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
The paper, which indicates that a brain enzyme could play a key role in curbing or preventing the progression of Parkinson's disease, is one of four singled out as exemplary on the NIEHS website.
“This could be a “revolutionary paper that could cure Parkinson's disease,” commented co-author Bruce Hammock, a UC Davis distinguished professor of entomology with a joint appointment with the UC Davis Comprehensive Cancer Center. He is the 30-year director of the UC Davis NIEHS Superfund Program, which helped fund the research. "A related compound to the drug used in the paper will enter human safety trials sponsored by NIH in early 2019."
The team of 14 scientists demonstrated that inhibiting the enzyme soluble epoxide hydrolase (sEH) compound in mice helped curb the inflammation associated with the development and progression of Parkinson's disease (PD), an age-related brain disorder that affects a million Americans, mostly 60 and over.
The researchers exposed mice to methyl-4-phenyl-1, 2, 3, 6 tetrahydropyridine (MPTP), a neurotoxicant that leads to symptoms of PD in animals. They found two approaches that protected against MPTP-induced neurotoxicity in the mouse brain--adding a potent sEH inhibitor, and genetically modifying mice to not produce sEH.
“Our research suggests that the sEH inhibitor may prevent the progression of Parkinson's disease (PD) as well as treat patients with dementia of Lewy bodies (DLB) if the sEH inhibitor is used in early phases of patients with these disorders,” said Hashimoto, whose career spans 30 years in the development of blood biomarkers and novel therapeutic drugs and includes more than 550 publications on the topic. “Both PD and DLB are chronic and progressive movement disorders. However, the precise causes of these diseases are largely unknown.” Lead author was Qian Ren of the Hashimoto lab.
Hammock and a colleague Sarjeet Gill (now of UC Riverside) discovered the sEH enzyme in a UC Berkeley lab while they were researching insect developmental biology and green insecticides. The work, begun in 1969, led to the discovery that many regulatory molecules are controlled as much by degradation as by biosynthesis, Hammock said. These epoxy fatty acid chemical mediators control blood pressure, fibrosis, immunity, tissue growth, and pain and inflammation.
The Hammock laboratory has published nearly 900 peer-reviewed papers on the sEH enzyme. To date, journals have published more than 17,000 peer-reviewed papers on the sEH enzyme and its inhibitors. Hammock credits the NIEHS with supporting his research in this area since the 1970s.
A Davis-based company, EicOsis, is developing inhibitors to sEH to treat unmet medical needs in humans and animals. The company recently received a multi-million dollar grant from the NIH/NINDS Blueprint Program to move sEH inhibitors through phase I human clinical trials. "We are developing a non-opiate analgesic to treat the chronic pain often associated with diabetes,” said William Schmidt, vice president of clinical development at EicOsis. “Once we have investigational new drug status from the Food and Drug Administration and have finished our phase I trial, physicians will be able initiate their own trials with the EicOsis compound on Parkinson's disease and other Lewy body disorders.”
Hammock said the soluble epoxide hydrolase inhibitors that inhibit the soluble epoxide hydrolase will soon enter human clinical trials supported by the NIH-NINDS Blueprint Program (NIH's Health's National Institute of Neurological Disorders and Stroke). “These drugs could provide relief for patients with a wide variety of inflammatory diseases,” said Hammock, who is a member of the National Academy of Sciences and the National Academy of Inventors.
A newly published study by a team of scientists at Chiba University, Japan and at the University of California, Davis shows that inhibiting an enzyme, the soluble epoxide hydrolase (sEH), plays a key role in curbing the inflammation associated with the development and progression of Parkinson's disease, an age-related brain disorder that affects a million Americans, mostly 60 and over.
The research, published today in the Proceedings of the National Academy of Sciences, is primarily the work of scientists in the labs of Kenji Hashimoto, a professor with the Division of Clinical Neuroscience, Chiba University Center for Forensic Mental Health, Chiba, Japan, and Bruce Hammock, UC Davis distinguished professor of entomology with a joint appointment in the UC Davis Comprehensive Cancer Center.
“Our research suggests that the sEH inhibitor may prevent the progression of Parkinson's disease (PD) as well as treat patients with dementia of Lewy bodies (DLB) if the sEH inhibitor is used in early phases of patients with these disorders,” said Hashimoto, whose career spans 30 years in the development of blood biomarkers and novel therapeutic drugs and includes more than 550 publications on the topic. “Both PD and DLB are chronic and progressive movement disorders. However, the precise causes of these diseases are largely unknown.”
Statistics indicate physicians diagnose 60,000 new cases of Parkinson's disease every year in the United States. The average age of onset is 60, and is more predominant among men.
Hammock said that the work by lead author Qian Ren and his colleagues in the Hashimoto lab “shows that markers and symptoms of Parkinson's disease in whole mice and in human cells with a mutation associated with Parkinson's disease can be treated with a small druglike molecule. By establishing this causal chain of events leading to Lewy body disorders we can better predict environmental chemicals that could predispose people to Parkinson's disease and possibly even treat the disease.”
The paper, titled “Soluble Epoxide Hydrolase Plays a Key Role in the Pathogenesis of Parkinson's Disease,” is co-authored by 14 scientists, including Professor Hammock and Jun Yang and Sung Hee Hwang, all part of the UC Davis Department of Entomology and Nematology and the UC Davis Comprehensive Cancer Center.
“Although there are many medications available to treat symptoms in PD, these do not prevent the progression of the disease, and, to date, no agent with a disease-modifying or neuroprotective indication for PD has been approved,” said Hashimoto. “Therefore, the development of new drugs possessing disease-modifying and /or neuroprotective properties is critical.”
In research studies involving mice, the scientists found “that sEH plays a key role in the inflammation associated with PD pathogenesis and the mechanisms that lead to the disease,” Hashimoto said. “The sEH inhibitor or deletion of the sEH gene protected against MPTP-induced neurotoxicity in mouse brain.” MPTP is an acronym for methyl-4-phenyl-1, 2, 3, 6 tetrahydropyridine, a relative of cyperquat and paraquat herbicides. “Our findings indicate that sEH inhibitors or epoxy fatty acids mimics may be promising prophylactic or therapeutic drugs for alpha-synuclein-related neurodegenerative disorders.”
Robert Higgins, emeritus professor of neuropathology at the UC Davis School of Veterinary Medicine, said: "I find it exciting that Ren and colleagues illustrate a promising path to a drug to prevent the progression of Parkinson's disease. It is impressive how far this work has come since we collaborated with Shirley Gee and the Hammock laboratory on developing a sheep model of Parkinson's disease in the early 1980s."
Neurosurgeon Cesar Borlongan of Morsani College of Medicine, University of South Florida, who was not involved in the study, praised the findings as advancing “our understanding of how Parkinson's disease evolves.” Describing Parkinson's disease as “a devastating brain disorder that mostly affects the aging population,” he said: “There is no cure, only relief from symptoms which include tremors, muscle rigidity, slurred speech, and freezing of gait.”
“While we know that a certain group of brain cells that produce dopamine are selectively destroyed in Parkinson's patients, what triggers this brain cell death remains poorly understood,” said Borlongan, a distinguished professor and vice chair for Research, Department of Neurosurgery and Brain Repair. “In their paper, the authors observed that a protein called soluble epoxide hydrolase (sEH) may be key to the demise of the brain dopamine cells. In small and large animal models of Parkinson's disease, and further confirmed in a group of PD patients, this protein is highly elevated in specific regions of the brain implicated in dopamine cell death.”
Borlongan pointed out that “Equally compelling evidence demonstrated that using a drug that inhibits sEH can reduce brain inflammation and levels of sEH and effectively lessen PD-associated toxicity in the animal models of the disease. Clinical trials of sEH inhibitors in heart and lung disease have been ongoing over the last decade, and may facilitate the entry of these drugs for PD. These results advance our understanding of how PD may evolve, but also point to its novel treatment.”
Qing Li, a professor in the Department of Molecular Biosciences and Bioengineering, College of Tropical Agriculture and Human Resources, University of Hawaii at Mānoa, who also was not involved in the study, called Parkinson's disease “a devastating neurodegenerative disorder that affects patients and caregivers alike with a significant economic burden in the United States and worldwide.”
This basic research drew support from several grants from Japan, including the Strategic Research Program for Brain Sciences, and at UC Davis, grants funded by the National Institute of Health's Institute of Environmental Health Sciences (NIH/NIEHS), and the NIEHS Superfund Program.
Hammock, a member of the National Academy of Sciences and the National Academy of Inventors, has directed the NIH/NIEH Superfund Program for more than 30 years.
Hammock said the soluble epoxide hydrolase inhibitors that inhibit the soluble epoxide hydrolase will soon enter human clinical trials supported by the NIH-NINDS Blueprint Program (NIH's Health's National Institute of Neurological Disorders and Stroke). “These drugs could provide relief for patients with a wide variety of inflammatory diseases,” he said.
The Hammock laboratory has published nearly 900 peer-reviewed papers on the sEH enzyme, discovered while Hammock and Sarjeet Gill (now of UC Riverside) were researching insect developmental biology and green insecticides at UC Berkeley. The work, begun in 1969, led to the discovery that many regulatory molecules are controlled as much by degradation as by biosynthesis, Hammock said. These epoxy fatty acid chemical mediators control blood pressure, fibrosis, immunity, tissue growth, and pain and inflammation.
To date, journals have published more than 17,000 peer-reviewed papers on the sEH enzyme and its inhibitors. Hammock credits the NIEHS for supporting his research in this area since the 1970s.
A Davis-based company, EicOsis, is developing inhibitors to sEH
to treat unmet medical needs in humans and animals. The company recently received a multi-million dollar grant from the NIH/NINDS Blueprint Program to move sEH inhibitors through phase I human clinical trials. “We are developing a non-opiate analgesic to treat the chronic pain often associated with diabetes,” said William Schmidt, vice president of clinical development at EicOsis. “Once we have investigational new drug status from the Food and Drug Administration and have finished our phase I trial, physicians will be able initiate their own trials with the EicOsis compound on Parkinson's disease and other Lewy body disorders.”
The research, published March 14 in the journal Proceedings of the National Academy of Sciences, involves studies of an inhibitor of soluble epoxide hydrolase in rodents. Soluble epoxide hydrolase, or sEH, is emerging as a therapeutic target that acts on a number of inflammatory or inflammation-linked diseases.
“The research in animal models of depression suggests that sEH plays a key role in modulating inflammation, which is involved in depression,” said Hammock, a distinguished professor of entomology with a joint appointment at the UC Davis Comprehensive Cancer Center. “Inhibitors of sEH protect natural lipids in the brain that reduce inflammation, and neuropathic pain. Thus, these inhibitors could be potential therapeutic drugs for depression.”
They found that TPPU displayed rapid effects in both inflammation and social defeat-stress models of depression. Expression of sEH protein was higher in key brain regions of chronically stressed mice was higher than in control mice, they found.
“Most drugs for psychiatric diseases target how neurons communicate; here we are targeting the wellness and environment of the neurons,” said UC Davis researcher Christophe Morisseau.
The researchers also discovered that postmortem brain samples of patients with psychiatric diseases, including depression, bipolar disorder, and schizophrenia, showed a higher expression of sEH than controls.
The researchers found that pretreatment with TPPU prevented the onset of depression-like behaviors in mice after induced inflammation or repeated social-defeat stress. Mice lacking the sEH gene did not show depression-like behavior after repeated social-defeat stress.
“All these findings suggest that sEH plays a key role in the pathophysiology of depression and that epoxyfatty acids, and their mimics as well as sEH inhibitors, are potential therapeutic or prophylactic drugs for depression,” Hashimoto said.
Robert E. Hales, distinguished professor of clinical psychiatry and the Joe P. Tupin Endowed Chair of the Department of Psychiatry and Behavioral Sciences at UC Davis School of Medicine, said new medication treatment approaches are needed to treat depression. Hales, who was not involved in the research, said the new paper represents “an important and novel approach to treating depression.”
“With lifetime prevalence rates of major depressive disorder being in the range of 16 percent and with nearly two-thirds of patients failing to respond to pharmacologic treatments, there is a pressing need to discover new medication treatment approaches,” Hales said. “Their findings lend support to the potential use of TPPU, a sEH inhibitor, as a new therapeutic medication to prevent and treat depression.”
Other authors on the paper are: Qian Ren, Min Ma, Tamaki Ishima, Ji-chun Zhang, Chun Yang, Wei Yao, Chao Dong, and Mei Han, Chiba University; and Jun Yang at UC Davis.
Morisseau, Yang and Wagner are inventors on University of California patents related to soluble epoxide hydrolase. Some of these patents have been licensed by EicOsis Human Health, a Davis company founded by Hammock to develop pharmaceuticals to alleviate neuropathic and inflammatory pain.
The research was funded by Grant-in-Aid for Scientific Research on Innovative Areas of the Ministry of Education, Culture, Sports, Science and Technology, Japan to Kenji Hashimoto, (#24116006), and a Research Fellowship for Young Scientists of the Japan Society for the Promotion of Science (Tokyo, Japan) to Qian Ren.
Partial support was provided by the National Institute of Environmental Health Sciences (NIEHS) R01 ES002710, NIEHS Superfund Research Program grant P42 ES004699, and NIH U24 DK097154 West Coast Comprehensive Metabolomics Center.
Hammock and Professor Bruce German, UC Davis recently received a National Institutes of Health grant in collaboration with Pei-an Shih, UC San Diego Department of Psychiatry, to investigate the role of bioactive lipids in a related psychiatric disorder, anorexia nervosa.