Morphine‑induced changes in the function of microglia and macrophages after acute spinal cord injury

BMC Neuroscience, 2022 · DOI: https://doi.org/10.1186/s12868-022-00739-3 · Published: September 1, 2022

Simple Explanation

Opioids like morphine are commonly used for pain relief after spinal cord injury (SCI), but they can hinder recovery. This study investigates how morphine affects immune cells (microglia and macrophages) in the spinal cord after injury. The researchers found that morphine increases the number of microglia and macrophages at the injury site and alters their function. This change in immune cell behavior may contribute to the negative effects of morphine on recovery after SCI. Specifically, morphine seems to activate these immune cells, leading to the production of substances that can be harmful to nerve cells. This suggests that using other pain relief methods or combining morphine with drugs that block immune cell activation could improve recovery after SCI.

Study Duration

7 days

Participants

192 Male Sprague Dawley rats

Evidence Level

Not specified

Key Findings

1
Morphine significantly increased the number of microglia and macrophages around the spinal cord lesion after SCI.
2
Morphine increased the expression of both CD86+ and CD206+ cells, indicating changes in the immune cell phenotypes.
3
Repeated morphine administration increased β-arrestin, ERK-1, and dynorphin production by microglia and macrophages, suggesting activation of neurotoxic signaling pathways.

Research Summary

This study investigated the impact of morphine on immune cells (microglia and macrophages) following spinal cord injury (SCI) in rats. The research aimed to understand how morphine affects the inflammatory response and recovery after SCI. The key findings revealed that morphine increases the number of microglia and macrophages at the injury site, alters their phenotypes (CD86+ and CD206+), and promotes the production of factors like β-arrestin, ERK-1, and dynorphin, which are linked to inflammation and cell death. These morphine-induced changes in immune cell function are associated with undermined locomotor recovery and increased hyperalgesia, suggesting that morphine's effects on immune cells contribute to its detrimental impact on SCI recovery.

Practical Implications

Alternative Pain Management

Explore non-opioid pain management strategies to avoid morphine's negative impact on SCI recovery.

Combination Therapies

Investigate combining morphine with drugs that block microglial activation or KORs to mitigate adverse effects.

Personalized Treatment Approaches

Consider individual immune responses when prescribing pain relief after SCI to optimize outcomes.

Study Limitations

1
The study focused exclusively on male rats, limiting generalizability to females.
2
The lack of a neutrophil-specific marker limited differentiation between neutrophils and macrophages.
3
Behavioral and recovery assessments were limited to 7 days post-injury.

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