Beneficial Effect of Methylprednisolone on Cardiac Myocytes in a Rat Model of Severe Brain Injury

Targeting hydrogen sulfide and nitric oxide to repair cardiovascular injury after trauma

The systemic cardiovascular effects of major trauma, especially neurotrauma, contribute to death and permanent disability in trauma patients and treatments are needed to improve outcomes. In some trauma patients, dysfunction of the autonomic nervous system produces a state of adrenergic overstimulation, causing either a sustained elevation in catecholamines (sympathetic storm) or oscillating bursts of paroxysmal sympathetic hyperactivity. Trauma can also activate innate immune responses that release cytokines and damage-associated molecular patterns into the circulation. This combination of altered autonomic nervous system function and widespread systemic inflammation produces secondary cardiovascular injury, including hypertension, damage to cardiac tissue, vascular endothelial dysfunction, coagulopathy and multiorgan failure. The gasotransmitters nitric oxide (NO) and hydrogen sulfide (H2S) are small gaseous molecules with potent effects on vascular tone regulation. Exogenous NO (inhaled) has potential therapeutic benefit in cardio-cerebrovascular diseases, but limited data suggests potential efficacy in traumatic brain injury (TBI). H2S is a modulator of NO signaling and autonomic nervous system function that has also been used as a drug for cardio-cerebrovascular diseases. The inhaled gases NO and H2S are potential treatments to restore cardio-cerebrovascular function in the post-trauma period.

High-dose glucocorticoid aggravates TBI-associated corticosteroid insufficiency by inducing hypothalamic neuronal apoptosis

Emerging experimental and clinical data suggest that severe illness, such as traumatic brain injury (TBI), can induce critical illness-related corticosteroid insufficiency (CIRCI). However, underlying mechanisms of this TBI-associated CIRCI remain poorly understood. We hypothesized that dexamethasone (DXM), a synthetic glucocorticoid, which was widely used to treat TBI, induces hypothalamic neuronal apoptosis to aggravate CIRCI. To test this hypothesis, we have evaluated the dose effect of DXM (1 or 10mg/kg) on the development of acute CIRCI in rats with fluid percussion injury-induced TBI and on cultured rat hypothalamic neurons in vitro (DXM, 10(-5)-10(-8)mol/L). Corticosterone Increase Index was recorded as the marker for CIRCI. In addition, MTT and TUNEL assays were used to measure the viability and apoptosis of hypothalamic neurons in primary culture. Moreover, high-resolution hopping probe ion conductance microscopy (HPICM) was used to monitor the DXM-induced morphological changes in neurons. The incidence of acute CIRCI was significantly higher in the high-dose DXM group on post-injury day 7. Cellular viability was significantly decreased from 12h to 24h after the treatment with a high-dose of DXM. A significantly increase in TUNEL positive cells were detected in cultured cells treated with a high-dose of DXM after 18h. Neurites of hypothalamic neuron were dramatically thinner and the numbers of dendritic beadings increased in neurons treated with the high dose of DXM for 12h. In conclusion, high-dose DXM induced hypothalamic neurons to undergo apoptosis in vivo and in vitro, which may aggravate TBI-associated CIRCI.

The neuroprotective effects of lidocaine and methylprednisolone in a rat model of retinal ischemia-reperfusion injury

Retinal ischemia is a common cause of visual impairment for humans and animals. The neuroprotective effects of lidocaine (LDC) and methylprednisolone (MP) upon retinal ischemic injury were investigated in a rat model. Sprague-Dawley rats were divided into 3 groups, the IR control, LDC and MP. A very high intraocular pressure (HIOP) and retinal ischemia were induced. In LDC group, LDC bolus (1.5 mg/kg) was i.v. injected 30 min before ischemia and then a constant rate infusion (CRI) with 2 mg/kg/hr was given until 60 min after reperfusion. In MP group, MP bolus (30 mg/kg) was i.v. administered twice at 2 min before and immediately after ischemia, respectively. The HIOP damage to retina was evaluated by electroretinogram (ERG) and morphometrical histology. The functional analysis of the retina by ERG revealed a 35.2% reduction of a-wave in the IR group, 49.7% reduction in the LDC group but no significant change in the MP group compared to normal controls. An 81.0% reduction of b-wave was observed in the IR group, 80.7% reduction in the LDC group and 17.6% reduction in the MP group. In the morphometrical histology, the retinal inner plexiform layer/outer nuclear layer (IPL/ONL) ratio was reduced to 48.8% in the IR group, 80.1% in the LDC group and 96.2% in MP group. In conclusion, the MP showed significantly good neuroprotective effects on retinal IR injury, and the LDC showed moderate neuroprotective effects demonstrated in retinal structure but not in retinal function.

Plasma interleukin-8 as a potential predictor of mortality in adult patients with severe traumatic brain injury

Because of complex pathophysiology and severe consequences, traumatic brain injuries (TBI) are an important medical problem. Pathophysiology of TBI includes local and systemic stress response, in which interleukin-8 (IL-8) is considered as a key mediator of neuroinflammation. However, prognostic relevance of IL-8 measurement in adult patients with severe TBI is not certain. Therefore, IL-8 was determined in blood samples from central venous and jugular bulb catheter and in cerebrospinal fluid of twenty patients with isolated TBI at admission to Intensive Care Unit. None of the patients had history of stroke, dementia, autoimmune diseases, acute infection or medication with anti-inflammatory drugs. Ten patients died due to traumatic brain injury, while the other ten recovered well. While there was no significant difference of IL-8 levels in cerebrospinal fluid between survivors and nonsurvivors, central venous plasma level of IL-8 was significantly lower in survivors (71.00 +/- 14.17 pg/ml), than in nonsurvivors (111.26 +/- 16.9 pg/ml). Receiver Operating Characteristic (ROC) analysis revealed significant prognostic value for IL-8 in the blood as well as for the age of patients, Glasgow Coma Scale (GCS) and Acute Physiologic and Chronic Health Evaluation (APACHE II). These findings suggest that the central venous plasma values of IL-8 at admission might be an early predictive marker in patients with severe TBI, comparative to standard clinical prognostic markers such as APACHE II and GCS.

Expression of antiapoptotic survivin and aven genes in rat heart tissue after traumatic brain injury

We have recently shown that experimental traumatic brain injury (TBI) results in ultrastructural damage in heart tissue. The aim of this study was to determine the two antiapoptotic signals "survivin" and "aven" in rat heart tissue following TBI, and comparing the effects of erythropoietin (EPO) and methylprednisolone (MPS). Thirty-six Wistar-Albino female rats weighing 190 to 230 g were randomly allocated into six groups: group 1 underwent head trauma with no treatment; group 2 and group 3, head trauma and intraperitoneally delivered EPO (1000 IU/kg) and MPS (30 mg/kg), respectively; group 4 (vehicle), head trauma and intraperitoneal albumin (0.4 mL/rat); groups 5 and 6, control and sham-operated groups, respectively. Three-hundred g-cm impact trauma was produced by the method of weight-drop. Real-time quantitative polymerase chain reactions were used to estimate survivin and aven gene expression at the total RNA level. Both survivin and aven were higher among the treatment than the trauma group (P = .0006, .0001 and P = .0038, .0033, respectively). Comparing survivin and aven between EPO and MPS treatment groups showed no significance (P = .3027, .2171, respectively). Also, both survivin and aven were significantly higher among the treatment than the vehicle, the control, or the sham-operated groups. These findings suggested that both EPO and MPS may play important roles in the expression of antiapoptotic survivin and aven genes in heart tissue after TBI.

Neutrophils and the blood–brain barrier dysfunction after trauma

Despite the fact that neutrophils are essential for the protection from invading pathogens, hyperactive neutrophils may elicit detrimental cerebral damage after severe trauma. The neutrophil interactions with the neurovascular unit entail endothelial dysfunction involving endothelial leakage, formation of edema, coagulation abnormalities, disturbed hemodynamics, tissue infiltration etc. These elements of the "whole body inflammation," designated systemic inflammatory response syndrome (SIRS) in conjunction with intracerebral proinflammatory activities, are important triggers of post-traumatic cerebral damage and mortality according to the "second hit" concept. From the immunologic point of view, the brain is an immune privileged site, known to resist autodestructive inflammatory activity much more efficiently than other organs because of the highly efficient diverse functions of the blood-brain barrier (BBB). However, both the underlying strategy of the BBB to maintain cerebral protecting functions against the post-traumatic neutrophil-mediated "second hit" and how activated neutrophils may overcome the BBB are currently unknown. Therefore, this review summarizes the current understanding of the "second hit," the BBB physiology, and its role in the maintenance of cerebral immune privilege, and discusses recent findings that may explain the pathophysiologic neutrophil-BBB interactions occurring after severe trauma, thus offering novel therapeutic options to protect from post-traumatic brain damage.