Sepsis chronically in MARS: systemic cytokine responses are always mixed regardless of the outcome, magnitude, or phase of sepsis.

The paradigm of systemic inflammatory response syndrome-to-compensatory anti-inflammatory response syndrome transition implies that hyperinflammation triggers acute sepsis mortality, whereas hypoinflammation (release of anti-inflammatory cytokines) in late sepsis induces chronic deaths. However, the exact humoral inflammatory mechanisms attributable to sepsis outcomes remain elusive. In the first part of this study, we characterized the systemic dynamics of the chronic inflammation in dying (DIE) and surviving (SUR) mice suffering from cecal ligation and puncture sepsis (days 6-28). In the second part, we combined the current chronic and previous acute/chronic sepsis data to compare the outcome-dependent inflammatory signatures between these two phases. A composite cytokine score (CCS) was calculated to compare global inflammatory responses. Mice were never sacrificed but were sampled daily (20 µl) for blood. In the first part of the study, parameters from chronic DIE mice were clustered into the 72, 48, and 24 h before death time points and compared with SUR of the same post-cecal ligation and puncture day. Cytokine increases were mixed and never preceded chronic deaths earlier than 48 h (3- to 180-fold increase). CCS demonstrated simultaneous and similar upregulation of proinflammatory and anti-inflammatory compartments at 24 h before chronic death (DIE 80- and 50-fold higher versus SUR). In the second part of the study, cytokine ratios across sepsis phases/outcomes indicated steady proinflammatory versus anti-inflammatory balance. CCS showed the inflammatory response in chronic DIE was 5-fold lower than acute DIE mice, but identical to acute SUR. The systemic mixed anti-inflammatory response syndrome-like pattern (concurrent release of proinflammatory and anti-inflammatory cytokines) occurs irrespective of the sepsis phase, response magnitude, and/or outcome. Although different in magnitude, neither acute nor chronic septic mortality is associated with a predominating proinflammatory and/or anti-inflammatory signature in the blood.

Mouse model of posttraumatic abdominal sepsis: survival advantage of females over males does not depend on the cecum size.

BACKGROUND: Regardless of whether alone or in combination, cecal ligation and puncture (CLP) is the most commonly used model to emulate human polymicrobial sepsis. Numerous CLP studies have shown that female mice survive better than males. In adult mice, this effect may be partly due to the unequal cecum mass (larger in males), as cecum ligation is frequently not size standardized. Comparing two ligation approaches, we investigated whether cecum size influences gender-specific outcome differences. METHODS: 15-month-old (middle-aged) female and male CD-1 mice underwent sublethal trauma/hemorrhage followed by CLP 48 h later. The evaluation of cecum size (in centimeters) and filling (score) was immediately followed by two ligation protocols: (1) ileocecal ligation (IC-L; n = 28/each gender) below the ileocecal valve, and (2) apex ligation (AP-L; n = 31 males, n = 24 females) 2 cm from the apex ceci - all followed by an identical double puncture and 10-day monitoring. RESULTS: Cecum length (3.4 cm in males vs. 2.65 cm in females) and filling (2.5 score points in males vs. 1.7 in females; both p < 0.05) were always greater in male than female mice (27 vs. 44%, respectively). Compared to AP-L, the 10-day CLP mortality was higher with IC-L (86% in males and 61% in females), and this exacerbation was similar in both genders (by 21% in male and 23% in female mice). Finally, the intergender comparison demonstrated that female mice displayed a significant and similar survival advantage regardless of the ligation approach: the difference reached 25% with IC-L and 24% with AP-L. CONCLUSIONS: Standardization by AP-L did not eliminate the gender-specific difference in mortality due to posttraumatic sepsis. The greater cecum length/filling in middle-aged male mice was not responsible for their inferior survival compared to females.

Experimentally approaching the ICU: monitoring outcome-based responses in the two-hit mouse model of posttraumatic sepsis.

To simulate and monitor the evolution of posttraumatic sepsis in mice, we combined a two-hit model of trauma/hemorrhage (TH) followed by polymicrobial sepsis with repetitive blood sampling. Anesthetized mice underwent femur fracture/sublethal hemorrhage and cecal ligation and puncture (CLP) 48 h later. To monitor outcome-dependent changes in circulating cells/biomarkers, mice were sampled daily (facial vein) for 7 days and retrospectively divided into either dead (DIE) or surviving (SUR) by post-CLP day 7. Prior to CLP, AST was 3-fold higher in DIE, while all other post-TH changes were similar between groups. There was a significant post-CLP intergroup separation. In SUR, RBC and Hb were lower, platelets and neutrophils higher, and lymphocytes mixed compared to DIE. In DIE, all organ function markers except glucose (decrease) were few folds higher compared to SUR. In summary, the combination of daily monitoring with an adequate two-hit model simulates the ICU setting, allows insight into outcome-based responses, and can identify biomarkers indicative of death in the acute posttraumatic sepsis in mice.

Why do they die? Comparison of selected aspects of organ injury and dysfunction in mice surviving and dying in acute abdominal sepsis.

BACKGROUND: The mechanisms of sepsis mortality remain undefined. While there is some evidence of organ damage, it is not clear whether this damage alone is sufficient to cause death. Therefore, we aimed to examine contribution of organ injury/dysfunction to early deaths in the mouse abdominal sepsis. METHODS: Female OF-1 mice underwent either medium-severity cecal ligation and puncture (CLP-Only) or non-lethal CLP-ODam (CLP with cisplatin/carbontetrachloride to induce survivable hepatotoxicity and nephrotoxicity). In the first experiment, blood was collected daily from survivors (SUR; CLP-Only and CLP-ODam groups) or until early death (DIED; CLP-Only). In the second experiment (CLP-Only), early outcome was prospectively predicted based on body temperature (BT) and pairs of mice predicted to survive (P-SUR) and die (P-DIE) were sacrificed post-CLP. The overall magnitude of organ injury/dysfunction was compared in retrospectively and prospectively stratified mice. RESULTS: At day 7 post-CLP, survival in CLP-Only was 48%, while CLP-ODam was non-lethal. In CLP-Only mice within 24 h of death, urea increased to 78 (versus 40 mg/dl in SUR), ALT to 166 (vs. 108 U/l), LDH to 739 (vs. 438 U/l) and glucose declined to 43 (vs. 62 mg/dl). In CLP-ODam, hypoglycemia was exacerbated (by 1.5-fold) and ALT and LDH were 20- and 8-fold higher versus DIED (CLP-Only) mice. In CLP-Only, predicted deaths (P-DIE) were preceded by a significant rise only in cystatin C (268 vs. 170 ng/ml in P-SUR) but not in creatinine and troponin I. Respiratory function of mitochondria in the liver and kidney of P-SUR and P-DIE CLP-Only mice was not impaired (vs. controls) and ATP level in organs remained similar among all groups. Histologic injury scores in the liver, kidney, heart and lung showed no major disparities among dying, surviving and control mice. CONCLUSIONS: In CLP-Only mice, although the deregulation of parameters indicative of organ injury/dysfunction was greater in dying versus surviving mice, it never exceeded the changes in surviving CLP-ODam animals, and it was not followed by histopathological damage and/or mitochondrial dysfunction. This shows that interpretation of the contribution of the organ injury/dysfunction to early deaths in the CLP model is not straightforward and depends on the pathophysiological origin of the profiled disturbances.

Estrus cycle status defined by vaginal cytology does not correspond to fluctuations of circulating estrogens in female mice.

Gender-oriented studies in shock, trauma, and/or sepsis require accurate monitoring of hormonal fluctuations as estrogens may influence various end points. Yet, monitoring is challenging in small laboratory animals: e.g., despite its subjectivity, vaginal smears are the major method for determination of estrus cycle phases in mice. Using female mice of different age, we aimed to (a) characterize general age-related changes in systemic estrogens and (b) examine the utility of determination of the estrus cycle by vaginal smears and/or impedance simultaneously comparing them with oscillation of systemic estrogens. In this study, 3-, 15-, and 20-month-old mice underwent vaginal smear and impedance examination each morning for 22 days. Ten hours after each morning checkup, feces were collected, and a second vaginal smear performed. Blood was collected on days 15 and 22. In 3-month-old females, estrus (by smears) was three times more frequent than in older mice, but mean concentrations of plasma and fecal estrogens never decreased with age. Collectively (not individually) plotted fecal estrogens values increased in the proestrus/estrus interphase (by smears) in 3-month-old mice only. Impedance typically peaked (4.5 Ω in 3-month-old mice) in the estrus phase, and only the prediction of estrus (highest area under the curve = 0.87 in 3-month-old) but not of other phases was possible. Regardless of age, individual cycle phase (by smears) never correlated with corresponding fecal estrogens, and estrus could not be predicted. In conclusion, while the fecal estrogens oscillation and frequency of estrus phase were affected by age, the systemic hormone release persisted. In mice, vaginal cytology did not reflect changes of systemic (fecal) estrogens, whereas impedance accurately identified estrus. The flaws and advantages of the examined monitoring methods should be considered in the design of future shock studies.

Repetitive low-volume blood sampling method as a feasible monitoring tool in a mouse model of sepsis.

Blood-based monitoring of immunoinflammatory and organ function fluctuations is essential in models of critical illness. This is challenging in diseased mice as repetitive blood collection may be harmful and/or affect end points. We studied the influence of daily sampling in acutely septic (days 1-5) mice upon survival and selected hematologic and organ function parameters. In addition, we tested the reliabilty of complete blood cell (CBC) count using resuspended blood cells. Female OF-1 and CD-1 mice underwent cecal ligation and puncture (CLP) and were subdivided into Daily and Day 5 groups. Blood was collected daily for 5 days in the Daily group and only on day 5 post-CLP in the Day 5 group. We tested 20 µL (both strains) and 35 µL (OF-1 mice) sampling volumes. The 35-µL volume simultaneously served to test the CBC reliabilty in resuspended versus unprocessed blood. Daily sampling did not affect the 14-day CLP mortality. Compared with the Day 5 group, daily 35-µL sampling in OF-1 mice decreased the red blood cell count and hemoglobin concentration by 22% and 23% (P < 0.05). In neither strain did daily 20-µL sampling affect the red blood cell count, whereas there was a 9% hemoglobin decrease (P < 0.05) in OF-1 mice. Although alanine aminotransferase, lactate dehydrogenase, and glucose levels were comparable, urea significantly increased by 24% in the Daily group (20-µL volume, OF-1 mice). Interleukin 6, platelets, and white blood cell counts remained unaffected. There was an excellent correlation between regular and resuspended CBC for all cell types (r ≥ 0.9; slope, ≥0.9), except lymphocytes (r > 0.5; slope, >0.5). This method provides a feasible and safe translation of clinically relevant daily immunomonitoring to the mouse sepsis model.