Inflammation, Anti-inflammation and Chronic Inflammation
The inflammatory reaction to injury is complex, involving a massive response from the immune cells that guard and protect the body. These include fibroblasts in the local tissue, lymphocytes in lymph nodes and several other cells circulating in blood vessels. With injury to local tissue the smallest blood vessels in the area, capillaries, move cells into the tissue. These cells release inflammatory chemicals that attack damaged tissue and attract more cells from the capillaries. Fibroblasts are called into action and contribute to this inflammatory sequence that methodically destroys and devours damaged tissue. This battle that is mounted in our connective tissue system sends pain signals to the brain, where pain is perceived. That pain causes us to stop using that part of the body to allow it to finish the inflammatory activity.
Once the tissue is cleaned up, the anti-inflammatory response starts. It has its own sequence of events, starting with the release of chemicals that block current inflammatory chemicals and moving to a completely separate cascade that actively promotes anti-inflammation. This anti-inflammatory cascade leads to the return of normal maintenance and repair function of fibroblasts and guarding function of lymphocytes and other immune cells. Pain decreases and the brain sends instructions to restore normal use of this area.
In chronic inflammation several things happen to change all of this. Most importantly, the brain responds to pain signaling and ramps up pain from its normal state to excessive and persistent pain. Instead of using built in mechanisms to suppress pain, it uses neuroplastic processes to wind up and maintain it, even if local tissue damage in the body is repaired. These processes cause the brain’s own immune cells to release inflammatory chemicals, instructing wildly firing nerve cells in the pain pathway to release more of the main pain neurotransmitter, Substance-P. This expands the pain map and we perceive more pain. It also expands the loop between brain and body by sending much of that excess Substance-P down nerves into the peripheral body. Here, it is released into the already inflamed tissue, completely overwhelming the ability of the local tissue to block the inflammatory cascade and mount the anti-inflammatory process. Thus inflammation in local tissue goes on, regardless of whether or not the initial injury is resolved