The pathological process surrounding acetaminophen overdose involves release of the high mobility group box 1 (HMGB1) protein from necrotic hepatocytes, which in turn binds to the receptor for advanced glycation end-products (RAGE). The HMGB1/RAGE complex then binds to neutrophils, recruiting them to the site of the injury and initiating inflammation.
To better understand the molecule’s role in the pathological process, the researchers studied RAGE knockout mice, and found that the 18-mer had no protective effect in these animals, suggesting that it relies on RAGE for its biological activity.
Heparan sulfates are widely present in the body, which prompted the researchers to investigate their endogenous effect. In the liver, the primary heparan sulfate is syndecan-1. The researchers demonstrated that the molecule is shed from cell surfaces in response to acetaminophen toxicity and that the levels correlate with HMGB1 release.
Dr. Liu believes that syndecan-1 acts as a natural buffer to inflammation, helping to neutralize HMGB1 and limit damage. “The problem is that when the damage is massive, the shed of syndecan-1 is not enough,” said Dr. Liu. He hopes that something like his team’s heparan sulfate 18-mer can be used therapeutically to bolster these endogenous controls and prevent further damage.
The research was funded by Glycan Therapeutics. Dr. Liu founded Glycan, which offers custom-synthesized heparan sulfates and chondroitin sulfates for research purposes.
SOURCE: Liu J. AASLD 2018, Abstract 0040.
SAN FRANCISCO – A novel therapeutic strategy shows initial promise in dampening hepatic cell injury in mice caused by overexposure to acetaminophen. The approach relies on a synthetic version of heparan sulfate, which is believed to interfere with recruitment of neutrophils to the site of hepatic injury. That reduces harm caused by inflammation and may offer a longer therapeutic window than N-acetyl cysteine, which is the current standard therapy but is only effective if given within 8 hours of the injury.
The endogenous syndecan-1, which is a heparan sulfate, is also known to act as a native defense mechanism against inflammatory injury to hepatocytes. “It looks like heparan sulfate attenuates inflammatory responses,” said Jian Liu, PhD, during a presentation of his research at the annual meeting of the American Association for the Study of Liver Diseases. Dr. Liu is a professor of chemical biology and medicinal chemistry at the University of North Carolina at Chapel Hill.
The heparan sulfate analogue heparin has long been used as an anticoagulant, of course, which suggests that a novel heparan sulfate has a good chance of also being safe.
Dr. Liu’s team had to identify a heparan sulfate that had a hepatoprotective effect, but a heparan sulfate’s unique biological activity depends on the specific pattern of sulfation on the heparan molecule. Heparans isolated from natural sources are generally a complex mixture, which makes them difficult to study and produce in large enough quantities to be therapeutically useful.
Dr. Liu’s team used a combinatory approach, harnessing various enzymes to produce hundreds of different heparan sulfate variants, and then screened them for hepatoprotective activity. That process identified an 18-chain heparan sulfate with hepatoprotective activity. With an active formula in hand, they could employ the enzymes to create enough of the pure compound to further the research. “It’s probably two to three hundred times more efficient than the traditional chemical synthesis,” said Dr. Liu.
In mice, researchers injected the 18-mer 30 minutes after a hepatotoxic dose of acetaminophen and again after 12 hours. Tissue staining showed less migration of neutrophils, as well as lower concentrations of tumor necrosis factor–alpha. The animals also had lower alanine transferase levels than did the untreated animals, as well as greater survival after 4 days.
The pathological process surrounding acetaminophen overdose involves release of the high mobility group box 1 (HMGB1) protein from necrotic hepatocytes, which in turn binds to the receptor for advanced glycation end-products (RAGE). The HMGB1/RAGE complex then binds to neutrophils, recruiting them to the site of the injury and initiating inflammation.
To better understand the molecule’s role in the pathological process, the researchers studied RAGE knockout mice, and found that the 18-mer had no protective effect in these animals, suggesting that it relies on RAGE for its biological activity.
Heparan sulfates are widely present in the body, which prompted the researchers to investigate their endogenous effect. In the liver, the primary heparan sulfate is syndecan-1. The researchers demonstrated that the molecule is shed from cell surfaces in response to acetaminophen toxicity and that the levels correlate with HMGB1 release.
Dr. Liu believes that syndecan-1 acts as a natural buffer to inflammation, helping to neutralize HMGB1 and limit damage. “The problem is that when the damage is massive, the shed of syndecan-1 is not enough,” said Dr. Liu. He hopes that something like his team’s heparan sulfate 18-mer can be used therapeutically to bolster these endogenous controls and prevent further damage.
The research was funded by Glycan Therapeutics. Dr. Liu founded Glycan, which offers custom-synthesized heparan sulfates and chondroitin sulfates for research purposes.
SOURCE: Liu J. AASLD 2018, Abstract 0040.
REPORTING FROM AASLD 2018