Resuscitation with hydroxyethyl starch solution prevents CD4+ T-lymphocyte apoptosis and modulates the balance of T helper type 1 and T helper type 2 responses in the rat with traumatic virgule/shill hemorrhagic shock

Targeting Inflammation After Hemorrhagic Shock as a Molecular and Experimental Journey to Improve Outcomes: A Review

Hemorrhagic shock continues to be a major contributor to trauma-related fatalities globally, posing a significant and intricate pathophysiological challenge. The condition is marked by injury and blood loss, which activate molecular cascades that can quickly become harmful. The inflammatory response exhibits a biphasic pattern, beginning with a hyper-inflammatory phase that transitions into immunosuppression, posing significant obstacles to effective therapeutic interventions. This review article explores the intricate molecular mechanisms driving inflammation in hemorrhagic shock, emphasizing cellular signaling pathways, endothelial dysfunction, and immune activation. We discuss the role of molecular biomarkers in tracking disease progression and stratifying risk, with a focus on markers of endothelial dysfunction and inflammatory mediators as potential prognostic tools. Additionally, we assess therapeutic strategies, spanning traditional approaches like hemostatic resuscitation to advanced immunomodulatory treatments. Despite promising advancements in molecular monitoring and targeted therapies, challenges persist in bridging experimental findings with clinical applications. Future efforts must prioritize understanding the dynamic progression of inflammatory pathways and refining the timing of interventions to improve outcomes in hemorrhagic shock management.

Engagement of Posthemorrhagic Shock Mesenteric Lymph on CD4+ T Lymphocytes In Vivo and In Vitro

BACKGROUND

Immune dysfunction is associated with posthemorrhagic shock mesenteric lymph (PHSML) return. To determine the proliferation and cytokine production capacity of CD4⁺ T lymphocytes, the effect of PHSML drainage on spleen CD4⁺ T lymphocytes in a mouse model of hemorrhagic shock was assessed.

METHODS

The normal spleen CD4⁺ T lymphocytes were in vitro incubated with either drained normal mesenteric lymph (NML), PHSML during hypotension (PHSML-H), or PHSML from 0 h to 3 h after resuscitation (PHSML-R) to verify direct proliferation effects of PHSML.

RESULTS

Hemorrhagic shock led to reduction of proliferation and mRNA expression of interleukin 2 (IL-2) and IL-2 receptor in CD4⁺ T lymphocytes and to decrease in IL-2 and interferon γ (IFN-γ) levels in supernatants. In contrast, the interleukin-4 levels were increased. These effects were reversed by PHSML drainage. Moreover, NML incubation promoted CD4⁺ T lymphocyte proliferation, whereas both PHSML-H and PHSML-R treatment had a biphasic effects on CD4⁺ T lymphocyte proliferation, exhibiting an enhanced effect at early stages and an inhibitory effect at later stages. Compared with NML, PHSML-H increased IL-2 expression at 12 h, but decreased expression of both IL-2 and IFN-γ at 24 h. By contrast, PHSML-R induced significant increases in IL-2 and IFN-γ levels at 24 h. Interleukin-4 expression in CD4⁺ T lymphocytes was reduced at 12 h, but augmented at 24 h after incubation with either PHSML-H or PHSML-R.

CONCLUSIONS

The results indicate that PHSML has a direct inhibitory effect on CD4⁺ T lymphocyte proliferation that induces an inflammatory response, which is associated with cellular immune dysfunction.

Immune recovery after fluid resuscitation in rats with severe hemorrhagic shock

OBJECTIVE

To investigate the effects of resuscitation with normal saline (NS), hypertonic saline (HTS), and hydroxyethyl starch (HES) on regulatory T cells (Tregs), helper T 1 (Th1)/Th2 and cytotoxic T 1 (Tc1)/Tc2 profiles in the treatment of hemorrhagic shock.

METHODS

Rats subjected to severe hemorrhagic shock were resuscitated for 30 min with NS (n=8), HTS (n=8), or HES (n=8); sham (n=8) and naive control (n=8) groups were used for comparison. Following fluid resuscitation, the whole shed blood was reinfused for 30 min, and the rats were observed with continuous hemodynamic monitoring for 120 min. CD4⁺CD25⁺Foxp3⁺ Treg proportions, Th1/Th2 and Tc1/Tc2 profiles in spleen were analyzed by three-color flow cytometry.

RESULTS

The proportion of CD4⁺CD25⁺Foxp3⁺ Tregs and ratios of Th1/Th2 and Tc1/Tc2 did not differ among control, sham, and HTS groups, but were significantly lower in NS and HES groups (both P<0.05 vs. sham); NS and HES levels were similar. The level of Tc1 was significantly increased in HTS (P<0.05 vs. sham), and levels of Tc2 were increased in NS, HES, and HTS groups compared to sham (all P<0.05), but did not differ from each other.

CONCLUSIONS

HTS resuscitation has a greater impact on immune system recovery than NS or HES by preserving the proportion of Tregs and maintaining the balance between Th1/Th2 and Tc1/Tc2 cells in the spleen. Thus, HTS resuscitation provides potential immunomodulatory activity in the early stage after hemorrhagic shock.

Necroptosis as a potential therapeutic target in multiple organ dysfunction syndrome

Purpose

To investigate how necroptosisis, i.e. programmed necrosis, is involved in MODS, and to examine whether Nec-1, a specific necroptosis inhibitor, ameliorates multiorgan injury in MODS.

Experimental Design

A model of MODS was established in six-week old SD rats using fracture trauma followed by hemorrhage. Control animals received sham surgery. Cell death form and necrosome formation were measured by fluorescence-activated cell sorting and western blotting. MODS rats were randomly assigned to receive Nec-1 or saline with pretreatment and once daily. The first end-point was 72 hours survival. Organ injury and dysfunction, inflammatory cytokine levels, and necroptotic execution protein expression were also recorded.

Results

Organ injury and dysfunction were significantly more severe in the MODS group than the sham group (all p<0.01). Furthermore, MODS-induced liver, lung and kidney tissue injury was characterized by necroptosis rather than apoptosis, and accompanied by necrosome formation. Compared to MODS group, Nec-1 administration significantly improved 72 hours survival (p<0.01). Nec-1 administration significantly reduced necroptosis-induced liver, lung and kidney injury and dysfunction, inhibited inflammatory cytokines production, inhibited release of necroptotic execution proteins such as high-mobility group box 1 and mixed-lineage kinase domain-like protein pseudokinase in MODS rats (all p<0.01).

Conclusions

These results suggest that necroptosis is involved the pathology of MODS. Further, a necroptotic inhibitor Nec-1 may be considered as an adjunct treatment for MODS.

Allicin ameliorates intraintestinal bacterial translocation after trauma/hemorrhagic shock in rats: The role of mesenteric lymph node dendritic cell

BACKGROUND

Intestinal dendritic cells play important roles in regulating the function of the intestinal immune barrier and the intestinal bacterial translocation. In this study, we aim to investigate the effects of allicin on the function of mesenteric lymph node-dendritic cells after trauma/hemorrhagic shock.

METHODS

One hundred and eight-four Sprague-Dawley rats were randomly assigned into a sham group (n = 46), sham + allicin group (n = 46), trauma/hemorrhagic shock group (n = 46), and trauma/hemorrhagic shock + allicin group (n = 46). Studies were performed on an in vivo model of spontaneously breathing rats with induced trauma/hemorrhagic shock. Allicin was diluted in resuscitation fluid and was administered through the right jugular vein. Flow cytometry was used to determine the expression of CD80, CD86, and major histocompatibility complex II (MHC II) on the surface of mesenteric lymph node-dendritic cells, as well as apoptosis. Intraintestinal bacterial translocation was monitored by using bioluminescent citrobacter. Intestinal permeability tests were conducted by using both FITC-Dextran and Ussing-Chember assay.

RESULT

CD80 and MHC-II expression levels were downregulated in the trauma/hemorrhagic shock group compared with the sham and sham + allicin groups; however, the expression was upregulated after allicin treatment. Also, allicin could ameliorate the trauma/hemorrhagic shock-induced increase in early apoptosis of mesenteric lymph node-dendritic cells. A significant increase was observed in the permeability of the intestinal barrier after severe traumatic shock, along with an obvious intraintestinal bacterial translocation to mesenteric lymph node. No difference was noticed in the bacterial translocation in mesenteric lymph node in the trauma/hemorrhagic shock group compared with trauma/hemorrhagic shock + allicin group (P = .589), which indicated allicin could not block bacterial translocation into mesenteric lymph node after trauma/hemorrhagic shock. However, it may increase the capacity of mesenteric lymph node to block intraintestinal bacterial translocation to extraintestinal organs as a statistical difference was noticed in the bacterial translocation in liver, blood, and spleen between trauma/hemorrhagic shock and trauma/hemorrhagic shock + allicin groups (P < .05).

CONCLUSION

Trauma/hemorrhagic shock resulted in a decrease of mature mesenteric lymph node-dendritic cells. Allicin treatment could block intraintestinal bacterial translocation through increasing the immunologic barrier function of mesenteric lymph node by modulating dendritic cells maturation.

Cutting edge: critical role for C5aRs in the development of septic lymphopenia in mice

In the early stages of sepsis, lymphocytes undergo apoptosis, resulting in lymphopenia and immunosuppression. The trigger for septic lymphopenia is unknown. Using the polymicrobial model of murine sepsis, we investigated the role of C5a receptors in septic lymphopenia. In wild-type mice, cecal ligation and puncture resulted in splenocyte apoptosis and significant lymphopenia after 3 d, which was not observed in C5aR1(-/-) or C5aR2(-/-) mice. Our data show that mouse neutrophils exposed to recombinant mouse C5a cause release of histones in a dose-dependent and time-dependent manner. Histone levels in spleen were significantly elevated following cecal ligation and puncture but were reduced by the absence of C5aR1. Histones induced significant lymphocyte apoptosis in vitro. Ab-mediated neutralization of histones prevented the development of lymphopenia in sepsis. Together, these results describe a new pathway of septic lymphopenia involving complement and extracellular histones. Targeting of this pathway may have therapeutic benefit for patients with sepsis or other serious illness.

Stress-induced neuroinflammation: role of the Toll-like receptor-4 pathway

BACKGROUND

Stressful challenges are associated with variations in immune parameters, including increased innate immunity/inflammation. Among possible mechanisms through which brain monitors peripheral immune responses, toll-like receptors (TLRs) recently emerged as the first line of defense against invading microorganisms. Their expression is modulated in response to pathogens and other environmental stresses.

METHODS

Taking into account this background, the present study aimed to elucidate whether the toll-like receptor-4 (TLR-4) signaling pathway is activated after repeated restraint/acoustic stress exposure in mice prefrontal cortex (PFC), the potential regulatory mechanism implicated (i.e., bacterial translocation), and its role in conditions of stress-induced neuroinflammation, using a genetic strategy: C3H/HeJ mice with a defective response to lipopolysaccharide stimulation of TLR-4.

RESULTS

Stress exposure upregulates TLR-4 pathway in mice PFC. Stress-induced inflammatory nuclear factor κB activation, upregulation of the proinflammatory enzymes nitric oxide synthase and cyclooxygenase type 2, and cellular oxidative/nitrosative damage are reduced when the TLR-4 pathway is defective. Conversely, TLR-4 deficient mice presented higher levels of the anti-inflammatory nuclear factor peroxisome proliferator activated receptor-gamma after stress exposure than control mice. The series of experiments using antibiotic intestinal decontamination also suggest a role for bacterial translocation on TLR-4 activation in PFC after stress exposure.

CONCLUSIONS

Taken together, all the data presented here suggest a bifunctional role of TLR-4 signaling pathway after stress exposure by triggering neuroinflammation at PFC level and regulating gut barrier function/permeability. Furthermore, our data suggest a possible protective role of antibiotic decontamination in stress-related pathologies presenting increased intestinal permeability (leaky gut) such as depression, showing a potential therapeutic target that deserves further consideration.

Establishment of an experimental mouse model of trauma-hemorrhagic shock

This study established an experimental mouse model of trauma-hemorrhagic shock (THS). THS-induced mice (C57BL/6J, n=33) were subjected to femoral fracture, ischemia for 90 min, and resuscitation for 15 min. The sham-operated mice (C57BL/6J, n=33) underwent the same anesthetic and surgical procedures, but neither trauma-hemorrhage nor fluid resuscitation were performed. Mean arterial pressure (MAP) and microvascular tissue perfusion over the small intestine, liver, and left kidney were longitudinally measured in all mice. Blood was collected for analysis at baseline and 3, 6, 12, and 24 h post resuscitation, and the small intestine, liver, and left kidney were resected for hematoxylin and eosin staining 24 h post resuscitation. Compared with the sham group, MAP and microvascular tissue perfusion over the small intestine, liver, and left kidney were all significantly reduced in the THS group at the end of hemorrhage. Following resuscitation, no significant differences were observed between the groups. THS induction was associated with significantly increased plasma concentrations of Cr, AST, CPK, IL-6, IL-10, and TNF-α from the baseline values by two- to three-fold after the hemorrhage phase, and THS-induced mice demonstrated significantly increased histological injury scores. The rapid drop in MAP and microvascular tissue perfusion observed following THS induction, and the gradual recovery post resuscitation, reflects the successful establishment of a THS experimental mouse model.

Trauma patients' elevated tumor necrosis related apoptosis inducing ligand (TRAIL) contributes to increased T cell apoptosis

Immunosuppression resulting from excessive post-trauma apoptosis of hyperactivated T cells is controversial. TRAIL mediated T cell apoptosis decreases highly activated T cells' responses. Caspase-10, a particular TRAIL target, was increased in trauma patients' T cells with concomitantly elevated plasma TRAIL levels. These patients' T cells developed anergy, implicating increased TRAIL-mediated T cell apoptosis in post-trauma T cell anergy. Control T cells cultured with patients' sera containing high TRAIL levels increased their caspase-10 activity and apoptosis. Stimulated primary T cells are TRAIL apoptosis resistant. Increased plasma thrombospondin-1 and T cell expression of CD47, a thrombospondin-1 receptor, preceded patients' T cell anergy. CD47 triggering of T cells increased their sensitivity to TRAIL-induced apoptosis. Augmentation of T cell TRAIL-induced apoptosis was secondary to CD47 triggered activation of the Src homology-containing phosphatase-1 (SHP-1) and was partially blocked by a SHP-1 inhibitor. We suggest that combined post-trauma CD47 triggering, SHP-1 mediated NFκB suppression, and elevated TRAIL levels increase patients' CD47 expressing T cell apoptosis, thus contributing to subsequent T cell anergy.

Inflammatory immune responses in a reproducible mouse brain death model

BACKGROUND

Brain death impairs donor organ quality and accelerates immune responses after transplantation. Detailed aspects of immune activation following brain death remain unclear. We have established a mouse model and investigated the immediate consequences of brain death and anesthesia on immune responses.

METHODS

C57JBl/6 mice (n=6/group) were anesthetized with isoflurane (ISF) or ketamine/xylazine (KX); subsequently, animals underwent brain death induction and were followed for 3h under continuous ventilation. Blood pressure was monitored continuously and animals were resuscitated with normal saline to achieve normotension. Immune activation in brain dead animals was analyzed by IFNγ-ELispot, MLR, and flow-cytometry. Sham-operated and naïve animals served as controls.

RESULTS

Blood pressure remained stable in both BD/KX and BD/ISF animals during the 3h observation time. Brain death was linked to systemic immune activation: IFNγ-expression of splenocytes and lymphocyte proliferation rates was significantly elevated subsequent to brain death (p<0.02, <0.01); T-cell activation markers CD28 and CD69 had increased in brain dead animals (p<0.03, <0.02). Isoflurane treatment in sham controls throughout the observation period (3.5h) revealed anesthesia associated IFNγ-expression and lymphocyte activation which were not observed when animals were treated with ketamine/xylazine (p<0.04, <0.009).

CONCLUSIONS

This study reports on a reproducible and hemodynamically stable brain death mouse model. Hemodynamic stability was not impacted through either isoflurane or ketamine/xylazine induction. Of clinical relevance, prolonged anesthesia with isoflurane had been linked to pro-inflammatory cytokine activation. Brain death caused systemic immune activation in organ donors.

Resuscitation with hydroxyethyl starch solution prevents bone marrow mononuclear apoptosis in a rat trauma-hemorrhagic shock model

BACKGROUND

: Trauma-hemorrhagic shock (T/HS) has been associated with multiorgan dysfunction, including bone marrow failure. This study examined apoptosis and morphologic alterations in bone marrow mononuclear cells (BMMNCs) with different volume therapies after T/HS.

METHODS

: T/HS was induced in groups of male Sprague-Dawley rats through a fracture of the left femur and continual bleeding for 30 minutes, followed by resuscitation with Ringer's lactate solution (RL), 6% hydroxyethyl starch solution (HES), or 5% albumin (ALB). Mean arterial blood pressure was monitored during the T/HS and resuscitation, and the impacts of various resuscitative fluids on apoptosis and morphology of BMMNCs at 24 hours and 48 hours after resuscitation were examined using flow cytometry, transferase-mediated dUTP nick-end labeling assay, and hematoxylin and eosin staining.

RESULTS

: Fluctuations in mean arterial blood pressure were homogenous among the three treatment groups. The percentage of early BMMNC apoptosis increased significantly at 24 hours and 48 hours (24.65% +/- 5.41% and 29.09% +/- 2.07%, respectively; p < 0.05), and the percentage of late BMMNC apoptosis increased to 13.43% +/- 2.82% (p < 0.05) at 48 hours in the T/HS + RL group. In contrast, resuscitation with HES alone dramatically attenuated the apoptosis. Resuscitation with ALB alleviated BMMNC apoptosis, except for late apoptosis at 48 hours. A greater number of apoptotic BMMNCs as well as morphologic alterations were shown using the transferase-mediated dUTP nick-end labeling assay and hematoxylin and eosin stain in the T/HS + RL group than in the HES or ALB groups.

CONCLUSION

: Intravascular volume replacement with HES showed prevention of BMMNC apoptosis at first 48 hours after T/HS compared with RL and ALB. These findings provide new insights into the intervention mechanism of HES on T/HS-related multiorgan dysfunction.

When apoptosis meets autophagy: deciding cell fate after trauma and sepsis

Apoptotic cell death is considered to be an underlying mechanism in immunosuppression and multiple organ dysfunction after trauma-hemorrhage and sepsis. Although studied intensively over the last decade, the role of other cell death mechanisms under similar pathophysiological conditions has remained elusive. Recently, autophagy has emerged as an important mediator of programmed cell death pathways. Here, we review recent advances in our understanding of apoptosis and autophagy and the crosstalk between these processes. We explore the coexistence of these two processes and the effects of autophagy on apoptosis after trauma-hemorrhage and sepsis. The inter-relationship between autophagy and apoptosis might unveil novel therapeutic approaches for the detection and treatment of trauma-hemorrhage and sepsis.