Information released by researchers discussing newly published research includes the claims that the abdominal pain associated with IBD is caused by bacteria, and infers that the pain is permanent, once triggered. But we know by our own experiences that proper diet changes can stop chronic gut pain. So let’s first look at the research findings about how inflammation initiated by certain bacteria cause activation of pain receptors in the gut. Then we'll discuss how proper diet changes can intervene in this process to reduce or eliminate pain. One of the most frustrating aspects of microscopic colitis is the disconnect between what doctors see and what patients feel. Many MC patients experience severe abdominal cramping, urgency, and pain — yet when a colonoscopy is performed, the inflammation appears mild, or even normal. Physicians often struggle to explain this paradox, and conventional pain medications like NSAIDs (which can worsen MC) or opioids, offer little relief. Two groundbreaking studies from Stanford University and NYU, published in Cell Host & Microbe and PNAS, may have finally solved this puzzle (Lakemeyer, et al., 2025; Teng, Latorre, Bhansali, and Bunnet, 2025).1, 2 The research reveals that a common gut bacterium directly activates pain receptors in the intestine, locking them into a perpetual "on" state. Even more importantly, the findings point toward possibly revolutionary new treatments (how many times have we heard that line before?) — including nanotechnology-based therapies and engineered probiotics — that could provide lasting pain relief without drugs. Discovery #1: A common gut bacterium directly triggers pain. Dr. Matthew Bogyo's team at Stanford discovered that over 50 strains of gut bacteria can activate PAR2 (Protease-Activated Receptor 2), a receptor found on intestinal cells and nerve fibers. When PAR2 is triggered, it generates pain signals, increases intestinal permeability, and drives inflammation. The main culprit was found to be Bacteroides fragilis The most potent pain-triggering bacterium identified was Bacteroides fragilis, which is a common gut microbe that normally behaves benignly, but can become problematic when the intestinal environment is disrupted by:
B. fragilis produces a newly discovered enzyme called BFP1, a protease that:
This is the first direct molecular link between gut microbial imbalance and chronic gut pain. Why does this matters for MC patients? Because this discovery provides a compelling explanation for several mysterious features of microscopic colitis, such as: 1. Pain can be much worse than is indicated by the level of inflammation as seen during a colonoscopy or biopsy analysis. : Many MC patients report severe cramping and urgency even when colonoscopy shows only mild histological changes. The research explains why: pain is being driven by bacterial proteases activating PAR2, not just by visible inflammation. The pain is real, measurable, and has a specific molecular cause—it's not "just in our head." 2. Antibiotic-triggered MC: Post-infectious and antibiotic-associated MC are well-documented. Antibiotics disrupt the gut microbiome, potentially allowing B. fragilis and other protease-producing bacteria to overgrow or behave more aggressively. This could explain why some patients develop MC following antibiotic courses or infections like C. difficile, norovirus, or COVID-19. 3. The leaky gut connection: The research shows that bacterial proteases increase intestinal permeability—the same "leaky gut" mechanism that allows food proteins to enter the bloodstream and trigger food sensitivities in MC. This creates a vicious cycle:
Discovery #2: Pain receptors get "stuck on" inside cells. Dr. Nigel Bunnett's team at NYU discovered why gut pain persists even after flares resolve: PAR2 doesn't shut off after activation. How it works: Normally, cell surface receptors send signals briefly and then deactivate. PAR2 behaves entirely differently:
This explains critical MC phenomena:
This is the first demonstration that intracellular pain signaling drives chronic gut pain. Pain in the gut does not originate inside the epithelial cells themselves, even though PAR2 on epithelial cells is involved in barrier disruption and inflammation. Actual pain signaling comes from sensory neurons (nociceptors) located just beneath the epithelium, but close enough that luminal proteases can reach and activate them. Here’s an anatomical breakdown: 1. Nociceptors (pain-sensing neurons) are located in the lamina propria. These are unmyelinated sensory nerve endings (mostly C-fibers) embedded just below the epithelial surface. Unmyelinated refers to nerve fibers that lack a fatty myelin sheath. They sense:
They're located close enough to the lumen that when the epithelial barrier is disrupted or permeable, bacterial proteases can directly activate PAR2 on these nerve endings. These neurons are the primary source of perceived pain. 2. Colonocytes (the epithelial cells lining the colon) also express PAR2. But these cells do not produce the sensation of pain. Instead, PAR2 on epithelial cells controls:
So epithelial PAR2 worsens inflammation, which then acts on neurons, which generates pain. Think of epithelial PAR2 as the amplifier, not the pain generator. To summarize: Pain is not felt by epithelial cells. It's generated by nociceptor nerve endings — but those nerves are activated by proteases and PAR2 signaling on both neurons and epithelial cells. The epithelial layer is the frontline, the nociceptors just beneath it are the alarm system, and PAR2 is the tripwire. Discovery #3: Nanotechnology can finally stop the pain at its source. Because PAR2 continues signaling inside endosomes where traditional drugs cannot reach, researchers developed nanoparticles that deliver PAR2 blockers directly into endosomes. How the nanoparticles work: These engineered nanoparticles act as "Trojan horses":
Results in animal studies show
This represents a first-in-class pain therapy targeting intracellular receptors—a completely new approach to managing gut pain. What this could mean for MC treatment: If this nanotechnology translates successfully to human trials, MC patients could have access to:
This could be transformative for the approximately 40% of MC patients who struggle to achieve stable remission with current medications. Discovery #4: The gut's microscopic "arms race": A Stunning additional finding: Bogyo's team discovered that gut bacteria engage in a molecular arms race:
This opens the door to next-generation probiotic therapies. Will there be effective future probiotic treatments for MC? Researchers are now exploring engineered probiotics that secrete PAR2-deactivating enzymes. If successful, such probiotics could:
This aligns perfectly with existing MC treatment approaches that emphasize specific probiotic strains like Bifidobacterium infantis 35624, Lactobacillus plantarum 299v, and Saccharomyces boulardii. The mast cell connection: This research may also explain the mast cell involvement in MC. PAR2 activation:
This provides additional mechanistic support for antihistamine and mast-cell stabilizer therapies in MC, including:
The bacterial protease-PAR2-mast cell pathway essentially amplifies inflammation. Current medical treatments do not address the root cause: Budesonide suppresses inflammation and mast cells but doesn't address:
But note that: These findings do not demonstrate that gut pain, once initiated, is "locked on" simply because PAR2 activation becomes "stuck on". It's more complicated than that, as you will see below. Proper diet changes can stop the inflammation caused by PAR2 activation. This was not part of the original studies cited above, of course, since the studies were designed to promote the development of an expensive medication (or drug) to be used for resolving gut pain. But as most of us are aware, the elimination of inflammatory foods from the diet can restore not only proper digestion, but microbiome balance. And most importantly, it can stop the pain associated with MC. The fact that the PAR2 recepters get “stuck on” is irrelevant if the inflammation that is causing the activation of those receptors is suppressed, and this can be done by making the proper diet changes to eliminate the inflammation. After that, the pain cycle will naturally stop. The sensory nerve endings that are responsible for sensing pain in the gut are called nociceptors, and they're a major target for the drugs discussed by the researchers. Endosomes in nociceptors typically last a few hours, up to maybe 24 hours. The descriptions in some of the articles discussing this research leave the impression that the endosomes last much longer, since the pain signaling they produce is "stuck on". But that interpretation is misleading, because sustained endosomal signaling is necessary for prolonged pain signals, and the only way that the signaling can last for extended periods (days, or longer) is if the endosomes are continually replaced as they cycle out, and this requires that the bacteria must continue to produce the protease that activates the PAR2 receptors. If the inflammation cycle that triggers the gut pain can be broken by an anti-inflammatory diet, for example, then the prolonged signaling by the PAR2 receptors will dissipate as the inflammation level declines in response to the diet changes. This tempers the claims made in "Discovery number 2" described above. Although the PAR2 pain receptors may get "stuck on", as stated by Dr. Nigel Bunnett's team in their research findings — in the long run, this is irrelevant. If they were actually "stuck on" for the long-term, an elimination diet could not eliminate the pain symptoms of MC. To the contrary, a safe diet apparently results in the reduction of bacterial protease production, and lower PAR2 activation, because a safe diet can eliminate not only all the clinical symptoms of MC, but it will eventually restore normal histology to the cells of the colonic epithelia. The key distinction is this: A safe diet does not directly “switch off PAR2 receptors”, — it removes the foods and conditions that cause PAR2 activation — which indirectly leads to PAR2 downregulation and mucosal healing (despite the researchers insinuations that the receptors become "stuck on" for the long-term. So diet is fully capable of normalizing these pathways for the following reasons: 1. The gut microbiome is primarily determined by diet. This is one of the strongest findings in all of gut science. The foods you eat determine which bacterial species survive. Removing inflammatory foods changes the ecological environment. Microbiome shifts occur within 48–72 hours after dietary change. 2. Bacterial protease production depends on which bacteria are present. Bacterial serine proteases (the molecules that activate PAR2) are produced by specific species, such as:
When our diet removes the substrate that supports these organisms (certain proteins, emulsifiers, carbohydrates, and additives, for example), their population drops dramatically, and there will be:
Diet changes the species. Species change the proteases. And proteases change the inflammation. 3. The epithelial cells in the colon's lining are replaced very rapidly, with the entire lining being replaced approximately every 3 to 5 days. That ensures that any cells containing "stuck on" PAR2 will be destroyed, and replaced by new cells every 3 to 5 days. Therefore, as the diet changes reduce the general inflammation level in the colon, the newly replaced cells will be less and less likely to be injected with PAR2, so that the inflammation level will eventually return to normal, and any pain associated with the inflammation will dissipate. That said, the reason that MC and other IBD's are chronic, is because the healing process is corrupted. The first stage of the healing process is inflammation. With IBD's, the healing process is stuck on the first stage, because the inflammation is constantly being regenerated (with almost every meal). But once the diet is modified to remove the inflammatory foods, healing can become "unstuck" and proceed normally. References: 1. Lakemeyer, M., Latorre, R., Blazkova, K., Lomax, A. E., Bunnett, N. W., and Bogyo, M. (2025). A Bacteroides fragilis protease activates host PAR2 to induce intestinal pain and inflammation. Cell Host & Microbe, 33(10), pp 1686–1702. e11. Retrieved from https://www.cell.com/cell-host-microbe/abstract/ 2. Teng, S. L., Latorre, R., Bhansali, D., and Bunnet, N. W. (2025). Nanomedicines targeting protease-activated receptor 2 in endosomes provide sustained analgesia. PNAS, 122(41). e2412687122 Retrieved from https://www.pnas.org/doi/10.1073/pnas.2412687122
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