The information content of an organism is recorded in the DNA of its genome and expressed through transcription. Here, mRNA serves as a transient intermediary molecule in the information network, whilst non-coding RNAs perform additional diverse functions. A transcriptome captures a snapshot in time of the total transcripts present in a cell. Transcriptomics technologies provide a broad account of which cellular processes are active and which are dormant.

A variety of genes are involved in many biological processes, one of which may be involved in a person transitioning between acute (short-term) pain to chronic (ongoing or persistent) pain. Some forms of chronic pain may be a disorder in the way the nervous system and the immune system interact, involving neuroinflammation. In acute pain, immune cells converge on damaged tissue (inflammation) and also influence the nervous system. Once activated, these cells enable the release of substances to temporarily alter the peripheral and the central nervous system, as well as cells adjacent to the damaged area. Support cells in the central nervous system are also activated, and control substances that enhance signal transmission in the spinal cord and brain. Both sets of cells (immune cells and support cells) may be involved in the transition from acute pain to chronic pain.

In this study, the researchers investigated molecular mechanisms in peripheral blood immune cells across the whole human transcriptome, and found that acute inflammatory responses appear to protect against developing chronic pain, in people with low back pain. They repeated the same investigation in people with temporomandibular disorder (jaw joint pain) with similar findings.

The researchers used experimental data from rats to understand how the processes developed over time, and followed up with human data from the UK Biobank to look at the impact of using anti-inflammatory drugs for acute pain on long-term outcomes. They found that those people who used anti-inflammatory drugs reported a 1.76 fold greater risk of developing chronic low back pain (at three months), while those who didn’t use anti-inflammatory drugs recovered. The elevated risk was maintained for up to 7 years.

The number of neutrophils (a type of white blood cell) present in the blood stream differentiated between those who used anti-inflammatory drugs, and those who used other pain relieving medications, antidepressants or did not use any medication. Those who used anti-inflammatory drugs showed lower levels of neutrophils over time.

The authors conclude that, while it’s early in this investigation, short-term activity where the number of neutrophils rises briefly due to inflammation in acute pain is beneficial, while blocking this action by using anti-inflammatory medications appears to delay recovery. The authors argue that it’s important to understand the long-term effects of using anti-inflammatory drugs for acute low back pain, as it may lead to poorer outcomes over time.