Serum haptoglobulin changes in patients with severe isolated head injury

Blood-Related Toxicity after Traumatic Brain Injury: Potential Targets for Neuroprotection

Emergency visits, hospitalizations, and deaths due to traumatic brain injury (TBI) have increased significantly over the past few decades. While the primary early brain trauma is highly deleterious to the brain, the secondary injury post-TBI is postulated to significantly impact mortality. The presence of blood, particularly hemoglobin, and its breakdown products and key binding proteins and receptors modulating their clearance may contribute significantly to toxicity. Heme, hemin, and iron, for example, cause membrane lipid peroxidation, generate reactive oxygen species, and sensitize cells to noxious stimuli resulting in edema, cell death, and increased morbidity and mortality. A wide range of other mechanisms such as the immune system play pivotal roles in mediating secondary injury. Effective scavenging of all of these pro-oxidant and pro-inflammatory metabolites as well as controlling maladaptive immune responses is essential for limiting toxicity and secondary injury. Hemoglobin metabolism is mediated by key molecules such as haptoglobin, heme oxygenase, hemopexin, and ferritin. Genetic variability and dysfunction affecting these pathways (e.g., haptoglobin and heme oxygenase expression) have been implicated in the difference in susceptibility of individual patients to toxicity and may be target pathways for potential therapeutic interventions in TBI. Ongoing collaborative efforts are required to decipher the complexities of blood-related toxicity in TBI with an overarching goal of providing effective treatment options to all patients with TBI.

Age-Dependent Effects of Haptoglobin Deletion in Neurobehavioral and Anatomical Outcomes Following Traumatic Brain Injury

Cerebral hemorrhages are common features of traumatic brain injury (TBI) and their presence is associated with chronic disabilities. Recent clinical and experimental evidence suggests that haptoglobin (Hp), an endogenous hemoglobin-binding protein most abundant in blood plasma, is involved in the intrinsic molecular defensive mechanism, though its role in TBI is poorly understood. The aim of this study was to investigate the effects of Hp deletion on the anatomical and behavioral outcomes in the controlled cortical impact model using wildtype (WT) C57BL/6 mice and genetically modified mice lacking the Hp gene (Hp(-∕-)) in two age cohorts [2-4 mo-old (young adult) and 7-8 mo-old (older adult)]. The data obtained suggest age-dependent significant effects on behavioral and anatomical TBI outcomes and recovery from injury. Moreover, in the adult cohort, neurological deficits in Hp(-∕-) mice at 24 h were significantly improved compared to WT, whereas there were no significant differences in brain pathology between these genotypes. In contrast, in the older adult cohort, Hp(-∕-) mice had significantly larger lesion volumes compared to WT, but neurological deficits were not significantly different. Immunohistochemistry for ionized calcium-binding adapter molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) revealed significant differences in microglial and astrocytic reactivity between Hp(-∕-) and WT in selected brain regions of the adult but not the older adult-aged cohort. In conclusion, the data obtained in the study provide clarification on the age-dependent aspects of the intrinsic defensive mechanisms involving Hp that might be involved in complex pathways differentially affecting acute brain trauma outcomes.

Hypohaptoglobinemia associated with familial epilepsy

In select kindreds afflicted with familial idiopathic epilepsy, most individuals suffering seizures also have low levels of the plasma hemoglobin-binding protein, haptoglobin. This hypohaptoglobinemia may be causally associated with a tendency to develop epilepsy. Our experimental results indicate that artificially-induced hypohaptoglobinemia in mice causes retarded clearance of free hemoglobin from the central nervous system, and that such free hemoglobin may engender the peroxidation of brain lipids. We hypothesize that hypohaptoglobinemia, either inherited, or acquired via traumatic processes, may prevent efficient clearance of interstitial hemoglobin from the central nervous system, thereby predisposing these people to encephalic inflammation and the appearance of seizure disorders.

Predicting lethal outcome after severe head injury -- a computer-assisted analysis of neurological symptoms and laboratory values

A total number of 58 parameters (laboratory values, neurological symptoms, and vegetative parameters) were evaluated in 150 patients during the first seven days after severe head injury. The patients were divided into two groups, "survivors" and "non-survivors". Eight easily evaluable routine parameters with the most significant differences between the two groups of patients were used for statistical evaluation of a "no survival chance score". These highly indicative parameters are serum osmolarity and urea, blood glucose, total bilirubin, motor reaction to stimuli, body temperature, respiratory activity, and pupil reaction. A "low survival chance limit" was evaluated from each of these parameters by computer analysis. None of the patients in the series survived when three or more of these eight parameters had climbed beyond the limit. So far, the system is able to predict "no survival chances" in 50.8% of the non-survivors some six days prior to death; 80% of these predictions could be made by the fourth day after injury.

Proteolytic enzyme activity in patients with severe head injury and the effect of a proteinase inhibitor

A study was performed to detect the inhibitory effect of intravenously administered aprotinin (Trasylol) on brain and CSF protease activity in 25 patients with severe head injury. The data presented include measurements of CSF protease activity, alpha-1-antitrypsin, alpha-2-macroglobulin, haptoglobulin, polyacrylamidgel-electrophoresis pattern, total protein and hemoglobin content. The results indicate that increased protease activity is present and that this induces autolytic processes which can be inhibited by aprotinin treatment. The survival rate was higher after aprotinin treatment. Total CSF protein content was significantly higher in nonsurvivors than in survivors.