Death to sepsis: targeting apoptosis pathways in sepsis

Environmental relevant concentrations of triclosan affected developmental toxicity, oxidative stress, and apoptosis in zebrafish embryos

Triclosan (TCS), as a broad-spectrum antibacterial agent, is widely used in various pharmaceutical and personal care products. However, the details of ecological environmental health risks of TCS are not clear. In this study, zebrafish embryos/larval were exposed to environmentally relevant concentrations of TCS to evaluate the developmental toxicity. Four-hour post-fertilization (hpf) zebrafish embryos were exposed to 0, 2, 10, 50, and 250 μg/L TCS until 96 h. The heart beats at 72 hpf were significantly increased in 2 μg/L TCS group, while significantly decreased in 250 μg/L TCS treated group compared with control. The results of acridine orange staining, terminal deoxynucleotide transferase-mediated UTPnick end labeling assay, and detection of mitochondrial membrane potential showed that 50 and 250 μg/L TCS resulted in apoptosis. Meanwhile, reactive oxygen species (ROS) and DNA damage were induced, but SOD activity was significantly decreased in 250 μg/L TCS treated group. In addition, SOD(Mn) and GPx gene mRNA expressions were significantly down-regulated in 50 and 250 μg/L TCS treated groups, while Casp3, Casp9, Puma, Casp8, Apaf1, and Bid genes in 250 μg/L TCS and Mdm2 gene in 50 μg/L treated groups were significantly up-regulated. P53 protein was significantly up-regulated in 250 μg/L TCS treated group. The overall results showed that TCS can cause oxidative stress and result in apoptosis via the involvement of ROS-p53-caspase-dependent apoptotic pathway in zebrafish embryos. The present findings suggest the potential mechanisms of TCS-induced developmental toxicity appears to be the generation of ROS and the consequent triggering of apoptosis genes.

Is lymphopenia different between SARS and COVID-19 patients?

Lymphopenia is commonly observed in SARS and COVID-19 patients although the lymphocyte count is not always below 0.8 × 109 /L in all the patients. It is suggested that lymphopenia serves as a useful predictor for prognosis in the patients. It is also hypothesized that lymphopenia is related to glucocorticoids and apoptosis. However, the ordering between lymphopenia and apoptosis appears different between SARS and COVID-19 patients, ie, lymphopenia is prior to apoptosis in SARS patients whereas apoptosis is prior to lymphopenia in COVID-19 patients. This paper attempts to figure out this contradiction through three players, lymphopenia, glucocorticoids, and apoptosis. Although the literature does not provide a solid explanation, the level of glucocorticoids could determine the ordering between lymphopenia and apoptosis because the administration of high doses of glucocorticoids could lead to lymphopenia whereas low doses of glucocorticoids could benefit patients. In the meantime, this paper raises several questions, which need to be answered in order to better understand the whole course of COVID-19.

Beta-Blocker Therapy Preserves Normal Splenic T-Lymphocyte Numbers Reduced in Proportion to Sepsis Severity in a Sepsis Model

Lymphocyte cell death contributes to sepsis-induced immunosuppression, leading to poor prognosis. This study examined whether sepsis severity and beta-blocker therapy could affect the degree of T-lymphocyte cell death in a mouse model of sepsis. In the first control study, 20 animals were allocated to 4 groups: control group with sham operation (group C, n = 5) and 3 groups with cecum ligation and puncture (CLP) performed at 3 different sites: proximal, middle, and distal cecum (groups CLP-P, CLP-M, and CLP-D, respectively; n = 5 in each group). Their spleens were resected under general anesthesia 24 hours after CLP, and the total number of normal splenic T lymphocytes per mouse and the percentage of apoptotic T lymphocytes were evaluated using flow cytometry. In the second experimental study, the effect of the beta-blocker esmolol was examined in CLP-P (group CLP-PE vs. CLP-P; n = 5 in each group). The total normal splenic T-lymphocyte numbers per mouse significantly decreased in proportion to CLP severity (group C, 18.6 × 10⁶ (15 × 10⁶–23.6 × 10⁶); CLP-D, 9.2 × 10⁶ (8.8 × 10⁶–9.8 × 10⁶); CLP-M, 6.7 × 10⁶ (6.3 × 10⁶–7.0 × 10⁶); and CLP-P, 5.3 × 10⁶ (5.1 × 10⁶–6.8 × 10⁶)). Beta-blocker therapy restored T-lymphocyte numbers (group CLP-PE vs. CLP-P; 6.94 ± 1.52 × 10⁶ vs. 4.18 ± 1.71 × 10⁶; p=0.027) without affecting apoptosis percentage. Beta-blocker therapy might improve sepsis-induced immunosuppression via normal splenic T-lymphocyte preservation.

The effect of curcumin on sepsis-induced acute lung injury in a rat model through the inhibition of the TGF-β1/SMAD3 pathway

Curcumin has the potential to treat inflammatory diseases. This study investigated its effect on sepsis-induced acute lung injury (ALI) in a rat model. 125 healthy rats were randomly divided into five groups, including normal group, sham-operated group, sepsis group, dimethyl sulfoxide group, and curcumin-treated group (25 rats in each subgroup). Sepsis-induced acute lung injury was affected by cecal ligation and puncture surgery. At 0, 6, 12, 24, and 48 h after treatment, the lungs were harvested for histological and protein expression examinations. 24h after the initial treatment, real-time PCR and Western blot analysis showed that the expression of TGF-β1 and SMAD3-dependent signaling pathway was significantly decreased in the curcumin-treated group than other control groups (P<0.05). Therefore, curcumin played a protective role in sepsis-induced ALI, possibly through the inhibition of the expression of TGF-β1/SMAD3 pathway which may provide a new strategy for the treatment of sepsis-induced ALI.

The effects of dexmedetomidine on secondary acute lung and kidney injuries in the rat model of intra-abdominal sepsis

In the present study, the effects of dexmedetomidine on secondary lung and kidney injuries were studied in the rat model of intra-abdominal sepsis by immunohistological and biochemical examinations. We measured serum creatinine, kidney tissue malondialdehide and plasma neutrophil gelatinase-associated lipocalin levels. In order to evaluate tissue injury we determined kidney tissue mononuclear cell infiltration score, alveolar macrophage count, histological kidney and lung injury scores and kidney and lung tissue immunoreactivity scores. We demonstrated that dexmedetomidine attenuates sepsis-induced lung and kidney injuries and apoptosis in the rat model of sepsis. There is still need for comparative studies in order to determine the effects of dexmedetomidine on organ functions in early human sepsis.

Bench-to-bedside review: Immunoglobulin therapy for sepsis - biological plausibility from a critical care perspective

Sepsis represents a dysregulated host response to infection, the extent of which determines the severity of organ dysfunction and subsequent outcome. All trialled immunomodulatory strategies to date have resulted in either outright failure or inconsistent degrees of success. Intravenous immunoglobulin (IVIg) therapy falls into the latter category with opinion still divided as to its utility. This article provides a narrative review of the biological rationale for using IVIg in sepsis. A literature search was conducted using the PubMed database (1966 to February 2011). The strategy included the following text terms and combinations of these: IVIg, intravenous immune globulin, intravenous immunoglobulin, immunoglobulin, immunoglobulin therapy, pentaglobin, sepsis, inflammation, immune modulation, apoptosis. Preclinical and extrapolated clinical data of IVIg therapy in sepsis suggests improved bacterial clearance, inhibitory effects upon upstream mediators of the host response (for example, the nuclear factor kappa B (NF-κB) transcription factor), scavenging of downstream inflammatory mediators (for example, cytokines), direct anti-inflammatory effects mediated via Fcγ receptors, and a potential ability to attenuate lymphocyte apoptosis and thus sepsis-related immunosuppression. Characterizing the trajectory of change in immunoglobulin levels during sepsis, understanding mechanisms contributing to these changes, and undertaking IVIg dose-finding studies should be performed prior to further large-scale interventional trials to enhance the likelihood of a successful outcome.

Postoperative immune suppression in visceral surgery: characterisation of an intestinal mouse model

BACKGROUND

Postoperatively acquired immune dysfunction is associated with a higher mortality rate in case of septic complications. As details of this severe clinical problem are still unknown, animal models are essential to characterise the mechanisms involved.

METHODS

Mice were laparotomised and the small intestine was pressed smoothly in antegrade direction. For extension of trauma, the intestine was manipulated three times consecutively. Following this, the ex vivo cytokine release of splenocytes was determined. The degree of surgical trauma was analysed by detection of HMGB1 and IL-6 in serum and by neutrophil staining in the muscularis mucosae.

RESULTS

We adapted the previously described animal model of intestinal manipulation to provide a model of surgically induced immune dysfunction. Following intestinal manipulation, the mice showed elevated serum levels of HMGB1 and IL-6 and increased infiltration of granulocytes into the muscularis mucosae. Ex vivo cytokine release by splenocytes was suppressed in the postoperative period. The degree of suppression correlated with the extent of surgical trauma.

CONCLUSIONS

In this study, we describe a surgically induced immune dysfunction animal model, in which a significant surgical trauma is followed by an immune dysfunction. This model may be ideal for the characterisation of the postoperative immune dysfunction syndrome.

Prevention of lymphocyte apoptosis in septic mice with cancer increases mortality

Lymphocyte apoptosis is thought to have a major role in the pathophysiology of sepsis. However, there is a disconnect between animal models of sepsis and patients with the disease, because the former use subjects that were healthy prior to the onset of infection while most patients have underlying comorbidities. The purpose of this study was to determine whether lymphocyte apoptosis prevention is effective in preventing mortality in septic mice with preexisting cancer. Mice with lymphocyte Bcl-2 overexpression (Bcl-2-Ig) and wild type (WT) mice were injected with a transplantable pancreatic adenocarcinoma cell line. Three weeks later, after development of palpable tumors, all animals received an intratracheal injection of Pseudomonas aeruginosa. Despite having decreased sepsis-induced T and B lymphocyte apoptosis, Bcl-2-Ig mice had markedly increased mortality compared with WT mice following P. aeruginosa pneumonia (85 versus 44% 7-d mortality; p = 0.004). The worsened survival in Bcl-2-Ig mice was associated with increases in Th1 cytokines TNF-α and IFN-γ in bronchoalveolar lavage fluid and decreased production of the Th2 cytokine IL-10 in stimulated splenocytes. There were no differences in tumor size or pulmonary pathology between Bcl-2-Ig and WT mice. To verify that the mortality difference was not specific to Bcl-2 overexpression, similar experiments were performed in Bim(-/-) mice. Septic Bim(-/-) mice with cancer also had increased mortality compared with septic WT mice with cancer. These data demonstrate that, despite overwhelming evidence that prevention of lymphocyte apoptosis is beneficial in septic hosts without comorbidities, the same strategy worsens survival in mice with cancer that are given pneumonia.