Neuroepithelial circuit formed by innervation of sensory enteroendocrine cells.

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2015-02

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Abstract

Satiety and other core physiological functions are modulated by sensory signals arising from the surface of the gut. Luminal nutrients and bacteria stimulate epithelial biosensors called enteroendocrine cells. Despite being electrically excitable, enteroendocrine cells are generally thought to communicate indirectly with nerves through hormone secretion and not through direct cell-nerve contact. However, we recently uncovered in intestinal enteroendocrine cells a cytoplasmic process that we named neuropod. Here, we determined that neuropods provide a direct connection between enteroendocrine cells and neurons innervating the small intestine and colon. Using cell-specific transgenic mice to study neural circuits, we found that enteroendocrine cells have the necessary elements for neurotransmission, including expression of genes that encode pre-, post-, and transsynaptic proteins. This neuroepithelial circuit was reconstituted in vitro by coculturing single enteroendocrine cells with sensory neurons. We used a monosynaptic rabies virus to define the circuit's functional connectivity in vivo and determined that delivery of this neurotropic virus into the colon lumen resulted in the infection of mucosal nerves through enteroendocrine cells. This neuroepithelial circuit can serve as both a sensory conduit for food and gut microbes to interact with the nervous system and a portal for viruses to enter the enteric and central nervous systems.

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10.1172/JCI78361

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Bohórquez, DV, RA Shahid, A Erdmann, AM Kreger, Y Wang, N Calakos, F Wang, RA Liddle, et al. (2015). Neuroepithelial circuit formed by innervation of sensory enteroendocrine cells. J Clin Invest, 125(2). pp. 782–786. 10.1172/JCI78361 Retrieved from https://hdl.handle.net/10161/9363.

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Scholars@Duke

Bohorquez

Diego V. Bohorquez

I am a gut-brain neuroscientist.

Though my initial studies focused on GI physiology and nutrition, my expertise evolved to include neuroscience following the many personal stories, which have carefully sharpened my career vision along the way.  While pursuing a Doctoral degree in Nutrition, a friend shared her struggles with obesity and gastric bypass surgery.  

Surgery was a last resort but helped to reduced her body weight dramatically and resolved her diabetes.  Yet, the most striking part of her story for me was that her perception of taste had been markedly transformed. Reshaping her gut caused her brain to convert a prior repulsion at the appearance of runny egg yolk into a strong craving to eat those same eggs.

Today, we are still a long way from understanding the full details of these intriguing conversations between our gut and our brain. But, the more we understand, the closer we are getting to treating disorders involving alterations in the perception of food in our gut.

My focus is to unveil how the brain perceives what the gut feels, how food in the intestine is sensed by our body, and how a sensory signal from a nutrient is transformed into an electrical signal that alters behavior.

Calakos

Nicole Calakos

We all know that as part of our daily lives we are constantly interacting with our environment - learning, adapting, establishing new memories and habits, and for better or for worse, forgetting as well. At the cellular level, these processes can be encoded by changes in the strength of synaptic transmission between neurons. The process by which neuronal connections change in response to experience is known as “synaptic plasticity” and this process is a major interest of our laboratory. Our goals are to understand the molecular mechanisms for synaptic plasticity and identify when these processes have gone awry in neurological diseases. In doing so, we will establish the necessary framework to target these processes for therapeutic interventions; potentially identifying novel and improved treatment options.

We focus these interests on the striatal circuitry of the basal ganglia. The striatum is a key entry point for cortical information into the basal ganglia. The basal ganglia are involved in a wide variety of behaviors because they are critical for our movement, including the learning of motor routines and when to call them into action. Disorders in this process have wide ranging manifestations and substantially contribute to diseases like Parkinson’s disease, OCD, dystonia, Tourette’s and addictive behavior.

Our lab has pioneered a number of molecular and circuit-cracking methodologies that have provided new views into the workings of the striatal circuitry and its plasticity rules. Our lab has deep expertise in electrophysiology and optical physiology (two photon calcium imaging) and state-of-the-art molecular genetic mouse modeling techniques. Yet, our insights are further amplified by the highly collaborative approach we have with colleagues at Duke and beyond.

To get a better view of how pathway balance in basal ganglia circuitry may be affected, our lab has developed tools and approaches that make it possible to study the function of striatal medium spiny neurons in the direct and indirect pathways simultaneously in living tissue (Shuen et al., 2008Ade et al., 2011O’Hare and Ade et al., 2016). We use them to identify functional differences between these two types of medium spiny neurons and their role in normal adaptive plasticity and disease processes.

In habit, we identified circuit predictors of behavior. These include some classic expectations for mechanisms of plasticity such as increased firing activity, but also some surprises, like finding shifts in the timing of firing between these two cell types (O’Hare and Ade et al., 2016) and that a key coordinator is an interneuron (O’Hare et al., eLife 2017).

In disease settings, we leverage the Sapap3 KO model to understand what causes repetitive, self-injurious behavior and anxiety-like behaviors (“OCD-like”). We find a central role for striatal group 1 metabotropic glutamate receptor overactivity (Ade et al., Biol. Psych. 2016). By developing a unique high-throughput screening assay for an inherited cause of the movement disorder, dystonia, we came to recognize that multiple forms of this disease were united by a common defect in signaling by the proteostasis pathway known as the “integrated stress response” or ISR (also eIF2alpha phosphorylation) (Rittiner and Caffall et al., Neuron 2016).

Currently, ISR research in the lab has markedly expanded to address both its basic mechanisms (Helseth and Hernandez-Martinez et al., Science 2021) and its translational potential (Caffall et al., Sci. Transl. Med. 2021) for dystonia, Parkinson’s and other brain diseases.

Wang

Fan Wang

My lab studies neural circuit basis of sensory perception. 
Specifically we are interested in determining neural circuits underlying (1) active touch sensation including tactile processing stream and motor control of touch sensors on the face; (2) pain sensation including both sensory-discriminative and affective aspects of pain; and (3) general anesthesia including the active pain-suppression process. We use a combination of genetic, viral, electrophysiology, and in vivo imaging (in free-moving animals) techniques to study these questions.

Liddle

Rodger Alan Liddle

Our laboratory has two major research interests:

Enteroendocrine Cell Biology

Enteroendocrine cells (EECs) are sensory cells of the gut that send signals throughout the body.  They have the ability to sense food and nutrients in the lumen of the intestine and secrete hormones into the blood.  Our laboratory has had a longstanding interest in two types of EECs that regulate satiety and signal the brain to stop eating.   Cholecystokinin (CCK) is secreted from EECs of the upper small intestine and regulates the ingestion and digestion of food through effects on the stomach, gallbladder, pancreas and brain.  Peptide YY (PYY) is secreted from EECs of the small intestine and colon and regulates satiety.  We recently demonstrated that CCK and PYY cells not only secrete hormones but are directly connected to nerves through unique cellular processes called ‘neuropods’.  Our laboratory is devoted to understanding EECs signaling and its role in disease.

Pancreatitis

Pancreatitis is an inflammatory disease of the pancreas compounded by intrapancreaatic activation of digestive enzymes.  Our laboratory is studying the influence of nerves on the development of pancreatitis. Neurogenic inflammation results from the release of bioactive substances from sensory neurons in the pancreas causing vasodilatation, edema, and inflammatory cell infiltration producing tissue necrosis. Our goal is to identify the agents that activate sensory neurons, characterize the receptors on sensory nerves that mediate these actions, and determine the effects of neural stimulation on pancreatic injury with the long-term objective of developing strategies to reduce neurogenic inflammation to treat pancreatitis. 

Visit our lab page.


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