An acute inflammatory response to the use of granulocyte colony-stimulating factor to prevent infections in patients with brain injury: what about the brain?

Contributions of the immune system to the pathophysiology of traumatic brain injury - evidence by intravital microscopy

Traumatic brain injury (TBI) results in immediate brain damage that is caused by the mechanical impact and is non-reversible. This initiates a cascade of delayed processes which cause additional—secondary—brain damage. Among these secondary mechanisms, the inflammatory response is believed to play an important role, mediating actions that can have both protective and detrimental effects on the progression of secondary brain damage. Histological data generated extensive information; however, this is only a snapshot of processes that are, in fact, very dynamic. In contrast, in vivo microscopy provides detailed insight into the temporal and spatial patterns of cellular dynamics. In this review, we aim to summarize data which was generated by in vivo microscopy, specifically investigating the immune response following brain trauma, and its potential effects on secondary brain damage.

Enhanced pulmonary inflammation following experimental intracerebral hemorrhage

The association between brain damage and respiratory dysfunction has been recognized although mechanistic link between the two is still poorly defined. Intracerebral hemorrhage is accompanied by brain injury, stroke, and parenchymal hematoma formation with surrounding inflammation. Increase intracranial pressure as a result of intracerebral hemorrhage may promote localized activation of cytokines and coagulation system including tissue factor release. However, whether intracerebral hemorrhage triggers inflammation in noncerebral organs has not been elucidated. The aim of the present study was to examine the impact of intracerebral hemorrhage on lung inflammatory response. Intracerebral hemorrhage was induced by stereotaxic intrastriatal administration of bacterial collagenase. Expression of intracellular adhesion molecule-1 (ICAM-1), IKB-alpha, tissue factor, tumor necrosis factor-alpha (TNF-alpha), and interleukin-1beta (IL-1beta) was evaluated by Western blot analysis. Our results revealed that intracerebral hemorrhage upregulated expression of ICAM-1 and tissue factor in both brain and lung, whereas it enhanced TNF-alpha and IL-1beta mainly in brain within 6 and 24 h of the brain injury. Levels of IKB-alpha remained unchanged in brain and lung tissues. Appearance of inflammatory markers in the lung was accompanied by morphological pulmonary damage. These data suggest that intracerebral hemorrhage may trigger acute inflammatory response in both brain and lung.

Effect of granulocyte colony-stimulating factor on functional and histopathologic outcome after traumatic brain injury in mice

OBJECTIVE

Granulocyte colony-stimulating factor has been used to reduce the risk of sepsis in patients with traumatic brain injury. However, granulocyte colony-stimulating factor exerts potent pro- and anti-inflammatory effects that could influence secondary injury, and outcome, after traumatic brain injury. Our objective was to determine the effect of granulocyte colony-stimulating factor on histopathologic, motor, and cognitive outcome after experimental traumatic brain injury in mice.

DESIGN

Experimental study.

SETTING

Research laboratory at the Massachusetts General Hospital, Boston, MA.

SUBJECTS

Forty-eight adult male C57Bl/6 mice.

INTERVENTIONS

Mice (8 wks of age, n = 16/group) were administered granulocyte colony-stimulating factor or saline subcutaneously twice per day for 7 days after controlled cortical impact or sham injury (n = 16). Absolute neutrophil counts, motor function, Morris water maze performance, and lesion volume were determined after controlled cortical impact or sham injury.

MEASUREMENTS AND MAIN RESULTS

At the time of controlled cortical impact, body weight, brain and body temperature, and systemic absolute neutrophil counts did not differ between groups. Compared with control, systemic absolute neutrophil count was increased more than ten-fold in granulocyte colony-stimulating factor-treated mice on posttrauma days 2 and 7 (p < .05, repeated-measures analysis of variance) but did not differ between groups by day 14. There were no differences between groups in tests of motor function or histopathologic outcome. However, compared with control, mice given granulocyte colony-stimulating factor had improved Morris water maze performance after controlled cortical impact (p < .05, repeated-measures analysis of variance) but not sham injury.

CONCLUSIONS

The data suggest a small beneficial effect of granulocyte colony-stimulating factor on functional outcome after traumatic brain injury in adult mice but do not show differences in histopathology or motor outcome between treated and control groups.

Nosocomial infections and immunity: lesson from brain-injured patients

Of brain-injured patients admitted to intensive care units, a significant number acquires nosocomial infections. Increased susceptibility to infectious agents could, at least partly, be due to transient immunodepression triggered by brain damage. Immune deficiency in patients with severe brain injury primarily involves T cell dysfunction. However, humoral and phagocytic deficiencies are also detectable. Activation of the hypothalamo-pituitary-adrenal axis and the sympathetic nervous system plays a crucial role in brain-mediated immunodepression. In this review we discuss the role of immunodepression in the development of nosocomial infections and clinical trials on immunomodulation in brain-injured patients with hospital-acquired infections.

Cognitive dysfunction and chemotherapy: neuropsychological findings in perspective

Currently, the interest in cognitive functioning following chemotherapy is rapidly expanding as is reflected in a growing number of published studies on this topic. Although most studies are indicative of cognitive deficits after chemotherapy, definite conclusions on the role of chemotherapy on cognitive function can often not be drawn due to methodological problems. On the basis of the studies on cognitive functioning after chemotherapy that are conducted in The Netherlands Cancer Institute, the current article describes a number of such methodological topics that obscure straightforward interpretation of neuropsychological findings in toxicity research. Measurement issues that diverge from usual assessment issues encountered in psychosocial oncology will be described, and factors that might play a role in the cause of cognitive impairment will be evaluated. Also, future developments necessary to gain more insight into the prevalence, the pattern, and the impact of cognitive problems following chemotherapy are discussed