Long-term survival and five year hospital resource usage following traumatic brain injury in Scotland from 1997 to 2015: A population-based retrospective cohort study

Heme: The Lord of the Iron Ring

Heme is an iron-protoporphyrin complex with an essential physiologic function for all cells, especially for those in which heme is a key prosthetic group of proteins such as hemoglobin, myoglobin, and cytochromes of the mitochondria. However, it is also known that heme can participate in pro-oxidant and pro-inflammatory responses, leading to cytotoxicity in various tissues and organs such as the kidney, brain, heart, liver, and in immune cells. Indeed, heme, released as a result of tissue damage, can stimulate local and remote inflammatory reactions. These can initiate innate immune responses that, if left uncontrolled, can compound primary injuries and promote organ failure. In contrast, a cadre of heme receptors are arrayed on the plasma membrane that is designed either for heme import into the cell, or for the purpose of activating specific signaling pathways. Thus, free heme can serve either as a deleterious molecule, or one that can traffic and initiate highly specific cellular responses that are teleologically important for survival. Herein, we review heme metabolism and signaling pathways, including heme synthesis, degradation, and scavenging. We will focus on trauma and inflammatory diseases, including traumatic brain injury, trauma-related sepsis, cancer, and cardiovascular diseases where current work suggests that heme may be most important.

Activation of Nrf2 to Optimise Immune Responses to Intracerebral Haemorrhage

Haemorrhage into the brain parenchyma can be devastating. This manifests as spontaneous intracerebral haemorrhage (ICH) after head trauma, and in the context of vascular dementia. Randomised controlled trials have not reliably shown that haemostatic treatments aimed at limiting ICH haematoma expansion and surgical approaches to reducing haematoma volume are effective. Consequently, treatments to modulate the pathophysiological responses to ICH, which may cause secondary brain injury, are appealing. Following ICH, microglia and monocyte derived cells are recruited to the peri-haematomal environment where they phagocytose haematoma breakdown products and secrete inflammatory cytokines, which may trigger both protective and harmful responses. The transcription factor Nrf2, is activated by oxidative stress, is highly expressed by central nervous system microglia and macroglia. When active, Nrf2 induces a transcriptional programme characterised by increased expression of antioxidant, haem and heavy metal detoxification and proteostasis genes, as well as suppression of proinflammatory factors. Therefore, Nrf2 activation may facilitate adaptive-protective immune cell responses to ICH by boosting resistance to oxidative stress and heavy metal toxicity, whilst limiting harmful inflammatory signalling, which can contribute to further blood brain barrier dysfunction and cerebral oedema. In this review, we consider the responses of immune cells to ICH and how these might be modulated by Nrf2 activation. Finally, we propose potential therapeutic strategies to harness Nrf2 to improve the outcomes of patients with ICH.

Healthcare Utilization Following Traumatic Brain Injury in a Large National Sample

OBJECTIVE

To evaluate the impact of traumatic brain injury (TBI) on healthcare utilization (HCU) over a 1-year period in a large national sample of individuals diagnosed with TBI across multiple care settings.

SETTING

Commercial insurance enrollees.

PARTICIPANTS

Individuals with and without TBI, 2008-2014.

DESIGN

Retrospective cohort.

MAIN MEASURES

We compared the change in the 12-month sum of inpatient, outpatient, emergency department (ED), and prescription HCU from pre-TBI to post-TBI to the same change among a non-TBI control group. Most rehabilitation visits were not included. We stratified models by age ≥65 and included the month of TBI in subanalysis.

RESULTS

There were 207 354 individuals in the TBI cohort and 414 708 individuals in the non-TBI cohort. Excluding the month of TBI diagnosis, TBI resulted in a slight increase in outpatient visits (rate ratio [RtR] = 1.05; 95% confidence interval [CI], 1.04-1.06) but decrease in inpatient HCU (RtR = 0.86; 95% CI, 0.84-0.88). Including the month of TBI in the models resulted in increased inpatient (RtR = 1.55; 95% CI, 1.52-1.58) and ED HCU (RtR = 1.37; 95% CI, 1.34-1.40).

CONCLUSION

In this population of individuals who maintained insurance coverage following TBI, results suggest that TBI may have a limited impact on nonrehabilitation HCU at the population level.