Acute changes of pro-inflammatory markers and corticosterone in experimental subarachnoid haemorrhage: A prerequisite for severity assessment

Abstract

Many details of the pathophysiology of subarachnoid haemorrhage (SAH) still remain unknown, making animal experiments an indispensable tool for assessment of diagnostics and therapy. For animal protection and project authorization, one needs objective measures to evaluate the severity and burden in each model. Corticosterone is described as a sensitive stress parameter reflecting the acute burden, and inflammatory markers can be used for assessment of the extent of the brain lesion. However, the brain lesion itself may activate the hypothalamic-pituitary-adrenal-axis early after SAH, as shown for ischemic stroke, probably interfering with early inflammatory processes, thus complicating the assessment of severity and burden on the basis of corticosterone and inflammation. To assess the suitability of these markers in SAH, we evaluated the courses of corticosterone, IL-6 and TNF-α up to 6h in an acute model simulating SAH in continuously anaesthetized rats, lacking the pain and stress induced impact on these parameters. Animals were randomly allocated to sham or SAH. SAH was induced by cisterna magna blood-injection, and intracranial pressure and cerebral blood flow were measured under continuous isoflurane/fentanyl anaesthesia. Withdrawn at predetermined time points, blood was analysed by commercial ELISA kits. After 6h the brain was removed for western blot analysis of IL-6 and TNF-α. Serum corticosterone levels were low with no significant difference between sham and SAH. No activation of the HPA-axis was detectable, rendering corticosterone a potentially useful parameter for stress assessment in future chronic studies. Blood IL-6 and TNF-α increased in both groups over time, with IL-6 increasing significantly more in SAH compared to sham towards the end of the observation period. In the basal cortex, IL-6 and TNF-α increased only in SAH. The pro-inflammatory response seems to start locally in the brain, reflected by an increase in peripheral blood. An additional surgery-induced systemic inflammatory response should be considered.

Vascular Reactivity to Hypercapnia Is Impaired in the Cerebral and Retinal Vasculature in the Acute Phase After Experimental Subarachnoid Hemorrhage

“…A total of n = 15 animals were excluded for death during surgery ( n = 11), failed SAH induction ( n = 3), and uncontrollable bleeding from the surgery wound at the cranial window with distortion of CBF measurement ( n = 1; Figure 2 ). The ICP showed the typical course known from other studies of the group ( 10 , 24 ), presenting a high peak at the end of the 1 min blood-injection period, followed by a moderate, yet still significantly elevated plateau phase throughout the observation period (except for ICP in Iso—Group at 360 min), with no significant difference between both anesthesia protocols ( Supplementary Figure 1A ). With CBF starting from the baseline of 100%, after a transient severe drop to ischemic values at the time of the ICP peak (Iso—Group SAH: 6.1% [5.5–14.6], p < 0.0001; K/X—Group SAH: 9.3% [7.2–21.8], p < 0.0001; no significant difference between groups), CBF reached normal values again within 15 min in the K/X—Group and within 60 min in the Iso—Group, respectively.…”

“…For the cerebral circulation, it is known from this and our previous studies ( 10 , 24 ) that with isoflurane anesthesia strong hypoperfusion occurs up to 2 h after SAH induction in this model. We, therefore, compared the resting diameters of the retinal vessels (in arbitrary units), taken directly before the hypercapnic challenges, at baseline with each time point thereafter in Sham or SAH.…”

“…For the experiments, two different anesthesia protocols were used with the Iso—Group performed first, using our well-established regime ( 10 , 24 ), resulting in significant increases to hypercapnia in the retinal and the cerebral vasculature, albeit with some variability between the animals. It is well-known that isoflurane itself dilates systemic and cerebral vasculature, probably being partly responsible for the variability.…”

“…Surgical preparation and monitoring were conducted by the same surgeon and performed as previously described ( 10 , 24 ).…”

The evaluation of pituitary damage associated with cardiac arrest: An experimental rodent model

“…To the best of our knowledge, no studies have explored the effect of chest compression on pituitary function and its interactions with upstream/downstream hormonal systems. However, there are other acute injury models, such as subarachnoid hemorrhage 46 and stroke 47 , that used rats and showed an activation of the HPA axis. Therefore, it can be inferred that any alteration of the pituitary function may be identified as a result of the stress response, which includes CA, chest compression, and subsequent post-CA responses.…”