BDNF contributes to IBS-like colonic hypersensitivity via activating the enteroglia-nerve unit
Authors: Fei-Xue Chen
Yan-Bo Yu
Xiao-Di Tan
Peng Wang
Xiu-Li Zuo
Chang-Qing Li
Yan-Qing Li
Suhail Akhtar
Ting Han
Chao Du
Journal: Scientific Reports (2016)
Discipline: Multidisciplinary
Keywords: colonic brain-derived neurotrophic factor (BDNF); abdominal pain; irritable bowel syndrome (IBS); enteroglial cells (EGCs); enteric nerves
Affiliations: Department of Gastroenterology, Qilu Hospital, Shandong University, Jinan 250012, P. R. China., Laboratory of Translational Gastroenterology, Qilu Hospital, Shandong University, Jinan 250012, P. R. China., Department of Physiology, Shandong University School of Medicine, Jinan 250012, P. R. China., Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.

Abstract:  The over-expressed colonic brain-derived neurotrophic factor (BDNF) has been reported to be associated with abdominal pain in patients with irritable bowel syndrome (IBS). However, the neuropathological mechanism is unclear. We here investigated the involvement of enteroglial cells (EGCs) and enteric nerves in IBS-like visceral hypersensitivity. We showed that glial fibrillary acidic protein (GFAP), tyrosine receptor kinase B (TrkB) and substance P (SP) were significantly increased in the colonic mucosa of IBS patients. The upregulation of those proteins was also observed in the colon of mice with visceral hypersensitivity, but not in the colon of BDNF(+/-) mice. Functionally, TrkB or EGC inhibitors, or BDNF knockdown significantly suppressed visceral hypersensitivity in mice. Using the EGC cell line, we found that recombinant human BDNF (r-HuBDNF) could directly activate EGCs via the TrkB-phospholipase CŒ≥1 pathway, thereby inducing a significant upregulation of SP. Moreover, supernatants from r-HuBDNF-activated EGC culture medium, rather than r-HuBDNF alone, triggered markedly augmented discharges in isolated intestinal mesenteric afferent nerves. r-HuBDNF alone could cause mesenteric afferent mechanical hypersensitivity independently, and this effect was synergistically enhanced by activated EGCs. We conclude that EGC-enteric nerve unit may be involved in IBS-like visceral hypersensitivity, and this process is likely initiated by BDNF-TrkB pathway activation. 

Retracted: No

PubPeer comments:
 Figure 3H appears to have two sets of images which overlap. This appears to extend through both rows of images. ***  , 
 Just by looking at the distribution and shape of the labeled immunoreactive elements, it doesn t look like a successful staining but artifact. GFAP-cells should look like star-shaped cells and SP should be seen in long varicose axons. Here, all we can see fluorescent blobs. The degree of colocalization between GFAP and SP is also just too perfect. , 
 Thank you very much for pointing out our mistake. We found in Figure 3H, the figures for the control group (BDNF+ + mice) were mistakenly selected from the candidate representative images for IBS-D FSN group (BDNF+ + mice). We have contacted the editorial office to make an erratum. Your comments are very valuable for us, and we will learn carefully from them to improve our work in future studies. , 
 #3 Thank you for responding. As you seem to have identified the correct data and prepared the correction, would you be so kind as to share it here? , 
 Thank you for your reply. The correction was published online several months ago. Please see details on: https: doi.org 10.1038 s41598-021-98826-8 Thanks again for helping us improve our work. Kind regards! , 
 #5 Thank you. I misunderstood your earlier reply. , 
 #2 yes, I agree. Especially in Figure 2, it is weird to see GFAP, a cytoskeleton protein, being so perfectly colocalized with SP, a secreted peptide. Immunohistochemical controls are needed. , 
 Thank you for your comments. There was no previous report describing the relationship between substance P (SP) and enteric glia (GFAP as a marker), so there were no sufficient data to tell us what double-labeled staining for GFAP and SP looks like. However, we found some single-labeled stain for SP or GFAP in intestine published by others (Gut 2008;57:923u2013929. doi:10.1136 gut.2007.138982; Gastrointestinal and Liver Physiology 307, G1002-12 (2014). doi:10.1152 ajpgi.00164.2014; GLIA 2015;63:921 DOI: 10.1002 glia.22795). Thus, we followed the method for staining the SP and GFAP in intestine. We can see similar signals (long or short trips, or blobs) surrounding the intestinal glands as compared with our figures. Unlike under a monoclonal cell culture environment, it may be not common to stain an enteric glial cell (EGC) to a star-shape, especially within the colonic mucosa because the environment in colon is so complicated that there are many other cells and connective tissue influencing the EGC morphology and activity. Because the fibers of EGC were the majority structure of cell, the staining usually shows thin and long- or short-strip signals in the figures. Furthermore, the fibers exist in a 3-D space, and if the fiber direction is perpendicular to the cut surface, we can only see fluorescent blobs in a 2-D view. Our work showed EGC can express SP under some stimulation, so the colocalization between GFAP and SP staining is explainable. Besides, the high colocalization between GFAP and SP may be caused by our stimulation with control or IBS fecal supernatant, because when we blocked EGC activity with fluorocitrate, the signals for SP was significantly reduced compared with GFAP signals. Furthermore, if we check carefully, the colocalization between GFAP and SP was not completely overlap, especially when the EGC activity was inhibited (Please see Figure 4B of our paper). Comparison of GFAP and SP signals in our paper:  After a careful check of our data, we are sure that the questioned figures presented in the paper were original ones without any improper cropping or manipulation. We have send all original figures to the editorial office and passed through the check before the erratum was published. We deeply thank you for helping us improve our work. Kind regards! ,