Metabolic activation of WHO-congeners PCB28, 52, and 101 by human CYP2A6: evidence from in vitro and in vivo experiments.

Despite extensive research on the metabolism of polychlorinated biphenyls (PCBs), knowledge gaps persist regarding their isoform-specific biotransformation pathways. This study aimed to elucidate the role of different cytochrome P450 enzymes in PCB metabolism, focusing on WHO-congeners 2,4,4'-trichlorobiphenyl (PCB28), 2,2',5,5'-tetrachlorobiphenyl (PCB52), and 2,2',4,5,5'-pentachlorobiphenyl (PCB101). Utilizing engineered HEK293 cell lines, we investigated the in vitro metabolism of these PCBs by CYP1A2, CYP2C8, CYP2C9, CYP3A4, CYP2A6, and CYP2E1, revealing robust production of hydroxylated metabolites. Our results show that CYP2A6 plays a major role in the metabolism of these congeners responsible for predominant formation of para-position hydroxylated metabolites, with concentrations reaching up to 1.61 µg/L (5,89 nM) for PCB28, 316.98 µg/L (1,03 µM) for PCB52, and 151.1 µg/L (441 nM) for PCB101 from a 20 µM parent PCB concentration. Moreover, concentration-dependent cytotoxic and cytostatic effects induced by reactive intermediates of the PCB hydroxylation pathway were observed in HEK293CYP2A6 cells, for all three congeners tested. CYP2A6 was specifically capable of activating PCBs 28 and 101 to genotoxic metabolites which produced genetic defects which were propagated to subsequent generations, potentially contributing to carcinogenesis. In a clinical study examining CYP2A6 enzyme activity in formerly exposed individuals with elevated internal PCB levels, a participant with increased enzyme activity showed a direct association between the phenotypic activity of CYP2A6 and the metabolism of PCB28, confirming the role of CYP2A6 in the in vivo metabolism of PCB28 also in humans. These results altogether reinforce the concept that CYP2A6 plays a pivotal role in PCB congener metabolism and suggest its significance in human health, particularly in the metabolism of lower chlorinated, volatile PCB congeners.

Clinical and radiological outcome following trauma-related reverse shoulder arthroplasty.

BACKGROUND: Reverse shoulder arthroplasty (RSA) is a frequently used therapy for complex proximal humeral fractures and posttraumatic disorders. The present study's purpose was to assess the clinical and radiological outcome of primary and secondary RSA, and to analyze the impact of refixation of the greater tuberosity (GT). PATIENTS AND METHODS: 28 patients with primary fracture RSA and 18 patients with RSA due to posttraumatic disorders were examined with a mean clinical follow-up of 2.5 ± 1.73 years. Operative details and radiographs were retrospectively reviewed. Additional analyses were performed for healed and non-healed GT in primary RSA. RESULTS: Patients with fracture RSA had higher Constant-Murley score (CMS) than secondary RSA without reaching significance (p = 0.104). No significant difference was present for the quality of life measured by the Short Form 36 (SF 36) and the range of motion. In primary RSA, 78.6% GT healed anatomically. Compared to non-healed GT, patients with healed GT had a significantly higher CMS (p = 0.011), external rotation (p = 0.026) and forward flexion (p = 0.083), whereas DASH score was lower without a significant difference (p = 0.268). SF 36 showed no significant difference. Patients with healed GT had a more neutral glenoid version (p = 0.009). CONCLUSION: Superior range of motion and clinical outcome scores were present for anatomically healed GT. Therefore, refixation of the tuberosities is recommended. Secondary RSA can result in inferior results compared to primary RSA, so patients need to be adequately informed.

Ten years after: findings from the medical surveillance program on Health Effects in High-Level Exposure to PCB (HELPcB).

After the detection of high environmental and occupational exposure to polychlorinated biphenyls (PCBs) in a German recycling company for transformers and capacitors in 2010, the multidisciplinary medical surveillance program "HELPcB" (Health Effects in High-Level Exposure to PCB) was established for former PCB-exposed workers of the company, their family members, employees of surrounding companies, and area residents to investigate potential adverse health effects by PCB exposure in a longitudinal study approach with up to seven examination time points between 2010 and 2019. More than 300 individuals were enrolled into the program. Assessments particularly included plasma and urine concentrations of PCB congeners and their metabolites, clinical laboratory parameters, Comet assay, analysis of telomere length, neuropsychological examinations, psychological screening, abdominal and thyroid ultrasound examination. This review summarizes the main results of the studies conducted in the HELPcB program yielding relevant new data on potential adverse effects of PCB exposure in humans and potential mechanisms that underlie these effects. Even larger studies in PCB-exposed individuals are warranted to confirm the results of this program and to further establish causality between PCB exposure and clinical effects in humans.

Posterior shoulder dislocation with associated reverse Hill-Sachs lesion: clinical outcome 10 years after joint-preserving surgery.

INTRODUCTION: Posterior shoulder dislocation in association with reverse Hill-Sachs lesion is a rather rare injury. Few studies reporting results after joint-preserving surgery in these cases are available. This current study presents the clinical outcomes 10 years postoperatively. MATERIALS AND METHODS: In a prospective case series, we operatively treated 12 consecutive patients (all males) after posterior shoulder dislocation with associated reverse Hill-Sachs lesion using joint-preserving techniques. Patients received surgery in a single center between January 2008 and December 2011. The joint-preserving surgical procedure was chosen depending on the defect size and bone quality. The following outcome-measures were analyzed: Constant-Score, DASH-Score, ROWE-Score, and SF-12. Results 1, 5, and 10 years postoperatively were compared. RESULTS: Out of 12 patients, ten patients (83.3%) were followed-up with a mean follow-up interval of 10.7 years (range 9.3-12.8). The mean patient age at the time of the last follow-up was 51 years (32-66). The outcome scores at the final follow-up were: Constant 92.5 (range 70.0-100), DASH 3.2 (0.0-10.8), ROWE 91.0 (85.0-100), and SF-12 87.8 (77.5-98.3). Clinical results had improved from 1 to 5 years postoperatively and showed a tendency for even further improvement after 10 years. CONCLUSIONS: Joint-preserving surgical therapy of posterior shoulder dislocation provides excellent results when the morphology of the reverse Hill-Sachs lesion is respected in surgical decision-making. TRIAL REGISTRATION: 223/2012BO2, 02 August 2010.

Decomposition Products of the Initiator Bis(2,4-dichlorobenzoyl)peroxide in the Silicone Industry: Human Biomonitoring in Plasma and Urine of Workers.

Bis(2,4-dichlorobenzoyl)peroxide (2,4-DCBP) is used as an initiator for silicone rubber production. During hot curing, 2,4-DCBP decomposes into 2,4-dichlorobenzoic acid, 1,3-dichlorobenzene, and the polychlorinated biphenyl (PCB) congeners PCB-47, PCB-51, and PCB-68. The extent of occupational exposure to these decomposition products has not been investigated yet. We determined for the first time the corresponding internal exposure of employees (n = 104) of a German silicone rubber facility by human biomonitoring in plasma and urine. Collected samples were investigated by gas chromatography/mass spectrometry for levels of PCBs in plasma and by liquid chromatography/tandem mass spectrometry for urinary post-shift levels of 2,4-dichlorobenzoic acid (2,4-DCBA) and the metabolites 3,5-dichlorocatechol (3,5-DCK), 2,4-dichlorophenol (2,4-DCP), and 3,5-dichlorophenol (3,5-DCP). PCB-47 and PCB-68 levels correlated significantly and were found in >97% of all samples with maximum values of 4.43 and 0.77 µg/L, respectively. 2,4-DCBA, 3,5-DCK, 2,4-DCP, and 3,5-DCP were quantified in >80% of all urine samples with maximum levels of 1.46; 26.92; 7.68; and 0.39 mg/L, respectively. There is a considerable uptake of decomposition products of 2,4-DCBP in workers of a silicone rubber facility, affecting employees in all work areas. Individual levels depended on the work task. Considering the carcinogenic potential of PCBs, the workers' additional exposure to PCB-47 and PCB-68 might be of concern.

Welding Fume Instillation in Isolated Perfused Mouse Lungs-Effects of Zinc- and Copper-Containing Welding Fumes.

Zinc- and copper-containing welding fumes can cause systemic inflammation after exposure in humans. Recent ex vivo studies have shown that the observed inflammation originates from exposed immune cells. In vitro studies identified the soluble fraction of metal particles as the main effectors. Isolated perfused mouse lungs (IPLs) were perfused and ventilated for 270 min. Lungs were instilled with saline solution (control), welding fume particle suspension (WFs) or the soluble fraction of the welding fumes (SF-WFs). Bronchoalveolar lavage fluid (BALF) and perfusate samples were analyzed for cytokine levels and lung tissue mRNA expression levels were analyzed via RT-PCR. All lungs instilled with WFs did not complete the experiments due to a fatal reduction in tidal volume. Accordingly, IL-6 and MPO levels were significantly higher in BALF of WF lungs compared to the control. IL-6 and MPO mRNA expression levels were also increased for WFs. Lungs instilled with SF-WFs only showed mild reactions in tidal volume, with BALF and mRNA expression levels not significantly differing from the control. Zinc- and copper-containing welding fume particles adversely affect IPLs when instilled, as evidenced by the fatal loss in tidal volume and increased cytokine expression and secretion. The effects are mainly caused by the particles, not by the soluble fraction.

Longitudinal changes in telomere length in PCB-exposed individuals: interaction with CMV infection.

We recently demonstrated a significant shortening of age-adapted telomere length (TL) in lymphocytes of polychlorinated biphenyls (PCB)-exposed individuals. Here, we analyzed TL in individuals of the same PCB-exposed cohort during a 6-year follow-up period, investigating the change in TL between the first and second measurement as a function of time, concentration of PCBs and cytomegalovirus (CMV) infection. The age-adjusted TL of lymphocytes within the cohort of PCB-exposed individuals recovered from a first assessment in 2011 to a second assessment in 2017. Remarkably, if the concentration of lower chlorinated PCBs (LC PCBs) in 2011 was high (≥ 0.055 µg/L), the TL of CMV seropositive individuals remained significantly shortened both compared to age-adjusted controls as well as intra individually. This was confirmed by analysis of covariance as well as by multivariate linear mixed effects models. Since telomeres are responsive to various stress response pathways, including viral infection, we conclude that PCBs could contribute to immune senescence-like phenotypes associated with CMV infections and exacerbate negative aspects associated with the aging of the immune system.

Radiographic parameter(s) influencing functional outcomes following angular stable plate fixation of proximal humeral fractures.

PURPOSE: Radiographic parameters which correlate with poor clinical outcome after proximal humeral fractures could be helpful indicators to answer the question which patients should be followed up closer. Moreover, during surgery, radiographic parameters correlating with unfavourable outcome should be avoided. The primary aim of the study was to compare radiographic measurements between the injured and the contralateral, uninjured shoulder. The secondary aim was to correlate these radiographic parameters with post-operative shoulder function. METHODS: Fifty-eight patients (age: 55.6 ± 14.4 years, age at surgery) following angular stable plate fixation of a proximal humeral fracture (2-part fractures according to Neer: 24, 3-part: 25, 4-part: 9) were included in this retrospective cohort study. All patients were followed up at least six years (7.9 ± 1.4 after surgical intervention). During follow-up examination, the Constant score (CS) was assessed, and radiographs of both shoulders were taken. Radiographs were analyzed regarding lateral humeral offset, distance between tuberculum and head apex, head diameter, head height, perpendicular height, perpendicular center, vertical height, and angles between head and humeral shaft (CCD and HSA). These parameters were compared between the injured and uninjured shoulder. The cohort was divided in two groups: patients with a CS category of excellent/good and satisfying/worse. Both groups were tested regarding differences of demographic and radiographic parameters. RESULTS: The distance between tuberculum and head apex (2.6 ± 3.4 mm vs. 4.3 ± 2.1 mm; p = 0.0017), the CCD (123.1 ± 12.9° vs. 130.1 ± 7.3°; p = 0.0005), and the HSA (33.1 ± 12.8° vs. 40.1 ± 7.3°; p = 0.0066) were significantly smaller on the treated shoulder compared to the uninjured side. Patients reached a Constant score of 80.2 ± 17.4 (95% CI 75.6-84.8) points. Regarding outcome categories of the Constant score, 46 patients had a good to excellent outcome, and 12 patients had a satisfying or bad outcome. The comparison of these groups revealed that patients with inferior outcome in the long-term follow-up were older, female, had a more complex fracture type (AO classification), smaller lateral humeral offset, smaller head diameter and height, lower perpendicular height, and lower CCD and HSA angles. CONCLUSION: If the abovementioned parameters cannot be restored sufficiently during surgery, (reversed) shoulder arthroplasty might be a better solution to reach good post-operative outcome. Moreover, patients presenting these radiographic characteristics in the follow-up, older patients, and patients with a more complex fracture type should be followed up closer to possibly prevent poor shoulder function. TRIAL REGISTRATION: 83 250/2011BO2.

Inhibition of formyl peptide receptors improves the outcome in a mouse model of Alzheimer disease.

BACKGROUND: An important hallmark of Alzheimer's disease (AD) is the increase of Aß1-42 burden and its accumulation to senile plaques, leading the reactive gliosis and neurodegeneration. The modulation of glia cell function represents an attractive therapeutic strategy, but is currently limited by an incomplete understanding of its relevance for AD. The chemotactic G-protein coupled formyl peptide receptor (FPR), which is known to modulate Aß1-42 uptake and signal transduction, might be one candidate molecule regulating glia function in AD. Here, we investigate whether the modulation of FPR exerts beneficial effects in an AD preclinical model. METHODS: To address this question, APP/PS1 double-transgenic AD mice were treated for 20 weeks with either the pro-inflammatory FPR agonist fMLF, the FPR1/2 antagonist Boc2 or the anti-inflammatory FPR2 agonist Ac2-26. Spatial learning and memory were evaluated using a Morris water maze test. Immunohistological staining, gene expression studies, and flow cytometry analyses were performed to study neuronal loss, gliosis, and Aß-load in the hippocampus and cortex, respectively. RESULTS: FPR antagonism by Boc2-treatment significantly improved spatial memory performance, reduced neuronal pathology, induced the expression of homeostatic growth factors, and ameliorated microglia, but not astrocyte, reactivity. Furthermore, the elevated levels of amyloid plaques in the hippocampus were reduced by Boc2-treatment, presumably by an induction of amyloid degradation. CONCLUSIONS: We suggest that the modulation of FPR signaling cascades might be considered as a promising therapeutic approach for alleviating the cognitive deficits associated with early AD. Additional studies are now needed to address the downstream effectors as well as the safety profile of Boc2.

Dirty deeds done dirt cheap: sensitization of prostate cancer cells to abiraterone treatment using hydroxylated polychlorinated biphenyls.

Effective targeting of androgen biosynthesis by the 17α-hydroxylase/17,20-lyase inhibitor abiraterone prolongs survival in a variety of prostate cancer patients. However, resistance to abiraterone treatment occurs frequently and the development of new drugs supporting or complementing abiraterone therapy is urgently needed. We recently reported antiproliferative and proapoptotic effects of hydroxylated polychlorinated biphenyls (PCBs) on various blood cell lines in vitro. Here we report the biological evaluation of the PCB28 derived OH-metabolites 3-OHCB28 or 3'-OHCB28 in prostate cancer cells. Depending on concentration, both metabolites inhibit the growth of PC3 cells, a cell line representing later stages of advanced prostate cancer. In addition 3'-OHCB28 reduced the necessary concentration of abiraterone required for the inhibition of PC3 cells by a factor of 4. Western blot analysis of cytoprotective heatshock proteins (HSP) implicated a significant reduction of HSP27 expression by 3'-OHCB28 in PC3 cells. Given the known HSP27 suppressive role of abiraterone, our results therefore suggest, that that the pharmacological interaction between abiraterone and 3'-OHCB28 in PC3 cells could be produced by the combined effect of both substances on the expression of HSPs, especially the expression of HSP27. Including the known dose response linkages and pharmacokinetic characteristics of the OH-metabolites described here, we conclude, that the use of hydroxylated PCBs can be supportive for the anti-proliferative treatment of prostate cancer and merits further investigation.

[Custom-made glenoid component via 3D print : A rescue prosthetic option for patients with massive glenoid destruction and simultaneous cuff-arthropathy]. / Custom-made-Glenoidkomponente via 3D-Print : Spezielle Prothesenversorgung als finale Behandlungsoption bei massivem Glenoidaufbrauch und gleichzeitiger Rotatorenmanschetten-Defektarthropathie.

The combination of glenoid destruction with cuff arthropathy remains a challenge. A 75-year old woman presented with a post-traumatic loss of the glenoid and concomitant cuff arthropathy. Using CT-data a custom-made glenoid component was created by 3D printing. 6 months after reverse shoulder arthroplasty, the patient was free of pain with acceptable ROM. An individual glenoid component created by 3D printing is a feasible therapeutic option in patients with loss of the glenoid and concomitant cuff arthropathy.

Reactions in Tirapazamine Induced by the Attachment of Low-Energy Electrons: Dissociation Versus Roaming of OH.

Tirapazamine (TPZ) has been tested in clinical trials on radio-chemotherapy due to its potential highly selective toxicity towards hypoxic tumor cells. It was suggested that either the hydroxyl radical or benzotriazinyl radical may form as bioactive radical after the initial reduction of TPZ in solution. In the present work, we studied low-energy electron attachment to TPZ in the gas phase and investigated the decomposition of the formed TPZ- anion by mass spectrometry. We observed the formation of the (TPZ-OH)- anion accompanied by the dissociation of the hydroxyl radical as by far the most abundant reaction pathway upon attachment of a low-energy electron. Quantum chemical calculations suggest that NH2 pyramidalization is the key reaction coordinate for the reaction dynamics upon electron attachment. We propose an OH roaming mechanism for other reaction channels observed, in competition with the OH dissociation.

The androgen receptor antagonist enzalutamide induces apoptosis, dysregulates the heat shock protein system, and diminishes the androgen receptor and estrogen receptor ß1 expression in prostate cancer cells.

Enzalutamide's accepted mode of action is by targeting the androgen receptor's (AR) activity. In clinical practice, enzalutamide demonstrates a good benefit-risk profile for the treatment of advanced prostate cancer (PC), even after poor response to standard antihormonal treatment. However, since both, well-established antiandrogens and enzalutamide, target AR functionality, we hypothesized that additional unknown mechanisms might be responsible for enzalutamide's superior anticancer activity. In the current study, PC cells were incubated with enzalutamide and enzalutamide-dependent modulation of apoptotic mechanisms were assessed via Western blot analysis, TDT-mediated dUTP-biotin nick end-labeling assay, and nuclear morphology assay. Alterations of heat shock protein (HSP), AR, and estrogen receptor (ER) expression were examined by Western blot analysis. Enzalutamide attenuated the proliferation of PC cells in a time- and dose-dependent manner. In the presence of enzalutamide, apoptosis occurred which was shown by increased BAX expression, decreased Bcl-2 expression, nuclear pyknosis, and genomic DNA fragmentation. Moreover, enzalutamide inhibited the expression of HSPs primarily involved in steroid receptor stabilization and suppressed AR and ERß1 expression. This study demonstrates for the first time that enzalutamide treatment of PC cells triggers varying molecular mechanisms resulting in antiproliferative effects of the drug. In addition to the well-characterized antagonistic inhibition of AR functionality, we have shown that enzalutamide also affects the intracellular synthesis of steroid receptor-associated HSPs, thereby diminishing the expression of AR and ERß1 proteins and inducing apoptotic pathways. According to an indirect attenuation of HSP-associated factors such as steroid receptors, endometrial carcinoma, uterine leiomyosarcoma, and mamma carcinoma cells also demonstrated inhibited cell growth in the presence of enzalutamide. Our data, therefore, suggest that enzalutamide's high efficacy is at least partially independent of AR and p53 protein expression, which are frequently lost in advanced PC.

Functional and structural liver abnormalities in former PCB exposed workers - analyses from the HELPcB cohort.

The effects of polychlorinated biphenyls (PCB) on liver function and structure are still under debate. Although higher transaminase activity and tumor promoting potential of PCB reported for animal and human studies was suggested, these studies were not able to provide definitive evidence on the ability of these chemicals to affect liver function and contribution to tumor development. The aim of this study was to determine the influence of PCB on liver function and morphology in a cohort of former PCB exposed workers. Over 5 years, a longitudinal analysis of the association between PCB concentration and hepatic transaminases such as alanine transaminase (ALT) aspartate amino transaminase (AST) and gamma glutamyltransferase (γGT), as well as liver size and structure was undertaken. Data demonstrated a significant inverse association between PCB concentration and γGT activity levels but there was no marked relationship with AST and ALT activities. Regarding sonographic examination, a significant association was found between liver size and PCB concentration. This association remained, even after adjusting for alcohol consumption, liver affecting drugs, timespan of internal exposure, or age. No marked correlation was noted between PCB concentration and liver structure changes. In summary, an association was observed between PCB concentration and γGT activity levels as well as liver size in humans. The long-term health consequences attributed to PCB on liver and in particular in tumorigenesis are not foreseeable in our cohort thus far, but remain a focus in further ongoing surveillance.

Evaluation of the Constant score: which is the method to assess the objective strength?

BACKGROUND: The Constant score (CS) is one of the most frequently applied tools for the assessment of the shoulder joint. However, evaluation of strength is not standardized leading to potential bias when comparing different studies. METHODS: Seventy-six patients with fractures of the proximal humerus undergoing open reduction and internal fixation (ORIF) were assessed using standardized CS strength measurements at the deltoid muscle insertion and at the wrist in three different arm positions. Variation coefficients were evaluated for each patient and position. RESULTS: Forty women (57%) and 36 men (43%) were examined 96 months in mean after ORIF. We could state a maximum of 105.3 N difference if measurements were performed at the wrist or the insertion of the deltoid muscle in 90° forward flexion on the injured arm (167.9 ± 83.1 N; 62.6 ± 29.4 N). The lowest variation coefficient of the three performed measurements could be stated at the deltoid muscle insertion in a 90° abduction position in the scapula plane (6.94 ± 5.5). CONCLUSION: Following our study results, different positions of force measurement can change the total CS by a whole category (e.g. "very good" to "good"). We recommend performing the measurement at the insertion of the deltoid muscle in a 90° abduction position in the scapula plane. Otherwise, even in the non-injured, it is hard to reach a "normal" shoulder function, based on the CS. When using the CS as outcome parameter, authors must give detailed information about the force measuring and use an exact measuring device.

Influence of Telomere Length in Hepatocytes on Liver Regeneration after Partial Hepatectomy in Rats.

BACKGROUND: The aim of this study was to investigate telomere length in hepatocytes as a biomarker for liver regeneration after partial hepatectomy (PH) in rats. MATERIALS AND METHODS: Sixty male Wistar rats underwent a 70% PH. One-month-old rats were assigned to group Y (n = 30) and 4-month-old rats were assigned to group O (n = 30). The rats were euthanized, and their livers were then harvested at postoperative day (POD) 1, 2, 3, 4, or 7. Telomere lengths and established parameters for liver regeneration (residual liver weight and levels of proliferating cell nuclear antigen [PCNA], Ki67, and interleukin [IL]-6) were measured. RESULTS: We observed a significant increase in residual liver weight in group Y compared to that in group O (p = 0.001). The levels of Ki67 (p = 0.016), PCNA (p < 0.0001), and IL-6 (p < 0.001) were significantly higher in group Y. Furthermore, the rats in group Y had significantly earlier peak values of Ki67 and PCNA. Telomeres were significantly longer at the time of PH in group Y (p = 0.001). We showed a correlation between telomere length at the day of PH and liver regeneration. Animals with longer telomeres at the time of PH had better liver regeneration (p = 0.015). In group Y, animals with increased liver regeneration (median cut-off: > 122%) did not show any significant difference in telomere length (p = 0.587) compared to rats with regular regeneration (< 122%). However, in the older animals, rats with increased regeneration had significantly longer telomeres (p = 0.019) than rats with regular regeneration. CONCLUSION: Telomere length in rat hepatocytes depends on age, and animals with long telomeres had earlier and better regeneration of healthy liver tissue than rats with short telomeres. Our data confirms that telomere length in rat hepatocytes could be used as a possible predictive marker for liver regeneration, and could help to identify older individuals with a high capacity for hepatic regeneration.

Telomere shortening in enterocytes of patients with uncontrolled acute intestinal graft-versus-host disease.

Acute intestinal graft-versus-host disease (aGVHD) refractory to immunosuppressive treatment is a serious complication after allogenic hematopoietic stem cell transplantation (HSCT). The underlying mechanisms of refractory aGVHD of the gut are not fully understood. Although telomere length (TL) reflects the replicative history of a cell, critically short telomeres have been associated with replicative exhaustion and tissue failure. In this study, we demonstrate that enterocytes of patients with refractory intestinal aGVHD show significantly increased proliferation, which translates into significant and critical telomere attrition following HSCT as compared with unaffected patients undergoing HSCT. Calculated telomere loss in aGVHD patients is 190 bp/wk, thereby massively exceeding physiological steady-state TL shortening rates such as in lymphocytes (∼50 bp/y). Our data support the hypothesis that increased compensatory proliferation following continued tissue damage can result in massive telomere loss in enterocytes of aGVHD patients. The present study introduces aGVHD-triggered increased cellular turnover and telomere loss with subsequent replicative exhaustion as a mechanism for refractory gut GVHD that is compatible with the long-term clinical aspect of the disease and provides a basis for stem cell protective therapies in the treatment of aGVHD.

Evidence for a pre-existing telomere deficit in non-clonal hematopoietic stem cells in patients with acute myeloid leukemia.

Telomere shortening represents an established mechanism connecting aging and cancer development. We sequentially analyzed telomere length (TL) of 49 acute myeloid leukemia (AML) patients at diagnosis (n = 24), once they achieved complete cytological remission (CCR) and/or during refractory disease or relapse and after 1-year follow-up, with all patients having at least two sequential samples. TL was analyzed by monochrome multiplex quantitative polymerase chain reaction. We have observed substantially shortened TL in the cells of patients at diagnosis compared to age-adjusted controls. In patients reaching CCR after chemotherapy, telomere shortening was less pronounced than in persistence or relapse but still significantly shortened compared to controls. We estimate patients harboring approximately 20 years of premature telomere loss compared to healthy aged-matched subjects at the time of AML onset. Our data indicate a pre-existing telomere deficit in non-clonal hematopoiesis of AML patients providing a link between age and AML development.

Accelerated telomere shortening in peripheral blood lymphocytes after occupational polychlorinated biphenyls exposure.

Polychlorinated biphenyls (PCBs) are organochlorine pollutants with a worldwide dissemination. We examined telomere length (TL) in peripheral blood cells of 207 individuals with a high body burden of PCBs due to occupational exposure in a transformer recycling company. Whereas TL in granulocytes was not affected, the age-adjusted TL in lymphocytes (∆TLLymph) of exposed individuals was significantly shorter than expected [-0.77 kb; 95 % confidence interval (CI) -0.9316; -0.6052; p = 0.0001]. PCB exposure did not affect lymphocyte numbers or T cell receptor excision circle (TREC) levels in T cells, suggesting that PCBs cause loss of telomeric DNA in T cells due to their metabolic activation and antigen-stimulated proliferation. In support of this hypothesis, blood plasma levels of PCB-exposed individuals inhibited expression of telomerase, the telomere elongating enzyme in vitro in antigen-specific T cell proliferation assays. 3-OH-CB28, a downstream metabolite of the lower chlorinated PCB-28 in PCB-exposed individuals (mean blood plasma concentration: 0.185 ± 0.68 ng/mL), inhibited telomerase gene expression within 48 h of incubation in lymphoproliferative assays starting at a concentration of 0.27-6.75 µg/mL and accelerated telomere shortening in long-term cell culture experiments. Accelerated telomere shortening due to PCB exposure may lead to limitations of cell renewal and clonal expansion of lymphocyte populations. As PCB-related immune dysfunctions have been linked to increased susceptibility to infectious diseases and increased risk of cancer, our data provide a possible explanation, for how PCBs could promote infections and cancer through limiting immune surveillance.