Every year some 10,000 burn victims in the United States undergo an acute inflammatory reaction and die of burn-related infections, according to the Centers for Disease Control and Prevention.
Now a newly published study by a research team from the laboratory of distinguished professor Bruce Hammock, University of California, Davis, and the Department of Surgery, University of Cincinnati College of Medicine (UC CoM), has identified a key regulatory mechanism in inflammation that may lead to new targets for resolving that inflammation—and the inflammation of patients with sepsis, cancer and COVID.
In research published in the current edition of Proceedings of the Natural Academy of Sciences, the scientists announced that they have discovered a pathway that regulates the immune response after infection or injury, such as burns. Dysregulation of this pathway could differentiate those who are at risk of fatal sepsis or help identify targets to resolve this unregulated inflammation.
“We are very excited about the findings in this paper and the far-reaching impacts it could have on understanding a key regulatory step in the immune response,” said co-lead author and researcher Cindy McReynolds of the Hammock lab and director of research at EicOsis, a Davis-based company founded by Hammock. Hammock, the corresponding author of the publication, has been involved in enzyme research for more than 50 years.
“Our previous work identified that these same lipid mediators were up-regulated in severe COVID infections, and we are now finding that these compounds play a role in modulating the immune response so that the body is unable to fight infection or respond properly to trauma without leading to a potentially fatal overreaction,” said McReynolds, who holds a doctorate in pharmacology and toxicology from UC Davis.
“The immunological disbalance we see in many cases of severe burn injury, trauma and sepsis pose a huge clinical challenge as we lack the understanding of how to diagnose and treat it,” said co-lead author Dr. Christian Bergmann, formerly with UC CoM's Department of Surgery and now headquartered in Germany with the University of Ulm's Department of Trauma Surgery, Hand, Plastic and Reconstructive Surgery. “With this work, we reveal an important mechanism how immune cells are functionally disabled by sEH-derived metabolites of linoleic acid.”
“The natural compounds we are studying in this paper are metabolites of linoleic acid (LA), an essential fatty acid the body needs in very small amounts to survive and is only available through the diet,” McReynolds explained. “At lower concentrations, these metabolites are necessary for regulating thermogenesis and heart health but promote inflammation at higher concentrations. LA is more stable and much cheaper than longer chain polyunsaturated fatty acids, so heavily processed foods have higher LA content to increase shelf-life. Additionally, agricultural practices, such as feeding animals corn-based diets, have increased LA in meats and dairy products.”
The research, titled "sEH-Derived Metabolites of Linoleic Acid Drive Pathologic Inflammation while Impairing Key Innate Immune Cell Function in Burn Injury,” is co-authored by Debin Wan, formerly of the Hammock lab and now a scientist at Escape Bio, San Francisco; Nalin Singh of the Hammock lab; and three UC CoM researchers: Charles Caldwell, professor and director, Division of Research, Department of Surgery; Dorothy Supp, adjunct professor in the Department of Surgery and a scientific staff member at Shriners Children's Ohio; and Holly Goetzman, principal research assistant in the Caldwell lab.
“Chronic pain is an enormous emotional and economic burden for more than 100 million people in the United States alone,” said co-author Hammock, who holds a joint appointment with the Department of Entomology and Nematology and the UC Davis Comprehensive Cancer Center. "The extreme and poorly treated pain that I observed as a medical officer working in a burn clinic in the Army, is a major driver for me to translate laboratory research to help patients with severe pain and at risk from sepsis." Another major influence: his mother served 15 years as a nurse in a children's hospital burn center, caring for hundreds of patients.
Hammock founded EicOsis in December 2011 to advance novel, safe and effective oral treatments for patients suffering from pain and inflammation. The LLC is developing a new class of oral non-narcotic analgesics based on inhibition of the soluble epoxide hydrolase enzyme. Human clinical trials are underway to test the drug candidate, EC5026, a first-in-class, small molecule that potently inhibits sEH. The sEH inhibitors have already shown to be effective for inflammatory and neuropathic pain in animals, with no apparent adverse or addictive reactions.
Several grants supported the research: Dr. Bergmann received a grant from Deutsche Forschungsgemeinschaft (German Research Foundation) and a National Institutes of Health (NIH) grant from the National Institute of General Medical Sciences (NIGMS); Supp, a grant from the Shriners Hospitals for Children; and Hammock, a RIVER (Revolutionizing Innovative Visionary, Environmental Health) grant from the NIH's National Institute of Environmental Health (NIEHS), and an NIH/NIEHS Superfund Program grant. Hammock has directed the UC Davis Superfund Program for nearly four decades.
As of July 8, the commentary, “Inflammation Resolution: a Dual-Pronged Approach to Averting Cytokine Storms in COVID-19?”—the work of a nine-member team of Harvard University and UC Davis researchers—has been downloaded 11,444 times since its publication May 8, 2020. It is online at https://rdcu.be/b33IN.
In comparison, the most downloaded publication in CMR in 2019 received 5,712, statistics show.
Editor-in-Chief and Professor Kenneth Honn, who selected their commentary as the top paper of the month, said it drew more downloads the first week of publication than any other in the journal's history. The work is based on more than 40 years of eicosanoid research from the Hammock lab and more than 40 years of eicosanoid research from the Charles Serhan lab at Harvard Medical School.
“COVID-19 results in excessive inflammation and a cytokine storm caused by the human body's reaction to the SARS-CoV-2 virus,” said lead author Dipak Panigrahy, a Harvard University physician and researcher who collaborates with the Hammock laboratory.
“Controlling the body's inflammatory response to COVID-19 will likely be as important as anti-viral therapies or a vaccine,” Panigraphy said. “Stimulation of inflammation resolutions via pro-resolution lipid mediators that are currently in clinical trials for other inflammatory diseases is a novel approach to turning off the inflammation and preventing the cytokine storm caused by COVID-19.”
The drug is an inhibitor to the soluble epoxide hydrolase (sEH) enzyme, a key regulatory enzyme involved in the metabolism of fatty acids.
Panigraphy and Hammock said they are receiving “tons of calls, media requests and emails” from all over the world, including Norway, Japan, United Kingdom, Germany, France, Mexico and Belgium.
Pioneering research from the Panigrahy and Hammock labs shows that cell debris from surgery, chemotherapy, toxin exposure and other causes lead to production of high levels of pro-inflammatory mediators commonly called cytokines as well as eicosanoids.
“A rapid immune response is critical to controlling this virus,” Panigrahy emphasized.
“We believe it holds promise to combat the inflammation involved with this disease,” said co-author Hammock, a UC Davis distinguished professor who holds a joint appointment with the Department of Entomology and Nematology and the UC Davis Comprehensive Cancer Center. “It hit me in March that what we really need to do is not so much block cytokines as to move upstream to modulate them and resolve them rather than block inflammation.”
“We can increase the concentration of natural pro-resolving mediators termed EETs which act on a biological system to produce other pro-resolution mediators which modulate inflammation and actively resolve the process,” explained Hammock, who founded the Davis-based company EicOsis Human Health LLC, to bring the inhibitor to human clinical trials, which are underway in Texas.
The co-authors include two physician-researchers: Patricia Sime of the Division of Pulmonary and Critical Care Medicine, Virginia Commonwealth University, Richmond, and Irene Cortés-Puch of the Division of Pulmonary, Critical Care and Sleep Medicine, UC Davis Medical Center, and an EicOsis project scientist.
“It is this resolution of inflammation and the subsequent repair that is critical to restore patient health,” said Serhan, whose studies with collaborator Sime show that immune resolution and repair are active processes in the lungs and other tissues. What drives the process, Serhan said, is the production of specific pro-resolving agents (SPMs).
Other co-authors of the paper are Molly Gilligan and Allison Gartung of the Panigrahy lab; Sui Huang of the Institute for Systems Biology, Seattle; and Richard Phipps, independent scholar, Richmond, Va.
National Institutes of Health (NIH) grants, including a National Institute of Environmental Health Science (River Award) to Hammock, helped fund the research. The Panigrahy laboratory is generously supported by the Credit Unions Kids at Heart Team; the C.J. Buckley Pediatric Brain Tumor Fund; and the Joe Andruzzi Foundation.
An enzyme inhibitor developed in the UC Davis laboratory of Bruce Hammock and tested in mice by a team of international researchers shows promise that it could lead to a drug to prevent or reduce the disabilities associated with the neurodevelopmental disorders of autism and schizophrenia.
“We discovered that soluble epoxide hydrolase (sEH) plays a key role in inflammation associated with neurodevelopmental disorders. Inhibiting that enzyme stops the inflammation and the development of autism-like and schizophrenia-like symptoms in animal models,” said collaborator Kenji Hashimoto, a professor with the Chiba University Center for Forensic Mental Health, Japan. The scientists found higher levels of sEH in a key region of the brain—the prefrontal cortex of juvenile offspring-- after maternal immune activation (MIA).
“Mothers who have MIA, which results from severe stress in that region of the brain, have an increased occurrence of neurodevelopment disorders in their offspring,” Hashimoto explained. “In our study, the sEH enzyme increased dramatically in a key brain region of mice pups from mothers with MIA.”
The research, published today (March 18) in the Proceedings of the National Academy of Sciences (PNAS), is the work of 14 researchers from Chiba University Center for Forensic Mental Health; the Laboratory for Molecular Psychiatry, RIKEN Center for Brain Science, in Wako, Saitama, Japan; and the Hammock laboratory.
Research in Mice Pups
By inhibiting sEH, the researchers reversed cognitive and social interaction deficiencies in the mice pups. They hypothesize that this is due to increasing natural chemicals, which prevent brain inflammation. In people, this could reduce the disabilities associated with autism, such as anxiety, gastrointestinal disturbances and epilepsy.
“The same chemical and biochemical markers behaved as predicted in human stem cells,” said Hammock, a distinguished professor who holds a joint appointment with the Department of Entomology and Nematology and the UC Davis Comprehensive Cancer Center.
Earlier studies have indicated a genetic disposition to the disorders. The team also studied postmortem brain samples from autism patients that confirmed the alterations.
“In the case of both autism and schizophrenia, the epidemiology suggests that both genetics and environment are contributing factors,” said neuroscientist and associate professor Amy Ramsey of the Department of Pharmacology and Toxicology, University of Toronto, who was not involved in the study. “In both cases, maternal infection is a risk factor that might tip the scales for a fetus with a genetic vulnerability. This study is important because it shows that their drug can effectively prevent some of the negative outcomes that occur with prenatal infections. While there are many studies that must be done to ensure its safe use in pregnant women, it could mitigate the neurological impacts of infection during pregnancy.”
Neuroscientist Lawrence David, professor and chair of the School of Public Health, University of Albany, N.Y., who was not involved in the research, said that the study might lead to “an important therapeutic intervention for neurodevelopment disorders.”
Might Be Important Therapeutic Invervention
“There is increasing evidence that maternal immune activation activities (MIA) during fetal development can lead to aberrant neurobehaviors, including autistic-like activities,” said Lawrence, who studies neuroimmunology and immunotoxicology. The study “suggests that enzymatic control of fatty acid metabolism is implicated in neuroinflammation associated with schizophrenia and autism spectrum disorders. The expression of Ephx2 giving rise to soluble epoxide hydrolase (sEH) influences production of fatty acid metabolites, which elevate inflammation in the experimental model of mice after MIA; the sEH inhibitor TPPU (N-[1-(1-oxopropyl)-4-piperidinyl]-N'-[4-(trifluoromethoxy)phenyl)-urea) was postnatally used to improved behaviors. Analysis of cadaver brains from individuals with ASD also expressed increased sEH. Fatty acid metabolites have been known to affect fetal development, especially that of the brain; therefore, TPPU might be an important therapeutic intervention for neurodevelopmental disorders.”
Molecular bioscientist Isaac Pessah of the UC Davis School of Veterinary Medicine, distinguished professor and associate dean of research and graduate education in the Department of Molecular Biosciences, described the findings as “significant” and called for more detailed and expanded studies.
“There is mounting evidence that inappropriate maternal immune responses during pregnancy to infection contributes elevated risk to autism spectrum disorder, at least in a fraction of cases,” Pessah said. “The most significant findings reported here is that a commonly used mouse model of immune-triggered behavioral deficits mimicking some of the core symptoms in autistic children can be suppressed by inhibiting a novel biochemical target, soluble epoxide hydrolase; a target not previously explored as a target for therapeutic intervention to treat ASDs. These findings provide a rational basis for more detailed and expanded studies in mice carrying mutations implicated in ASDs to determine whether the therapeutic benefits of soluble epoxide hydrolase inhibitor(s) observed in this study are more generalizable.”
Autism in the United States
The Center for Disease Control and Prevention (CDC) estimates that 1 in 68 children in the United States have autism, commonly diagnosed around age 3. It is four times more common in boys than girls. CDC defines autism spectrum disorder as a “developmental disability that can cause significant social, communication and behavioral challenges.” The disorder impairs the ability to communicate and interact.
Approximately 3.5 million people or 1.2 percent of the population in the United States are diagnosed with schizophrenia, one of the leading causes of disability, according to the Schizophrenia and Related Disorders Alliance of America (SARDAA). Scores more go unreported. Approximately three-quarters of persons with schizophrenia develop the illness between 16 and 25 years of age. Statistics also show that between one-third and one half of all homeless adults have schizophrenia, and 50 percent of people diagnosed have received no treatment. Among the symptoms: delusions, hallucinations, disorganized speech, disorganized or catatonic behavior, and obsessive-compulsive disorders, such as hoarding, according to SARDAA.
Promising Prophylactic or Theraputic Target
In their research paper, titled “Key Role of Soluble Epoxide Hydrolase in the Neurodevelopmental Disorders of Offspring After Maternal Immune Activation,” the scientists described sEH as “a promising prophylactic or therapeutic target for neurodevelopmental disorders in offspring after MIA.”
First author Min Ma and second Qian Ren of the Hashimoto lab conducted the animal and biochemical work, while chemists Jun Yang and Sung Hee Hwang of the Hammock lab performed the chemistry and analytical chemistry. Takeo Yoshikawa, a team leader with the RIKEN's Molecular Psychiatry Laboratory, performed measurements of gene expression in the neurospheres from iPSC (induced pluripotent stem cells) from schizophrenia patients and postmortem brain samples from autism patients.
Hashimoto described the international collaboration as “exciting and productive.” This is their third PNAS paper in a series leading to endoplasmic reticulum stress. “We report discovery of a biochemical axis that leads to multiple neurological disorders, including depression, Parkinson's disease, schizophrenia, autism spectrum disorders and similar diseases,” he said.
First Human Trials
William Schmidt, vice president of clinical development at EicOsis, a Davis-based company developing inhibitors to sEH to treat unmet medical needs in humans and companion animals, said the company is developing a first-in-class therapy for neuropathic and inflammatory pain. “EicOsis is in the process of finalizing our first human trials on the inhibitors of the soluble epoxide hydrolase, originally reported from UC Davis,” Schmidt said. “We are targeting the compounds as opioid replacements to treat peripheral neuropathic pain. It is exciting that the same compound series may be used to prevent or treat diseases of the central nervous system.”
Several grants from the National Institutes of Health, awarded to Hammock, supported the research. Hammock praised the many collaborators and students he has worked with on the project. “This work illustrates the value of research universities in bringing together the diverse talent needed to address complex problems,” Hammock said. “It also illustrates the value of fundamental science. This autism research can be traced directly to the fundamental question of how caterpillars turn into butterflies.”
Now working solely on research to benefit humankind, Hammock began his career in insect science at UC Berkeley where he investigated how epoxide hydrolase degrades a caterpillar's juvenile hormone. The process leads to metamorphosis from the larval stage to the adult insect. Hammock then wondered "Does the enzyme occur in plants? Does it occur in mammals?"
It does, and particularly as a soluble epoxide hydrolase in mammals.
"Science is full of surprises," said Hammock, who founded EicOsis to help human patients conquer pain without opioids. "We need to remember that the concept, the clinical target, and even the chemical structure, came from asking how caterpillars turn into butterflies."
ABSTRACT, PNAS Paper, "Key Role of Soluble Epoxide Hydrolase in the Neurodevelopmental Disorders of Offspring After Maternal Immune Activation"
“Maternal infection during pregnancy increases the risk of neurodevelopmental disorders such as schizophrenia and autism spectrum disorder (ASD) in offspring. In rodents, maternal immune activation (MIA) yields offspring with schizophrenia- and ASD-like behavioral abnormalities. Soluble epoxide hydrolase (sEH) plays a key role in inflammation associated with neurodevelopmental disorders. Here we found higher levels of sEH in the prefrontal cortex (PFC) of juvenile offspring after MIA. Oxylipin analysis showed decreased levels of epoxy-fatty acids in the PFC of juvenile offspring after MIA, supporting increased activity of sEH in the PFC of juvenile offspring. Furthermore, the expression of sEH (or EPHX2) mRNA in iPSC-derived neurospheres from schizophrenia patients with the 22q11.2 deletion was higher than that of healthy controls. Moreover, the expression of EPHX2 mRNA in the postmortem brain samples (Brodmann area 9 and 40) from ASD patients was higher than that of controls. Treatment of TPPU (a potent sEH inhibitor) into juvenile offspring from P28 to P56 could prevent cognitive deficits and loss of parvalbumin (PV)-immunoreactivity in the medial PFC of adult offspring after MIA. In addition, dosing of TPPU to pregnant mothers from E5 to P21 could prevent cognitive deficits, and social interaction deficits and PV-immunoreactivity in the mPFC of juvenile offspring after MIA. These findings suggest that increased activity of sEH in the PFC plays a key role in the etiology of neurodevelopmental disorders in offspring after MIA. Therefore, sEH would represent a promising prophylactic or therapeutic target for neurodevelopmental disorders in offspring after MIA.”
Related Research Published in PNAS
- Soluble Epoxide Hydrolase Plays a Key Role in the Pathogenesis of Parkinson's Disease
- Gene Deficiency and Pharmacological Inhibition of Soluble Epoxide Hydrolase Confers Resilience to Repeated Social Defeat Stress