Hemorrhagic shock shifts the serum cytokine profile from pro- to anti-inflammatory after experimental traumatic brain injury in mice

Abstract

Secondary insults, such as hemorrhagic shock (HS), worsen outcome from traumatic brain injury (TBI). Both TBI and HS modulate levels of inflammatory mediators. We evaluated the addition of HS on the inflammatory response to TBI. Adult male C57BL6J mice were randomized into five groups (n=4 [naïve] or 8/group): naïve; sham; TBI (through mild-to-moderate controlled cortical impact [CCI] at 5 m/sec, 1-mm depth), HS; and CCI+HS. All non-naïve mice underwent identical monitoring and anesthesia. HS and CCI+HS underwent a 35-min period of pressure-controlled hemorrhage (target mean arterial pressure, 25-27 mm Hg) and a 90-min resuscitation with lactated Ringer's injection and autologous blood transfusion. Mice were sacrificed at 2 or 24 h after injury. Levels of 13 cytokines, six chemokines, and three growth factors were measured in serum and in five brain tissue regions. Serum levels of several proinflammatory mediators (eotaxin, interferon-inducible protein 10 [IP-10], keratinocyte chemoattractant [KC], monocyte chemoattractant protein 1 [MCP-1], macrophage inflammatory protein 1alpha [MIP-1α], interleukin [IL]-5, IL-6, tumor necrosis factor alpha, and granulocyte colony-stimulating factor [G-CSF]) were increased after CCI alone. Serum levels of fewer proinflammatory mediators (IL-5, IL-6, regulated upon activation, normal T-cell expressed, and secreted, and G-CSF) were increased after CCI+HS. Serum level of anti-inflammatory IL-10 was significantly increased after CCI+HS versus CCI alone. Brain tissue levels of eotaxin, IP-10, KC, MCP-1, MIP-1α, IL-6, and G-CSF were increased after both CCI and CCI+HS. There were no significant differences between levels after CCI alone and CCI+HS in any mediator. Addition of HS to experimental TBI led to a shift toward an anti-inflammatory serum profile--specifically, a marked increase in IL-10 levels. The brain cytokine and chemokine profile after TBI was minimally affected by the addition of HS.

Keywords: blast injury; chemokine; head injury; hypotension; interleukin; polytrauma; resuscitation.

FIG. 1.

Measured values of inflammatory mediators. Bars represent minimum to maximum values, and the dividing line represents the median. Brain tissue regions are ipsilateral hippocampus (blue), contralateral hippocampus (gray), ipsilateral parietal cortex (yellow), contralateral parietal cortex (white), and cerebellum (light blue). Color coding is also shown in the insert. Brain tissue values are plotted on the left axis in pg/mg of protein. Serum values (red) are plotted on the right axis in pg/mL of serum. Stars represent a significant difference versus control (sham for brain tissue and naïve for serum; p<0.05 for both). Double bars represent a significant difference versus controlled cortical impact (CCI) alone. (A) Eotaxin; (B) keratinocyte chemoattractant (KC); (C) interferon-inducible protein 10 (IP-10); (D) monocyte chemoattractant protein 1 (MCP-1); (E) macrophage inflammatory protein 1 alpha (MIP-1α); (F) interleukin (IL)-6; (G) granulocyte colony-stimulating factor (G-CSF); (H) IL-1α; (I) IL-5; (J) IL-10; (K) tumor necrosis factor alpha (TNF-α); and (L) regulated upon activation, normal T-cell expressed, and secreted (RANTES). HS, hemorrhagic shock. Color image is available online at www.liebertpub.com/neu

FIG. 1.

Measured values of inflammatory mediators. Bars represent minimum to maximum values, and the dividing line represents the median. Brain tissue regions are ipsilateral hippocampus (blue), contralateral hippocampus (gray), ipsilateral parietal cortex (yellow), contralateral parietal cortex (white), and cerebellum (light blue). Color coding is also shown in the insert. Brain tissue values are plotted on the left axis in pg/mg of protein. Serum values (red) are plotted on the right axis in pg/mL of serum. Stars represent a significant difference versus control (sham for brain tissue and naïve for serum; p<0.05 for both). Double bars represent a significant difference versus controlled cortical impact (CCI) alone. (A) Eotaxin; (B) keratinocyte chemoattractant (KC); (C) interferon-inducible protein 10 (IP-10); (D) monocyte chemoattractant protein 1 (MCP-1); (E) macrophage inflammatory protein 1 alpha (MIP-1α); (F) interleukin (IL)-6; (G) granulocyte colony-stimulating factor (G-CSF); (H) IL-1α; (I) IL-5; (J) IL-10; (K) tumor necrosis factor alpha (TNF-α); and (L) regulated upon activation, normal T-cell expressed, and secreted (RANTES). HS, hemorrhagic shock. Color image is available online at www.liebertpub.com/neu

FIG. 2.

Tumor necrosis factor alpha (TNF-α) levels assessed by enzyme-linked immunosorbent assay in cerebellum (CER), left and right parietal cortex (LPC and RPC, respectively), and left and right hippocampus (LH and RH, respectively) in naïve and non-naïve mice at 2 h after either controlled cortical impact (CCI) or CCI+HS (hemorrhagic shock). (A) Results from brain tissue samples homogenized with phosphate-buffered saline (PBS). (B) Results from samples homogenized with radioimmunoprecipitation assay (RIPA) buffer. *p<0.05 versus respective naïve.