Management of pediatric renal trauma: Results from the American Association for Surgery and Trauma Multi-Institutional Pediatric Acute Renal Trauma Study

BACKGROUND

Pediatric renal trauma is rare and lacks sufficient population-specific data to generate evidence-based management guidelines. A nonoperative approach is preferred and has been shown to be safe. However, bleeding risk assessment and management of collecting system injury are not well understood. We introduce the Multi-institutional Pediatric Acute Renal Trauma Study (Mi-PARTS), a retrospective cohort study designed to address these questions. This article describes the demographics and contemporary management of pediatric renal trauma at Level I trauma centers in the United States.

METHODS

Retrospective data were collected at 13 participating Level I trauma centers on pediatric patients presenting with renal trauma between 2010 and 2019. Data were gathered on demographics, injury characteristics, management, and short-term outcomes. Descriptive statistics were used to report on demographics, acute management, and outcomes.

RESULTS

In total, 1,216 cases were included in this study. Of all patients, 67.2% were male, and 93.8% had a blunt injury mechanism. In addition, 29.3% had isolated renal injuries, and 65.6% were high-grade (American Association for the Surgery of Trauma Grades III-V) injuries. The mean Injury Severity Score was 20.5. Most patients were managed nonoperatively (86.4%), and 3.9% had an open surgical intervention, including 2.7% having nephrectomy. Angioembolization was performed in 0.9%. Collecting system intervention was performed in 7.9%. Overall mortality was 3.3% and was only observed in patients with multiple injuries. The rate of avoidable transfer was 28.2%.

CONCLUSION

The management and outcomes of pediatric renal trauma lack data to inform evidence-based guidelines. Nonoperative management of bleeding following renal injury is a well-established practice. Intervention for renal trauma is rare. Our findings reinforce differences from the adult population and highlights opportunities for further investigation. With data made available through Mi-PARTS, we aimed to answer pediatric specific questions, including a pediatric-specific bleeding risk nomogram, and better understanding indications for interventions for collecting system injuries.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level IV.

Time is domain: factors affecting primary fascial closure after trauma and non-trauma damage control laparotomy (data from the EAST SLEEP-TIME multicenter registry)

PURPOSE

Damage control laparotomy (DCL) is used for both traumatic and non-traumatic indications. Failure to achieve primary fascial closure (PFC) in a timely fashion has been associated with complications including sepsis, fistula, and mortality. We sought to identify factors associated with time to PFC in a multicenter retrospective cohort.

METHODS

We reviewed retrospective data from 15 centers in the EAST SLEEP-TIME registry, including age, comorbidities (Charlson Comorbidity Index [CCI]), small and large bowel resection, bowel discontinuity, vascular procedures, retained packs, number of re-laparotomies, net fluid balance after 24 h, trauma, and time to first takeback in 12-h increments to identify key factors associated with time to PFC.

RESULTS

In total, 368 patients (71.2% trauma, of which 50.6% were penetrating, median ISS 25 [16, 34], with median Apache II score 15 [11, 22] in non-trauma) were in the cohort. Of these, 92.9% of patients achieved PFC at 60.8 ± 72.0 h after 1.6 ± 1.2 re-laparotomies. Each additional re-laparotomy reduced the odds of PFC by 91.5% (95%CI 88.2-93.9%, p < 0.001). Time to first re-laparotomy was highly significant (p < 0.001) in terms of odds of achieving PFC, with no difference between 12 and 24 h to first re-laparotomy (ref), and decreases in odds of PFC of 78.4% (65.8-86.4%, p < 0.001) for first re-laparotomy after 24.1-36 h, 90.8% (84.7-94.4%, p < 0.001) for 36.1-48 h, and 98.1% (96.4-99.0%, p < 0.001) for > 48 h. Trauma patients had increased likelihood of PFC in two separate analyses (p = 0.022 and 0.002).

CONCLUSION

Time to re-laparotomy ≤ 24 h and minimizing number of re-laparotomies are highly predictive of rapid achievement of PFC in patients after trauma- and non-trauma DCL.

LEVEL OF EVIDENCE

2B.

Outcomes after ultramassive transfusion in the modern era: An Eastern Association for the Surgery of Trauma multicenter study

BACKGROUND

Despite the widespread institution of modern massive transfusion protocols with balanced blood product ratios, survival for patients with traumatic hemorrhage receiving ultramassive transfusion (UMT) (defined as ≥20 U of packed red blood cells [RBCs]) in 24 hours) remains low and resource consumption remains high. Therefore, we aimed to identify factors associated with mortality in trauma patients receiving UMT in the modern resuscitation era.

METHODS

An Eastern Association for the Surgery of Trauma multicenter retrospective study of 461 trauma patients from 17 trauma centers who received ≥20 U of RBCs in 24 hours was performed (2014-2019). Multivariable logistic regression and Classification and Regression Tree analysis were used to identify clinical characteristics associated with mortality.

RESULTS

The 461 patients were young (median age, 35 years), male (82%), severely injured (median Injury Severity Score, 33), in shock (median shock index, 1.2; base excess, -9), and transfused a median of 29 U of RBCs, 22 U of fresh frozen plasma (FFP), and 24 U of platelets (PLT). Mortality was 46% at 24 hours and 65% at discharge. Transfusion of RBC/FFP ≥1.5:1 or RBC/PLT ≥1.5:1 was significantly associated with mortality, most pronounced for the 18% of patients who received both RBC/PLT and RBC/FFP ≥1.5:1 (odds ratios, 3.11 and 2.81 for mortality at 24 hours and discharge; both p < 0.01). Classification and Regression Tree identified that age older than 50 years, low initial Glasgow Coma Scale, thrombocytopenia, and resuscitative thoracotomy were associated with low likelihood of survival (14-26%), while absence of these factors was associated with the highest survival (71%).

CONCLUSION

Despite modern massive transfusion protocols, one half of trauma patients receiving UMT are transfused with either RBC/FFP or RBC/PLT in unbalanced ratios ≥1.5:1, with increased associated mortality. Maintaining focus on balanced ratios during UMT is critical, and consideration of advanced age, poor initial mental status, thrombocytopenia, and resuscitative thoracotomy can aid in prognostication.

LEVEL OF EVIDENCE

Prognostic, level III.

Trauma and nontrauma damage-control laparotomy: The difference is delirium (data from the Eastern Association for the Surgery of Trauma SLEEP-TIME multicenter trial)

BACKGROUND

Damage-control laparotomy (DCL) has been used for traumatic and nontraumatic indications. We studied factors associated with delirium and outcome in this population.

METHODS

We reviewed DCL patients at 15 centers for 2 years, including demographics, Charlson Comorbidity Index (CCI), diagnosis, operations, and outcomes. We compared 30-day mortality; renal failure requiring dialysis; number of takebacks; hospital, ventilator, and intensive care unit (ICU) days; and delirium-free and coma-free proportion of the first 30 ICU days (DF/CF-ICU-30) between trauma (T) and nontrauma (NT) patients. We performed linear regression for DF/CF-ICU-30, including age, sex, CCI, achievement of primary fascial closure (PFC), small and large bowel resection, bowel discontinuity, abdominal vascular procedures, and trauma as covariates. We performed one-way analysis of variance for DF/CF-ICU-30 against traumatic brain injury severity as measured by Abbreviated Injury Scale for the head.

RESULTS

Among 554 DCL patients (25.8% NT), NT patients were older (58.9 ± 15.8 vs. 39.7 ± 17.0 years, p < 0.001), more female (45.5% vs. 22.1%, p < 0.001), and had higher CCI (4.7 ± 3.3 vs. 1.1 ± 2.2, p < 0.001). The number of takebacks (1.7 ± 2.6 vs. 1.5 ± 1.2), time to first takeback (32.0 hours), duration of bowel discontinuity (47.0 hours), and time to PFC were similar (63.2 hours, achieved in 73.5%). Nontrauma and T patients had similar ventilator, ICU, and hospital days and mortality (31.0% NT, 29.8% T). Nontrauma patients had higher rates of renal failure requiring dialysis (36.6% vs. 14.1%, p < 0.001) and postoperative abdominal sepsis (40.1% vs. 17.1%, p < 0.001). Trauma and NT patients had similar number of hours of sedative (89.9 vs. 65.5 hours, p = 0.064) and opioid infusions (106.9 vs. 96.7 hours, p = 0.514), but T had lower DF/CF-ICU-30 (51.1% vs. 73.7%, p = 0.029), indicating more delirium. Linear regression analysis indicated that T was associated with a 32.1% decrease (95% CI, 14.6%-49.5%; p < 0.001) in DF/CF-ICU-30, while achieving PFC was associated with a 25.1% increase (95% CI, 10.2%-40.1%; p = 0.001) in DF/CFICU-30. Increasing Abbreviated Injury Scale for the head was associated with decreased DF/CF-ICU-30 by analysis of variance (p < 0.001).

CONCLUSION

Nontrauma patients had higher incidence of postoperative abdominal sepsis and need for dialysis, while T was independently associated with increased delirium, perhaps because of traumatic brain injury.

LEVEL OF EVIDENCE

Therapeutic study, level IV.

Lumbar and sacral brucellosis due to queso fresco ingestion

Brucellosis is rare in the USA, with 100–200 cases reported annually. In this case we illustrate the complex management of spinal brucellosis. A 22-year-old male presented with 3 months of low back pain. Imaging revealed osteomyelitis/diskitis of L5/S1 and abscesses involving the pre-vertebral, epidural and pelvic recesses. Initial biopsies were inconclusive, but the patient later endorsed eating unpasteurized cheese (queso fresco) from Mexico; therefore, Brucella serology was sent and was positive. Despite aggressive antibiotic therapy there was disease progression. The patient underwent debridement of the involved vertebrae and drainage. Multiple cultures failed to grow the organisms, but Brucella polymerase chain reaction was positive. A month later he underwent a second vertebral debridement as well as placement of tobramycin impregnated beads in the vertebral space. He has since recovered. Surgery should be considered if there is a poor response to medical management and patients may need repeated debridement.

Safe phlebotomy reduction in stable pediatric liver and spleen injuries

PURPOSE

Pediatric blunt solid organ injury management based on hemodynamic monitoring rather than grade may safely reduce resource expenditure and improve outcomes. Previously we have reported a retrospectively validated management algorithm for pediatric liver and spleen injuries which monitors hemodynamics without use of routine phlebotomy. We hypothesize that stable blunt pediatric isolated splenic/liver injuries can be managed safely using a protocol reliant on vital signs and not repeat hemoglobin levels.

METHODS

A prospective multi-institutional study was performed at three pediatric trauma centers. All pediatric patients from 07/2016-12/2017 diagnosed with liver or splenic injuries were identified. If appropriate for the protocol, only a baseline hemoglobin was obtained unless hemodynamic instability as defined in an age-appropriate fashion was determined by treating physician discretion. Descriptive statistics were conducted.

RESULTS

One hundred four patients were identified of which 38 were excluded from the protocol. There was a significant difference in abnormal shock index, pediatric age-adjusted (SIPA) values, hematocrit, and percentage of patients with hemoglobin less than 10 between the excluded and included patients. Of the 66 patients managed on the protocol, four patients had to be removed, two each on day one and day two. Of those four patients, only one required intervention. There were no mortalities.

CONCLUSION

A phlebotomy limiting protocol may be a safe option for stable pediatric splenic and liver injuries cared for in a pediatric trauma center with the resources for rapid intervention should the need arise. The differences in groups highlight the importance of utilizing this protocol in the correct patient population. Reduced phlebotomy offers the potential for reduced resource expenditure without any evidence of increased morbidity or mortality.

LEVEL OF EVIDENCE

Level IV.

Sedation and paralytic use in open abdomen patients-results from the EAST SLEEP Survey

BACKGROUND

Patients with an open abdomen after trauma or emergency surgery may benefit from reduced sedation and chemical paralysis. We studied the effect of attending surgeon experience on sedation depth and paralytic use, as well as enteral nutrition and time between laparotomies.

METHODS

We performed an institutional review board-approved survey (Sedation Level after Emergent ExLap without Primary Fascial Closure) of the senior and active Eastern Association for the Surgery of Trauma membership using Qualtrics (Qualtrics, Inc, Provo, UT). We obtained 393/1,655 responses (23.7%). Spearman's rho was used for ordinal data, and multivariate logistic regression was used to adjust for trauma center level and presence of trainees in the relationship between surgeon experience and use of deep sedation.

RESULTS

Surgeon experience was associated with deep sedation (Richmond Agitation and Sedation Score ≤-3, P = .001) and chemical paralysis (P = .001). Surgeon experience was associated with less concern about delirium and more concern for evisceration as the reason for sedation depth (P = .001) and for paralysis (P = .001). Using multivariate logistic regression, surgeon experience was associated with deep sedation (odds ratio 3.6 [95% confidence interval 1.3, 10.4], P = .017 for ≥20 years; odds ratio 3.5 [95% confidence interval 1.1, 10.4], P = .025 for 15-20 years). Trauma center level was also significant (odds ratio 7.2 for Richmond Agitation and Sedation Score ≤-3 [95% confidence interval 1.7, 31.0], P = .008 for level III/IV versus level I/II). Increased surgeon experience was associated with delay of commencement of enteral feeds until return of bowel function (P = .013). Few respondents indicated willingness to extubate or mobilize open abdomen patients. Experienced surgeons were likely to wait for a defined time rather than for normalization of resuscitation markers to perform the first takeback laparotomy (P = .047) and waited longer between subsequent laparotomies (P = .004).

CONCLUSION

There were significant variations in practice among respondents based on the length of time since their last residency or fellowship, including variations that deviate from current best practice for management of patients with an open abdomen.

The associations between initial radiographic findings and interventions for renal hemorrhage after high-grade renal trauma: Results from the Multi-Institutional Genitourinary Trauma Study

BACKGROUND

Indications for intervention after high-grade renal trauma (HGRT) remain poorly defined. Certain radiographic findings can be used to guide the management of HGRT. We aimed to assess the associations between initial radiographic findings and interventions for hemorrhage after HGRT and to determine hematoma and laceration sizes predicting interventions.

METHODS

The Genitourinary Trauma Study is a multicenter study including HGRT patients from 14 Level I trauma centers from 2014 to 2017. Admission computed tomography scans were categorized based on multiple variables, including vascular contrast extravasation (VCE), hematoma rim distance (HRD), and size of the deepest laceration. Renal bleeding interventions included angioembolization, surgical packing, renorrhaphy, partial nephrectomy, and nephrectomy. Mixed-effect Poisson regression was used to assess the associations. Receiver operating characteristic analysis was used to define optimal cutoffs for HRD and laceration size.

RESULTS

In the 326 patients, injury mechanism was blunt in 81%. Forty-seven (14%) patients underwent 51 bleeding interventions, including 19 renal angioembolizations, 16 nephrectomies, and 16 other procedures. In univariable analysis, presence of VCE was associated with a 5.9-fold increase in risk of interventions, and each centimeter increase in HRD was associated with 30% increase in risk of bleeding interventions. An HRD of 3.5 cm or greater and renal laceration depth of 2.5 cm or greater were most predictive of interventions. In multivariable models, VCE and HRD were significantly associated with bleeding interventions.

CONCLUSION

Our findings support the importance of certain radiographic findings in prediction of bleeding interventions after HGRT. These factors can be used as adjuncts to renal injury grading to guide clinical decision making.

LEVEL OF EVIDENCE

Prognostic and Epidemiological Study, Level III and Therapeutic/Care Management, Level IV.

Screening for Harassment, Abuse, and Discrimination among Surgery Residents: An EAST Multicenter Trial

Estimating the prevalence of harassment, verbal abuse, and discrimination among residents is difficult as events are often under-reported. The purpose of this study was to determine the prevalence of discrimination and abuse among surgical residents using the HITS (Hurt, Insulted, Threatened with harm or Screamed at) screening tool. A multicenter, cross-sectional, survey-based study was conducted at five academic teaching hospitals. Of 310 residents, 76 (24.5%) completed the survey. The HITS screening tool was positive in 3.9 per cent. The most common forms of abuse included sexual harassment (28.9%), discrimination based on gender (15.7%), and discrimination based on ethnicity (7.9%). There was a positive correlation between individuals who reported gender discrimination and racial discrimination (r = 0.778, n = 13, P = 0.002). Individuals who experienced insults were more likely to experience physical threats (r = 0.437, n = 79, P < 0.001) or verbal abuse (r = 0.690, n = 79, P < 0.001). Discrimination and harassment among surgical residents in academic teaching hospitals across the United States is not uncommon. Further research is needed to determine the impact of these findings on resident attrition.

Screening for Harassment, Abuse, and Discrimination among Surgery Residents: An EAST Multicenter Trial

Estimating the prevalence of harassment, verbal abuse, and discrimination among residents is difficult as events are often under-reported. The purpose of this study was to determine the prevalence of discrimination and abuse among surgical residents using the HITS (Hurt, Insulted, Threatened with harm or Screamed at) screening tool. A multicenter, cross-sectional, survey-based study was conducted at five academic teaching hospitals. Of 310 residents, 76 (24.5%) completed the survey. The HITS screening tool was positive in 3.9 per cent. The most common forms of abuse included sexual harassment (28.9%), discrimination based on gender (15.7%), and discrimination based on ethnicity (7.9%). There was a positive correlation between individuals who reported gender discrimination and racial discrimination (r = 0.778, n = 13, P = 0.002). Individuals who experienced insults were more likely to experience physical threats (r = 0.437, n = 79, P < 0.001) or verbal abuse (r = 0.690, n = 79, P < 0.001). Discrimination and harassment among surgical residents in academic teaching hospitals across the United States is not uncommon. Further research is needed to determine the impact of these findings on resident attrition.

Tranexamic Acid in Civilian Trauma Care in the California Prehospital Antifibrinolytic Therapy Study

Introduction

Hemorrhage is one of the leading causes of death in trauma victims. Historically, paramedics have not had access to medications that specifically target the reversal of trauma-induced coagulopathies. The California Prehospital Antifibrinolytic Therapy (Cal-PAT) study seeks to evaluate the safety and efficacy of tranexamic acid (TXA) use in the civilian prehospital setting in cases of traumatic hemorrhagic shock.

Methods

The Cal-PAT study is a multi-centered, prospective, observational cohort study with a retrospective comparison. From March 2015 to July 2017, patients ≥ 18 years-old who sustained blunt or penetrating trauma with signs of hemorrhagic shock identified by first responders in the prehospital setting were considered for TXA treatment. A control group was formed of patients seen in the five years prior to data collection cessation (June 2012 to July 2017) at each receiving center who were not administered TXA. Control group patients were selected through propensity score matching based on gender, age, Injury Severity Scores, and mechanism of injury. The primary outcome assessed was mortality recorded at 24 hours, 48 hours, and 28 days. Additional variables assessed included total blood products transfused, the hospital and intensive care unit length of stay, systolic blood pressure taken prior to TXA administration, Glasgow Coma Score observed prior to TXA administration, and the incidence of known adverse events associated with TXA administration.

Results

We included 724 patients in the final analysis, with 362 patients in the TXA group and 362 in the control group. Reduced mortality was noted at 28 days in the TXA group in comparison to the control group (3.6% vs. 8.3% for TXA and control, respectively, odds ratio [OR]=0.41 with 95% confidence interval [CI] [0.21 to 0.8]). This mortality difference was greatest in severely injured patients with ISS >15 (6% vs 14.5% for TXA and control, respectively, OR=0.37 with 95% CI [0.17 to 0.8]). Furthermore, a significant reduction in total blood product transfused was observed after TXA administration in the total cohort as well as in severely injured patients. No significant increase in known adverse events following TXA administration were observed.

Conclusion

Findings from the Cal-PAT study suggest that TXA use in the civilian prehospital setting may safely improve survival outcomes in patients who have sustained traumatic injury with signs of hemorrhagic shock.

Perforated esophageal intervention focus (PERF) study: a multi-center examination of contemporary treatment

The treatment of esophageal perforation (EP) remains a significant clinical challenge. While a number of investigators have previously documented efficient approaches, these were mostly single-center experiences reported prior to the introduction of newer technologies: specifically endoluminal stents. This study was designed to document contemporary practice in the diagnosis and management of EP at multiple institutions around the world and includes early clinical outcomes. A five-year (2009-2013) multicenter retrospective review of management and outcomes for patients with thoracic or abdominal esophageal perforation was conducted. Demographics, etiology, diagnostic modalities, treatments, subsequent early outcomes as well as morbidity and mortality were captured and analyzed. During the study period, 199 patients from 10 centers in the United States, Canada, and Europe were identified. Mechanisms of perforation included Boerhaave syndrome (60, 30.1%), iatrogenic injury (65, 32.6%), and penetrating trauma (25, 12.6%). Perforation was isolated to the thoracic segment alone in 124 (62.3%), with 62 (31.2%) involving the thoracoabdominal esophagus. Mean perforation length was 2.5 cm. Observation was selected as initial management in 65 (32.7%), with only two failures. Direct operative intervention was initial management in 65 patients (32.6%), while 29 (14.6%) underwent esophageal stent coverage. Compared to operative intervention, esophageal stent patients were significantly more likely to be older (61.3 vs. 48.3 years old, P < 0.001) and have sustained iatrogenic mechanisms of esophageal perforation (48.3% vs.15.4%). Secondary intervention requirement for patients with perforation was 33.7% overall (66). Complications included sepsis (56, 28.1%), pneumonia (34, 17.1%) and multi-organ failure (23, 11.6%). Overall mortality was 15.1% (30). In contemporary practice, diagnostic and management approaches to esophageal perforation vary widely. Despite the introduction of endoluminal strategies, it continues to carry a high risk of mortality, morbidity, and need for secondary intervention. A concerted multi-institutional, prospectively collected database is ideal for further investigation.

Differential protein expression in exosomal samples taken from trauma patients

Traumatic brain injuries (TBI) are among the most misdiagnosed and underreported types of head trauma. The potential long-term impact of undiagnosed or incorrectly identified concussions and other head injuries are potentially devastating, as evidenced by the increasing societal burden exhibited by soldiers returning from combat and athletes in contact sports. Concussions and TBI are notoriously difficult to correctly diagnose and prognosis for these injuries is poorly understood. In order to increase the likelihood of successful diagnosis, treatment, and prediction of outcomes, a definitive differential diagnosis will need to be established. The establishment of a "trauma-specific profile" or a panel of known trauma markers will significantly aid in this goal. Small membrane vesicles called exosomes have been shown to contain proteins and injury-specific biomarkers. In the future it is possible that they could become an important tool, utilized for their diagnostic and therapeutic potential.

Chlorisondamine, a sympathetic ganglionic blocker, moderates the effects of whole-body irradiation (WBI) on early host defense to a live bacterial challenge

There is a growing consensus that long-term deficits in the brain are due to dynamic interactions between multiple neural and immune cell types. Specifically, radiation induces an inflammatory response, including changes in neuromodulatory pro- and anti-inflammatory cytokine secretion. The purpose of this study was to establish that there is sympathetic involvement in radiation-induced decrements early in in vivo immune function host defense. Female, 8-9 week-old C57BL/6J mice were exposed to whole-body irradiation (WBI). There were 8 groups with radiation (0 vs. 3 Gy protons), immune challenge (Escherichia coli) and exposure to the sympathetic ganglionic blocker, chlorisondamine (1 mg/kg weight, i.p.), as independent variables. Ten days post-irradiation, mice were inoculated with E. coli intraperitoneally and sacrificed 90-120 min later. The data suggest that radiation-induced changes in immune function may in part be mediated by the sympathetic nervous system. Briefly, we found that radiation augments the bacteria-induced inflammatory cytokine response, particularly those cytokines involved in innate immunity. However, this augmentation can be reduced by the ganglionic blockade.

Biological Effects of Passive Versus Active Scanning Proton Beams on Human Lung Epithelial Cells

The goal was to characterize differences in cell response after exposure to active beam scanning (ABS) protons compared to a passive delivery system. Human lung epithelial (HLE) cells were evaluated at various locations along the proton depth dose profile. The dose delivered at the Bragg peak position was essentially identical (∼4 Gy) with the two techniques, but depth dose data showed that ABS resulted in lower doses at entry and more rapid drop-off after the peak. Average dose rates for the passive and ABS beams were 1.1 Gy/min and 5.1 Gy/min, respectively; instantaneous dose rates were 19.2 Gy/min and 2,300 Gy/min (to a 0.5 × 0.5 mm2 voxel). Analysis of DNA synthesis was based on 3H-TdR incorporation. Quantitative real-time polymerase chain reaction (RT-PCR) was done to determine expression of genes related to p53 signaling and DNA damage; a total of 152 genes were assessed. Spectral karyotyping and analyses of the Golgi apparatus and cytokines produced by the HLE cells were also performed. At or near the Bragg peak position, ABS protons resulted in a greater decrease in DNA synthesis compared to passively delivered protons. Genes with >2-fold change (P < 0.05 vs. 0 Gy) after passive proton irradiation at one or more locations within the Bragg curve were BTG2, CDKN1A, IFNB1 and SIAH1. In contrast, many more genes had >2-fold difference with ABS protons: BRCA1, BRCA2, CDC25A, CDC25C, CCNB2, CDK1, DMC1, DNMT1, E2F1, EXO1, FEN1, GADD45A, GTSE1, IL-6, JUN, KRAS, MDM4, PRC1, PTTG1, RAD51, RPA1, TNF, WT1, XRCC2, XRCC3 and XRCC6BP1. Spectral karyotyping revealed numerous differences in chromosomal abnormalities between the two delivery systems, especially at or near the Bragg peak. Percentage of cells staining for the Golgi apparatus was low after exposure to passive and active proton beams. Studies such as this are needed to ensure patient safety and make modifications in ABS delivery, if necessary.

Analysis of a metalloporphyrin antioxidant mimetic (MnTE-2-PyP) as a radiomitigator: prostate tumor and immune status

Due to radiation-induced immune depression and development of pathologies such as cancer, there is increasing urgency to identify radiomitigators that are effective when administered after radiation exposure. The main goal of this study was to determine the radiomitigation capacity of MnTE-2-PyP[Mn(III) tetrakis (N-ethylpyridinium-2-yl) porphyrin], a superoxide dismutase (SOD) mimetic, and evaluate leukocyte parameters in spleen and blood. C57BL/6 mice were total-body exposed to 2 Gy γ-rays (Co-60), i.e., well below a lethal dose, followed by subcutaneous implantation of 5 × 10(5) RM-9 prostate tumor cells and initiation of MnTE-2-PyP treatment (day 0); interval between each procedure was 1-2 h. The drug was administered daily (12 times). Tumor progression was monitored and immunological analyses were performed on a subset per group on day 12. Animals treated with MnTE-2-PyP alone had significantly slower tumor growth compared to mice that did not receive the drug (P < 0.05), while radiation alone had no effect. Treatment of tumor-bearing mice with MnTE-2-PyP alone significantly increased spleen mass relative to body mass; the numbers of splenic white blood cells (WBC) and lymphocytes (B and T), as well as circulating WBC, granulocytes, and platelets, were high compared to one of more of the other groups (P < 0.05). The results show that MnTE-2-PyP slowed RM-9 tumor progression and up-regulated immune parameters, but mitigation of the effects of 2 Gy total-body irradiation were minimal.

Comparison of proton and electron radiation effects on biological responses in liver, spleen and blood

PURPOSE

To determine whether differences exist between proton and electron radiations on biological responses after total-body exposure.

MATERIALS AND METHODS

ICR mice (n=45) were irradiated to 2 Gray (Gy) using fully modulated 70 MeV protons (0.5 Gy/min) and 21 MeV electrons (3 Gy/min). At 36 h post-irradiation liver gene expression, white blood cell (WBC), natural killer (NK) cell and other analyses were performed.

RESULTS

Oxidative stress-related gene expression patterns were strikingly different for irradiated groups compared to 0 Gy (P<0.05). Proton radiation up-regulated 15 genes (Ctsb, Dnm2, Gpx5, Il19, Il22, Kif9, Lpo, Nox4, Park7, Prdx4, Prdx6, Rag2, Sod3, Srxn1, Xpa) and down-regulated 2 genes (Apoe, Prdx1). After electron irradiation, 20 genes were up-regulated (Aass, Ctsb, Dnm2, Gpx1, Gpx4, Gpx5, Gpx6, Gstk1, Il22, Kif9, Lpo, Nox4, Park7, Prdx3, Prdx4, Prdx5, Rag2, Sod1, Txnrd3, Xpa) and 1 was down-regulated (Mpp4). Of the modified genes, only 11 were common to both forms of radiation. Comparison between the two irradiated groups showed that electrons significantly up-regulated three genes (Gstk1, Prdx3, Scd1). Numbers of WBC and major leukocyte types were low in the irradiated groups (P<0.001 vs. 0 Gy). Hemoglobin and platelet counts were low in the electron-irradiated group (P<0.05 vs. 0 Gy). However, spleens from electron-irradiated mice had higher WBC and lymphocyte counts, as well as enhanced NK cell cytotoxicity, compared to animals exposed to protons (P<0.05). There were no differences between the two irradiated groups in body mass, organ masses, and other assessed parameters, although some differences were noted compared to 0 Gy.

CONCLUSION

Collectively, the data demonstrate that at least some biological effects induced by electrons may not be directly extrapolated to protons.

Low-dose Photon and Simulated Solar Particle Event Proton Effects on Foxp3+ T Regulatory Cells and other Leukocytes

Radiation is a major factor in the spaceflight environment that has carcinogenic potential. Astronauts on missions are continuously exposed to low-dose/low-dose-rate (LDR) radiation and may receive relatively high doses during a solar particle event (SPE) that consists primarily of protons. However, there are very few reports in which LDR photons were combined with protons. In this study, C57BL/6 mice were exposed to 1.7 Gy simulated SPE (sSPE) protons over 36 h, both with and without pre-exposure to 0.01 Gray (Gy) LDR γ-rays at 0.018 cGy/h. Apoptosis in skin samples was determined by immunohistochemistry immediately post-irradiation (day 0). Spleen mass relative to body mass, white blood cells (WBC), major leukocyte populations, lymphocyte subsets (T, Th, Tc, B, NK), and CD4+ CD25+ Foxp3+ T regulatory (Treg) cells were analyzed on days 4 and 21. Apoptosis in skin samples was evident in all irradiated groups; the LDR+sSPE mice had the greatest expression of activated caspase-3. On day 4 post-irradiation, the sSPE and LDR+sSPE groups had significantly lower WBC counts in blood and spleen compared to non-irradiated controls ( p < 0.05 vs. 0 Gy). CD4+ CD25+ Foxp3+ Treg cell numbers in spleen were decreased at day 4, but proportions were increased in the sSPE and LDR+sSPE groups ( p < 0.05 vs. 0 Gy). By day 21, lymphocyte counts were still low in blood from the LDR+sSPE mice, especially due to reductions in B, NK, and CD8+ T cytotoxic cells. The data demonstrate, for the first time, that pre-exposure to LDR photons did not protect against the adverse effects of radiation mimicking a large solar storm. The increased proportion of immunosuppressive CD4+ CD25+ Foxp3+ Treg and persistent reduction in circulating lymphocytes may adversely impact immune defenses that include removal of sub-lethally damaged cells with carcinogenic potential, at least for a period of time post-irradiation.

Low-dose, low-dose-rate proton radiation modulates CD4(+) T cell gene expression

PURPOSE

To evaluate cluster of differentiation 4(+) (CD4(+)) T cell gene expression and related parameters after whole-body exposure to proton radiation as it occurs in the spaceflight environment.

MATERIALS AND METHODS

C57BL/6 mice were irradiated to total doses of 0, 0.01, 0.05, and 0.1 gray (Gy) at 0.1 cGy/h. On day 0 spleens were harvested from a subset in the 0, 0.01 and 0.1 Gy groups; (CD4(+)) T cells were isolated; and expression of 84 genes relevant to T helper (Th) cell function was determined using reverse transcriptase-polymerase chain reaction (RT-PCR). Remaining mice were euthanized on days 0, 4, and 21 for additional analyses.

RESULTS

Genes with >2-fold difference and p < 0.05 compared to 0 Gy were noted. After 0.01 Gy, five genes were up-regulated (Ccr5, Cd40, Cebpb, Igsf6, Tnfsf4) and three were down-regulated (Il4ra, Mapk8, Nfkb1). After 0.1 Gy there were nine up-regulated genes (Ccr4, Cd40, Cebpb, Cxcr3, Socs5, Stat4, Tbx21, Tnfrsf4, Tnfsf4); none were down-regulated. On day 0 after 0.01 Gy, CD4(+) T cell counts and CD4:CD8 ratio were low in the spleen (p < 0.05). Spontaneous DNA synthesis in both spleen and blood was lowest in the 0.01 Gy group on day 0; on days 4 and 21 all p values were >0.1.

CONCLUSION

The data show that the pattern of gene expression in CD4(+) T cells after protracted low-dose proton irradiation was significantly modified and highly dependent upon total dose. The findings also suggest that low-dose radiation, especially 0.01 Gy, may enhance CD4(+) T cell responsiveness.

Effects of spaceflight on innate immune function and antioxidant gene expression

Spaceflight conditions have a significant impact on a number of physiological functions due to psychological stress, radiation, and reduced gravity. To explore the effect of the flight environment on immunity, C57BL/6NTac mice were flown on a 13-day space shuttle mission (STS-118). In response to flight, animals had a reduction in liver, spleen, and thymus masses compared with ground (GRD) controls (P < 0.005). Splenic lymphocyte, monocyte/macrophage, and granulocyte counts were significantly reduced in the flight (FLT) mice (P < 0.05). Although spontaneous blastogenesis of splenocytes in FLT mice was increased, response to lipopolysaccharide (LPS), a B-cell mitogen derived from Escherichia coli, was decreased compared with GRD mice (P < 0.05). Secretion of IL-6 and IL-10, but not TNF-alpha, by LPS-stimulated splenocytes was increased in FLT mice (P < 0.05). Finally, many of the genes responsible for scavenging reactive oxygen species were upregulated after flight. These data indicate that exposure to the spaceflight environment can increase anti-inflammatory mechanisms and change the ex vivo response to LPS, a bacterial product associated with septic shock and a prominent Th1 response.

Low dose, low dose rate photon radiation modifies leukocyte distribution and gene expression in CD4(+) T cells

A better understanding of low dose radiation effects is needed to accurately estimate health risks. In this study, C57BL/6 mice were gamma-irradiated to total doses of 0, 0.01, 0.05, and 0.1 Gy ((57)Co; ~0.02 cGy/h). Subsets per group were euthanized at the end of irradiation (day 0) and on days 4 and 21 thereafter. Relative spleen mass and splenic white blood cell (WBC) counts, major leukocyte populations, and spontaneous DNA synthesis were consistently higher in the irradiated groups on day 0 compared to 0 Gy controls, although significance was not always obtained. In the spleen, all three major leukocyte types were significantly elevated on day 0 (P < 0.05). By day 21 post-irradiation the T, B, and natural killer (NK) cell counts, as well as CD4(+) T cells and CD4:CD8 T cell ratio, were low especially in the 0.01 Gy group. Although blood analyses showed no significant differences in leukocyte counts or red blood cell and platelet characteristics, the total T cells, CD4(+) T cells, and NK cells were increased by day 21 after 0.01 Gy (P < 0.05). Gene analysis of CD4(+) T cells negatively isolated from spleens on day 0 after 0.1 Gy showed significantly enhanced expression of Il27 and Tcfcp2, whereas Inha and Socs5 were down-regulated by 0.01 Gy and 0.1 Gy, respectively (P < 0.05). A trend for enhancement was noted in two additional genes (Il1r1 and Tbx21) in the 0.1 Gy group (P < 0.1). The data show that protracted low dose photons had dose- and time-dependent effects on CD4(+) T cells after whole-body exposure.

Effect of a metalloporphyrin antioxidant (MnTE-2-PyP) on the response of a mouse prostate cancer model to radiation

BACKGROUND

Metalloporphyrin antioxidants can protect tissues against radiation-induced damage. However, for effective use in radiotherapy as normal tissue radioprotectants, they must not protect the cancer. The major objectives were to evaluate the effects of Mn (III) tetrakis (N-ethylpyridinium-2-yl) porphyrin (MnTE-2-PyP) on tumor response to radiation and to explore mechanisms responsible for the observed effects.

MATERIALS AND METHODS

C57BL/6 mice were subcutaneously (s.c.) injected with RM-9 prostate tumor cells on day 0 and grouped according to treatment with MnTE-2-PyP (s.c. 6 mg/kg/day beginning on day 1 for 16 maximum days), 10 Gray (Gy) single fraction radiation on day 7, a combination of both or neither. Subsets per group and non-tumor bearing controls were evaluated for leukocyte populations, red blood cell (RBC) and platelet characteristics and cytokines on day 12; the remaining mice were followed for tumor growth.

RESULTS

Although radiation alone significantly slowed tumor growth and the addition of MnTE-2-PyP resulted in slightly slower tumor progression, the difference between radiation and radiation plus drug was not statistically significant. However, the treatment with drug alone significantly elevated T (helper, Th and cyotoxic, Tc) and natural killer (NK) cells in the spleen, B-cells in the blood and spleen, and the capacity to produce interleukin-2. The addition of the drug to radiation did not ameliorate the depression seen in all the major leukocyte types, but did protect against radiation-induced decreases in RBC counts, hemoglobin and hematocrit. Vascular endothelial growth factor (VEGF) increased in the plasma from both the irradiated groups and a trend for increased transforming growth factor-beta1 (TGF-beta1) was noted with radiation alone.

CONCLUSION

MnTE-2-PyP did not protect RM-9 prostate tumors against radiation damage and was not toxic under the conditions used. The drug-induced enhancement of certain immune parameters suggests that MnTE-2-PyP may be beneficial not only as a normal tissue radioprotectant, but also as a facilitator of antitumor immunity.

Spaceflight effects on T lymphocyte distribution, function and gene expression

The immune system is highly sensitive to stressors present during spaceflight. The major emphasis of this study was on the T lymphocytes in C57BL/6NTac mice after return from a 13-day space shuttle mission (STS-118). Spleens and thymuses from flight animals (FLT) and ground controls similarly housed in animal enclosure modules (AEM) were evaluated within 3-6 h after landing. Phytohemagglutinin-induced splenocyte DNA synthesis was significantly reduced in FLT mice when based on both counts per minute and stimulation indexes (P < 0.05). Flow cytometry showed that CD3(+) T and CD19(+) B cell counts were low in spleens from the FLT group, whereas the number of NK1.1(+) natural killer (NK) cells was increased (P < 0.01 for all three populations vs. AEM). The numerical changes resulted in a low percentage of T cells and high percentage of NK cells in FLT animals (P < 0.05). After activation of spleen cells with anti-CD3 monoclonal antibody, interleukin-2 (IL-2) was decreased, but IL-10, interferon-gamma, and macrophage inflammatory protein-1alpha were increased in FLT mice (P < 0.05). Analysis of cancer-related genes in the thymus showed that the expression of 30 of 84 genes was significantly affected by flight (P < 0.05). Genes that differed from AEM controls by at least 1.5-fold were Birc5, Figf, Grb2, and Tert (upregulated) and Fos, Ifnb1, Itgb3, Mmp9, Myc, Pdgfb, S100a4, Thbs, and Tnf (downregulated). Collectively, the data show that T cell distribution, function, and gene expression are significantly modified shortly after return from the spaceflight environment.

Variable hematopoietic responses to acute photons, protons and simulated solar particle event protons

The goal of this study was to evaluate, for the first time, the response of bone marrow-derived cell populations to protons mimicking a space radiation environment.

MATERIALS AND METHODS

C57BL/6 mice were exposed to 2 Gray (Gy) simulated solar particle event protons (sSPE) over 36 h; energies ranged from 15 to 215 MeV/n and were administered in 10 MeV increments. Acute 2 Gy irradiation with photons (gamma-rays) and protons were administered to different groups at 0.7 Gy/min and 0.9 Gy/min, respectively, for comparison with sSPE. The animals were euthanized on days 4 and 21 post-exposure for analyses.

RESULTS

Exposure to radiation, regardless of regimen, resulted in immune depression and other abnormalities in cell populations residing in the blood and spleen; the extent of the radiation damage was somewhat dependent upon body compartment and time postexposure. However, variations were also noted among the three radiation regimens in a number of measurements: relative spleen mass, basal DNA synthesis by leukocytes, white blood cell counts and three-part differentials (lymphocytes, granulocytes, monocytes-macrophages), lymphocyte subpopulations (CD4+ T, CD8+ T, B and NK cells) and erythrocyte and thrombocyte characteristics.

CONCLUSION

The data demonstrate that exposure to proton radiation mimicking a solar explosion induces abnormalities in leukocytes, erythrocytes and platelets that may have adverse health consequences. However, the damaging effects of sSPE on leukocytes and platelets were generally less pronounced compared to the other radiation regimens. Results obtained with photons (gamma-rays, X-rays) and monoenergetic protons at space-relevant total doses may not necessarily predict biological responses after exposure to a solar particle event.