Molecular pathology of pulmonary surfactants and cytokines in drowning compared with other asphyxiation and fatal hypothermia

Oxidative stress and NF-KB/iNOS inflammatory pathway as innovative biomarkers for diagnosis of drowning and differentiating it from postmortem submersion in both fresh and saltwater in rats

BACKGROUND

Finding a dead body in water raises an issue concerning determining the cause of death as drowning because of the complex pathophysiology of drowning. In addition, the corpse may be submersed postmortem.

OBJECTIVE

Evaluate the role of oxidative stress markers and NF-KB/iNOS inflammatory pathway as diagnostic biomarkers in drowning and whether they could differentiate freshwater from saltwater drowning.

METHODS

This study included forty-five adult male albino rats classified into five groups: control group (C), Freshwater-drowned group (FD), Freshwater postmortem submersion group (FPS), saltwater-drowned group (SD), and saltwater postmortem submersion group (SPS). After the autopsy, the rats' lungs in each group were prepared for histological, immunohistochemical (caspase 3, TNF-α, NF-kB, COX-2 & iNOS), biochemical studies; MDA, NOx, SOD, GSH, VCAM-1, COX-2; and RT-PCR for the relative quantification of NF-kB and iNOS genes expression.

RESULTS

Lung oxidative markers were significantly affected in drowned groups than in postmortem submersion groups. Inflammatory pathway markers were also significantly increased in the drowned groups, with concern that all markers were significantly affected more in saltwater than in freshwater drowned group.

CONCLUSIONS

It is concluded that the tested markers can be used accurately in diagnosing drowning and differentiating it from postmortem submersion with a better understanding of the mechanism of death in drowning as both mechanisms, inflammatory and oxidative stress, were revealed and involved.

Impact of lifeguard oxygen therapy on the resuscitation of drowning victims: Results from an Utstein Style for Drowning Study

INTRODUCTION

No published evidence was identified regarding the use of oxygen in the treatment of drowning in two recent systematic reviews. The aim of our study was to investigate the impact of on scene, pre-Emergency Medical Services (EMS) oxygen therapy by lifeguards in the resuscitation of drowning victims.

METHOD

We conducted a retrospective case match analysis of drowning patients presenting to the EDs of Sunshine Coast Hospital and Health Service. Patients were matched for age, sex and severity of drowning injury. The primary outcome was in-hospital mortality. Secondary outcomes included positive pressure ventilation (PPV) by EMS and the ED, as well as admission to the Intensive Care Unit.

RESULTS

There were 108 patients in each group. Median (IQR) age was 22 (15-43) in the oxygen group and 23 (15-44) years in the non-oxygen group. There were 45 females in the oxygen group and 41 females in the non-oxygen group. Sixteen patients had suffered cardiac arrest and three patients respiratory arrest in each group. There were five deaths in each group. Initial oxygen saturation on arrival of EMS was identical in both groups 89.2% (±19.9) in the oxygen group versus 89.3% (±21.1) (P = 0.294) in the non-oxygen group. The oxygen group required PPV more frequently with EMS (19 vs 11, P < 0.01) and in the ED (19 vs 15, P < 0.01).

CONCLUSION

On scene treatment with oxygen by lifeguards did not improve oxygenation or outcomes in drowning patients.

Effects of Prolactin on Brain Neurons under Hypoxia

The levels and potential role of prolactin (PRL) in the brain under conditions of acute systemic hypoxia were examined, focusing on the accumulation of PRL in cerebrospinal fluid (CSF) and its effects on neuronal activity and injury. The amount of PRL in the brain was investigated using brain tissues from forensic autopsy cases. We counted the number of neurites that formed in human primary neurons (HNs) after the addition of PRL. Furthermore, HNs supplemented with PRL or triiodothyronine (T3) were exposed to hypoxic conditions, and the dead cells were counted. The results showed correlations between brain PRL and CSF PRL levels. Additionally, PRL accumulation in the brain was observed in cases of asphyxia. In vitro experimental findings indicated increased neurite formation in the HNs treated with PRL. Moreover, both PRL and T3 demonstrated neuroprotective effects against hypoxia-induced neuronal cell death, with PRL showing stronger neuroprotective potential than T3. These results suggest that PRL accumulates in the brain during hypoxia, potentially influences neuronal activity, and exhibits neuroprotective properties against hypoxia-induced neuronal injury.

Quantitative estimation of TNF-α and IL-3 by using ELISA from human lung tissue in fatal asphyxial deaths

Asphyxia-related deaths have always been a challenging task in the specialty of forensic pathology. Apart from helpful macroscopical signs (e.g., strangulation marks, cyanosis, petechial haemorrhage, and lung edema), recent literature indicates that prolonged asphyxia is sufficient to induce an increase in mast cells (MC). Inflammatory cells migrate from the bone marrow to the lungs, aiding in the diagnosis of fatal asphyxial death. The present study analyzed human lung tissue samples from 90 medico-legal autopsy cases, including 45 asphyxial deaths and 45 controls (non-asphyxial deaths). The cases ranged from 2 to 68 years, with a mean age of 33.23 years. In 90 cases, 74 cases were of males, and 16 were of females. Human lung tissue samples were analyzed by using the sandwich ELISA method. The results indicated a statistically significant increase in TNF-α and IL-3 concentration in fatal asphyxial deaths, including those caused by hanging, drowning, and smothering. Mean ± SD in asphyxial and non-asphyxial cases for the TNF-α and IL-3 concentration statistically analysed. In asphyxial cases, the average IL-3 concentration (Conc.) was 1558.50 ± 350.53 pg/ml, and the average TNF-α concentration (Conc.) was 499.75 ± 479.41 pg/ml. In contrast, in non-asphyxial cases, the average IL-3 concentration (Conc.) was found to be 849.73 ± 484.99 pg/ml, and the average TNF-α concentration (Conc.) was 208.08 ± 81.23 pg/ml. The mean change in IL-3 and TNF-α (Conc.) values are found to significant (<0.01) in asphyxial cases as compared to non-asphyxial cases. The ROC (Receiver operating characteristic curve) analysis revealed that TNF-α (AUC = 0.89) and IL-3 (AUC = 0.87) concentration (conc.) were stronger predictors of asphyxial deaths with an optimal cut-off value of 455.20 pg/ml for TNF-alpha and 1700.62 pg/ml for IL-3 respectively. Our findings imply that mast cells (MC) are critical in fatal hypoxia-related mortality and that TNF-α and IL-3 can be reliable markers for detecting mast cells in asphyxial deaths. It could be very beneficial to forensic pathologists tasked with differentiating fatal asphyxial fatalities from other causes of death.

Relationship between clock gene expression and CYP2C19 and CYP3A4 with benzodiazepines

The present study aimed to clarify the expressions and roles of clock genes involved in drug metabolism in patients taking benzodiazepines (BZDs), as well as the drug metabolism regulators controlled by clock genes for each BZD type. The relationships between the expressions of the clock genes BMAL1, PER2, and DBP and the drug-metabolizing enzymes CYP3A4 and CYP2C19 were investigated using livers from BZD-detected autopsy cases. In addition, the effect of BZD exposure on various genes was examined in HepG2 human hepatocellular carcinoma cells. The expressions of DBP, CYP3A4, and CYP2C19 in the liver were lower in the diazepam-detected group than in the non-detected group. Furthermore, BMAL1 expression correlated with CYP2C19 expression. Cell culture experiments showed that the expressions of DBP and CYP3A4 decreased, whereas those of BMAL1 and CYP2C19 increased after diazepam and midazolam exposure. The results of the analyses of autopsy samples and cultured cells suggested that DBP regulates CYP3A4 when exposed to BZD. Understanding the relationship between these clock genes and CYPs may help achieve individualized drug therapy.

Effect of methamphetamine on clock genes and drug-metabolizing enzyme expression

This study examined the association between clock gene expression and the effect of methamphetamine (MA) on drug-metabolizing enzymes from the perspective of drug metabolism. The relationship between expression of the clock genes BMAL1 and PER2 and the drug-metabolizing enzymes CYP3A4 and CYP2D6 was investigated using livers from autopsy cases of MA-intoxication deaths. Additionally, the effect of MA exposure on various genes was examined in HepG2 human hepatocellular carcinoma cells. Comparisons of the expression of various genes in MA users according to blood MA concentration revealed that CYP3A4 expression was similar to that of PER2, and CYP2D6 expression was similar to that of BMAL1. In cultured cell experiments, BMAL1 and CYP2D6 expression decreased depending on the time elapsed after MA addition, and PER2 and CYP3A4 expression increased slightly in a concentration-dependent manner. These results were consistent with the findings of autopsy examinations. Expression of CYP3A4 and CYP2D6 under BMAL1 and PER2 suppression, but not CYP2D6 under PER2 suppression alone, was upregulated in response to MA. These results suggest that CYPs are regulated via the clock genes BMAL1 and PER2 during MA metabolism.

Trace elements in forensic human lung: A new approach to the diagnosis of seawater drowning. A preliminary study

The diagnosing of drowning remains one of the most challenging activities for the forensic pathologist. There is little information on the impact on the lung as a target organ in death by drowning. We aimed to investigate the concentration of trace elements in the lungs of people who had suffered different types of death to evaluate the discriminating ability of trace elements to identify seawater drowning (SWD). A total of 11 trace elements were analyzed by Inductively Coupled Plasma-Mass Spectrometry in 74 forensic cases. Sampler scanning electron microscopy and Energy Dispersive X-ray spectroscopy (EDX) were used to identify ultrastructural lung alterations. A Principal Component Analysis (PCA) of trace elements was carried out. The trace elements in SWD lungs were detected in the following order of concentration: Br˃Zn˃Sr˃Cr˃Cu˃As˃Pb˃Se˃Mn˃Ni˃Cd. Our results showed significantly higher concentrations of Br and Sr (P = 0.010 and P = 0.000) and significantly lower concentrations of Zn, Pb, Cu, Cd, and Se in SWD compared with other causes of death. After adjusting by confounder factors, Sr and Br remained as predictive independent factors for diagnosis of drowning (p = 0.042, in both cases). These results were confirmed by PCA, which revealed a wide separation between SWD and the rest of the causes of death. Our SWD cohort was characterized by high concentrations of the trace elements Br and Sr and low concentrations of Zn, Pb, Cu, Cd, and Se in lung tissue, while PCA showed its discriminatory capacity to identify death by seawater drowning. These findings, together with those obtained using other techniques, can be of great importance in the diagnosis of SWD.

The Impact of Donor Asphyxiation or Drowning on Pediatric Lung Transplant Recipients

BACKGROUND

Donors with drowning or asphyxiation (DA) as a mechanism of death (MOD) are considered high risk in pediatric lung transplantation. We sought to evaluate whether recipients of DA donors had negatively impacted outcomes.

METHODS

Pediatric recipients recorded in the United Network for Organ Sharing registry between 2000 and 2019 were included. Primary stratification was donor MOD. Propensity matching with a 1:1 ratio was performed to balance the DA and non-DA MOD donor cohorts. Cox multivariable regression was used to determine the risk-adjusted impact of donor MOD. A subanalysis of the effect of lung allocation score was also evaluated.

RESULTS

A total of 1016 patients underwent bilateral lung transplantation during the study period, including 888 (85.6%) from non-DA donors and 128 (14.4%) from DA donors. Survival at 90 days, 1 year, and 2 years were similar in the matched and unmatched cohorts regardless of the donor MOD. Moreover, separate risk-adjusted analysis of drowning and asphyxiated donors was similar to other MOD donors at 30 days, 1 year, and 5 years. Similar survival findings persisted regardless of pretransplant lung allocation score. Although the rates of posttransplant stroke (1.0% versus 3.1%, P = 0.04) and the length of hospital stay (19 versus 22 d, P = 0.004) were elevated in the unmatched DA MOD recipients, these differences were mitigated after propensity matching.

CONCLUSIONS

This study evaluated the impact of DA MOD donors in pediatric lung transplant recipients and found similar rates of complications and survival in a propensity-matched cohort. These data collectively support the consideration of DA MOD donors for use in pediatric lung transplantation.

Determining the effect of water temperature on the T1 and T2 relaxation times of the lung tissue at 9.4 T MRI: A drowning mouse model

Japanese individuals have a unique culture of soaking in a bathtub, and forensic pathologists have experienced fatal cases due to drowning. However, T1 and T2 relaxation times of a drowning lung are poorly documented. In the present study, we investigated the relationship between drowning water temperature and T1 and T2 relaxation times of drowning lung tissues at 9.4 T MRI (Bruker, BioSpec94/20USR). The mice used as animal drowning models were directly submerged in freshwater. Water temperature was set to 8 °C-10 °C (cold), 20 °C-22 °C (normal), 30 °C, and 45 °C. The regions of interest (ROIs) on the axial section of the third slice were set at the central and peripheral areas of each-the left and the right-lung. T1 relaxation times measured immediately after death differed by the presence or absence of soaking water, except in case of cold water temperature. In the drowning groups, T1 relaxation time showed a linear dependency on water temperature. By contrast, T2 relaxation time was almost constant regardless of the presence of drowning under the same temperature condition; when compared in the lung areas of the same individuals, the times were uniformly reduced in drowning models. To minimize the effects of hypostasis and decomposition, we performed measurements immediately after death and were able to determine the noticeable difference in drowning water temperature. These results may be useful for qualitative assessments of a drowning lung and may serve as a basis when imaging the human body during forensic autopsy cases.

MicroRNAs: An Update of Applications in Forensic Science

MicroRNAs (miRNAs) are a class of non-coding RNAs containing 18–24 nucleotides that are involved in the regulation of many biochemical mechanisms in the human body. The level of miRNAs in body fluids and tissues increases because of altered pathophysiological mechanisms, thus they are employed as biomarkers for various diseases and conditions. In recent years, miRNAs obtained a great interest in many fields of forensic medicine given their stability and specificity. Several specific miRNAs have been studied in body fluid identification, in wound vitality in time of death determination, in drowning, in the anti-doping field, and other forensic fields. However, the major problems are (1) lack of universal protocols for diagnostic expression testing and (2) low reproducibility of independent studies. This review is an update on the application of these molecular markers in forensic biology.

DNA microarray analysis of hypothermia-exposed murine lungs for identification of forensic biomarkers

We used DNA microarray technology to analyze the pulmonary transcriptome of mice killed by hypothermia. This analysis identified significant differential regulation of 4094 genes; specifically, 1699 genes were upregulated, and 2395 were downregulated in response to hypothermia. The gene encoding cathelicidin antimicrobial peptide was the most upregulated gene, and that encoding BAI1-associated protein 2-like 1 was the most downregulated. Gene-set analysis identified significant hypothermia-induced variations in 101 pathways, and we discovered that pathways related to immunity are involved in the pulmonary pathogenesis of hypothermia. The present findings demonstrate some of the acute pulmonary responses to hypothermia and indicate several pulmonary genes as candidate forensic biomarkers of hypothermia. Furthermore, the present findings suggest that host defense is induced in hypothermic lungs. The present microarray data may facilitate the development of protein analyses for human forensics by immunohistochemistry, western blotting and enzyme-linked immunosorbent assay and may be beneficial in clinical research of hypothermia.

Thyroid-related hormones as potential markers of hypoxia/ischemia

This study aimed to investigate the usefulness of the thyroid-related hormones as markers of acute systemic hypoxia/ischemia to identify deaths caused by asphyxiation due to neck compression in human autopsy cases. The following deaths from pathophysiological conditions were examined: mechanical asphyxia and acute/subacute blunt head injury; acute/subacute non-head blunt injury; sharp instrument injury as the hemorrhagic shock condition; drowning as alveolar injury; burn; and death due to cardiac dysfunction. Blood samples were collected from the left and right cardiac chambers and iliac veins, and serum triiodothyronine (T3), thyroxine (T4), thyroglobulin (Tg), and thyroid-stimulating hormone (TSH) levels were measured using electrochemiluminescence immunoassays. Two types of thyroid cell lines were used to confirm independent thyroid function under the condition of hypoxia (3% O₂). The human thyroid carcinoma cell line (HOTHC) cell line derived from human anaplastic thyroid carcinoma and the UD-PTC (sample of the second resection papillary thyroid carcinoma) cell line derived from human thyroid papillary adenoma, which forms Tg retention follicles, were used to examine the secretion levels of T3, T4, and Tg hormones. The results showed a strong correlation between T3 and T4 levels in all blood sampling sites, while the TSH and Tg levels were not correlated with the other markers. Serum T3 and T4 levels were higher in cases of mechanical asphyxia and acute/subacute blunt head injury, representing hypoxic and ischemic conditions of the brain as compared to those in other causes of death. In the thyroid gland cell line, T4, T3, and Tg levels were stimulated after exposure to hypoxia for 10-30 min. These findings suggest that systemic advanced hypoxia/ischemia may cause a rapid and TSH-independent release of T3 and T4 thyroid hormones in autopsy cases. These findings demonstrate that increased thyroid-related hormone (T3 and T4) levels in the pathophysiological field may indicate systemic hypoxia/ischemia.

Drowning in fresh or salt water: respective influence on respiratory function in a matched cohort study

INTRODUCTION

For the most severe drowned patients, hypoxemia represents one of the major symptoms. As the influence of the type of water (fresh or salt water) on respiratory function is still unclear, the primary endpoint of this multicenter study was to compare hypoxemia according to the type of water.

METHODS

Medical records of adult patients who experienced a drowning event and were consequently admitted to 10 ICU for acute respiratory failure were analyzed retrospectively using data collected over three consecutive summer periods. From an initial cohort of acute respiratory failure drowned patients, patients were matched by age, sex, Glasgow Coma Scale, and occurrence of cardiac arrest (yes or no).

RESULTS

Among an initial cohort of 242 patients, 38 pairs were matched correctly. At the initial assessment, carried out upon ICU admission, hypoxemia was found to be deeper in the fresh water group (PaO2/FiO2: 141 ± 76 vs. 220 ± 122, P < 0.05). However, there was no significant difference in tissue oxygenation (assessed by blood lactate level) between groups. In terms of biology results, sodium levels were higher in the salt water group in the initial assessment (144 ± 6.8 vs. 140 ±5.2 mmol/l, P = 0.004), but no difference was observed later. No difference was recorded in the outcome or length of stay in ICU between groups.

CONCLUSION

Drowning in fresh water was associated with deeper hypoxemia in the initial assessment. Despite this initial difference, latter respiratory and biological parameters or outcome were similar in both groups.

Postmortem Diagnosis of Fatal Hypothermia by Fourier Transform Infrared Spectroscopic Analysis of Edema Fluid in Formalin-Fixed, Paraffin-Embedded Lung Tissues

The goal of this study was to investigate whether pulmonary edema could become a specific diagnostic marker for fatal hypothermia using Fourier transform infrared (FTIR) spectroscopy in combination with chemometrics. The spectral profile analysis indicated that hypothermia fatalities associated with pulmonary edema fluid contained more β-sheet protein conformational structures than the control causes of death, which included sudden cardiac death, brain injury, cerebrovascular disease, mechanical asphyxiation, intoxication, and drowning. Subsequently, the results of principal component analysis (PCA) further revealed that the content of β-sheet protein conformational structures in the pulmonary edema fluid was the main discriminatory marker between fatal hypothermia and the other causes of death. Ultimately, a robust postmortem diagnostic model for fatal hypothermia using a partial least-squares discriminant analysis (PLS-DA) algorithm was constructed. Pulmonary edema fluid spectra collected from eight new forensic autopsy cases that did not participate in the construction of the diagnostic model were predicted using the model. The results showed the causes of death of all these eight cases were correctly classified. In conclusion, this preliminary study demonstrates that FTIR spectroscopy in combination with chemometrics could be a promising approach for the postmortem diagnosis of fatal hypothermia.

Postmortem chest computed tomography for the diagnosis of drowning: a feasibility study

It may be difficult to distinguish the cause of death in drowning cases without specific findings. The aim of this study was to explore the forensic value of thoracic postmortem computed tomography (PMCT) using routine images and three-dimensional (3D) image reconstructions. The imaging data of PMCT examinations of six drowning cadavers, aged 21–54 years, were analyzed. Twelve victims of sudden death from coronary artery disease (CAD) were chosen as a control group. After 3D bilateral lung images were reconstructed using image processing software, an interactive medical image control system was used to measure and analyze parameters including lung volume, lung volume ratio, mean CT value of the whole lung, and lung CT value distribution curves. Lung volume and lung volume ratio were used to assess the shape changes of the lung. Lung CT value distribution curves showed the corresponding number of pixels of the different CT values in the lung image. Lung volume was not significantly larger in drowning cases (mean 2 958 cm³) than in controls (mean 2 342 cm³). Lung volume ratio values in the drowning group (mean 0.3156) were greater than those in the control group (mean 0.2763); (P = 0.02). There was no significant difference between the drowning and control group in the mean CT value of the whole lung. There were differences between lung CT value distribution curves in drowning victims and controls, with drowning victims showing a single peak and CAD cases showing a bimodal distribution. Thoracic PMCT is helpful for the forensic medical diagnosis of drowning. Lung volume ratio and lung CT value distribution are potential indicators to distinguish between drowning and CAD.

Potential forensic application of receptor for advanced glycation end products (RAGE) and aquaporin 5 (AQP5) as novel biomarkers for diagnosis of drowning

Drowning is the most common cause of unnatural death worldwide. There is no single biomarker to diagnose drowning, so the diagnosis of drowning is one of the most difficult tasks in forensic medicine. Especially, distinguishing a victim of drowning from a body disposed of in water following death remains a problem. The objective of this study was to identify specific biomarkers of drowning compared with other causes of death such as hypoxia and postmortem submersion. The present study investigated the intrapulmonary expression of receptor for advanced glycation end products (RAGE), aquaporin-5 (AQP5), surfactant protein-A (SP-A), interleukin 6 (IL-6) and interleukin 1β (IL-1β) as markers of drowning. In animal experiments, all rats (n = 45) were classified into four groups (drowning, postmortem-submersion, hypoxia and control group). The lungs of experimental animals were analyzed as mRNA expression, immunoblot expression and immunohistochemical staining. qRT-PCR demonstrated increased mRNA expression of RAGE and AQP5 in drowning group compared with that in control, hypoxia and postmortem-submersion group, but not other molecules. Western blotting also showed high expression of RAGE and AQP5 in drowning group, immunostaining of RAGE and AQP5 was highly detected in a linear pattern in type I alveolar epithelial cells, compared with control and postmortem-submersion group. These observations indicate a difference of expression in pulmonary molecular pathology compared with other causes, suggesting RAGE and AQP5 may be useful for differentiation between drowning and postmortem-submersion.

Comprehensive Histological and Immunochemical Forensic Studies in Deaths Occurring in Custody

In-custody deaths have several causes, and these include homicide, suicide, natural death from chronic diseases, and unexplained death possibly related to acute stress, asphyxia, excited delirium, and drug intoxication. In some instances, these deaths are attributed to undefined accidents and natural causes even though there is no obvious natural cause apparent after investigation. Understanding these deaths requires a comprehensive investigation, including documentation of circumstances surrounding the death, review of past medical history, drug and toxicology screens, and a forensic autopsy. These autopsies may not always clearly explain the death and reveal only nonspecific terminal events, such as pulmonary edema or cerebral edema. There are useful histologic and biochemical signatures which identify asphyxia, stress cardiomyopathy, and excited delirium. Identifying these causes of death requires semiquantitative morphologic and biochemical studies. We have reviewed recent Bureau of Justice Statistics on in-custody death, case series, and morphological and biochemical studies relevant to asphyxia, stress cardiomyopathy, and excited delirium and have summarized this information. We suggest that regional centers should manage the investigation of these deaths to provide more comprehensive studies and to enhance the expertise of forensic pathologists who would routinely manage potentially complex and difficult cases.

Physiology Of Drowning: A Review

Drowning physiology relates to two different events: immersion (upper airway above water) and submersion (upper airway under water). Immersion involves integrated cardiorespiratory responses to skin and deep body temperature, including cold shock, physical incapacitation, and hypovolemia, as precursors of collapse and submersion. The physiology of submersion includes fear of drowning, diving response, autonomic conflict, upper airway reflexes, water aspiration and swallowing, emesis, and electrolyte disorders. Submersion outcome is determined by cardiac, pulmonary, and neurological injury. Knowledge of drowning physiology is scarce. Better understanding may identify methods to improve survival, particularly related to hot-water immersion, cold shock, cold-induced physical incapacitation, and fear of drowning.

Identification of distinct genes associated with seawater aspiration‑induced acute lung injury by gene expression profile analysis

Seawater aspiration-induced acute lung injury (ALI) is a syndrome associated with a high mortality rate, which is characterized by severe hypoxemia, pulmonary edema and inflammation. The present study is the first, to the best of our knowledge, to analyze gene expression profiles from a rat model of seawater aspiration-induced ALI. Adult male Sprague-Dawley rats were instilled with seawater (4 ml/kg) in the seawater aspiration-induced ALI group (S group) or with distilled water (4 ml/kg) in the distilled water negative control group (D group). In the blank control group (C group) the rats' tracheae were exposed without instillation. Subsequently, lung samples were examined by histopathology; total protein concentration was detected in bronchoalveolar lavage fluid (BALF); lung wet/dry weight ratios were determined; and transcript expression was detected by gene sequencing analysis. The results demonstrated that histopathological alterations, pulmonary edema and total protein concentrations in BALF were increased in the S group compared with in the D group. Analysis of differential gene expression identified up and downregulated genes in the S group compared with in the D and C groups. A gene ontology analysis of the differential gene expression revealed enrichment of genes in the functional pathways associated with neutrophil chemotaxis, immune and defense responses, and cytokine activity. Kyoto Encyclopedia of Genes and Genomes analysis revealed that the cytokine-cytokine receptor interaction pathway was one of the most important pathways involved in seawater aspiration-induced ALI. In conclusion, activation of the cytokine-cytokine receptor interaction pathway may have an essential role in the progression of seawater aspiration-induced ALI, and the downregulation of tumor necrosis factor superfamily member 10 may enhance inflammation. Furthermore, IL-6 may be considered a biomarker in seawater aspiration-induced ALI.

Postmortem biochemistry: Current applications

The results of biochemical analyses in specimens obtained postmortem may aid death investigation when diabetic and alcoholic ketoacidosis is suspected, when death may have been the result of drowning, anaphylaxis, or involved a prolonged stress response such as hypothermia, and in the diagnosis of disease processes such as inflammation, early myocardial infarction, or sepsis. There is often cross-over with different disciplines, in particular with clinical and forensic toxicology, since some endogenous substances such as sodium chloride, potassium chloride, and insulin can be used as poisons. The interpretation of results is often complicated because of the likelihood of postmortem change in analyte concentration or activity, and proper interpretation must take into account all the available evidence. The unpredictability of postmortem changes means that use of biochemical measurements in time of death estimation has little value. The use of vitreous humour is beneficial for many analytes as the eye is in a physically protected environment, this medium may be less affected by autolysis or microbial metabolism than blood, and the assays can be performed with due precaution using standard clinical chemistry analysers. However, interpretation of results may not be straightforward because (i) defined reference ranges in life are often lacking, (ii) there is a dearth of knowledge regarding, for example, the speed of equilibration of many analytes between blood, vitreous humour, and other fluids that may be sampled, and (iii) the effects of post-mortem change are difficult to quantify because of the lack of control data. A major limitation is that postmortem vitreous glucose measurements are of no help in diagnosing antemortem hypoglycaemia.

Forensic application of microRNA-706 as a biomarker for drowning pattern identification

Forensic research using microRNA has been used so far only for the identification of body fluids, but its use in understanding biological processes in post-mortem pathology has not been studied before. Therefore, we performed experiments in mice to compare between freshwater and saltwater drowning models, and miRNA expression was analyzed in the brain through a forward bioinformatics screening approach. In this study, we identified eight specific microRNAs whose expression increased in freshwater and decreased in saltwater. Among them, miR-706 - targeting HCN1 - was identified as a potent biomarker for the drowning pattern identification. A higher expression of miR-706 was detected in the freshwater drowning compared to the control and saltwater drowning group (p<0.05, and p<0.01, respectively). HCN1 mRNA expression, a suggested candidate target for miR-706, was lower in the freshwater (p<0.01) than in the saltwater drowning group, and showed statistical difference between freshwater and saltwater drowning (p<0.01). miR-706 was specifically expressed in the hippocampal neurons as detected by in situ hybridization. Our data suggest that a specific microRNA may provide clues to understanding some crime scene investigations and pathobiological processes in the dead body.

Postmortem mRNA expression patterns in left ventricular myocardial tissues and their implications for forensic diagnosis of sudden cardiac death

Sudden cardiac death (SCD), which is primarily caused by lethal heart disorders resulting in structural and arrhythmogenic abnormalities, is one of the prevalent modes of death in most developed countries. Myocardial ischemia, mainly due to coronary artery disease, is the most common type of heart disease leading to SCD. However, postmortem diagnosis of SCD is frequently complicated by obscure histological evidence. Here, we show that certain mRNA species, namely those encoding hemoglobin A1/2 and B (Hba1/2 and Hbb, respectively) as well as pyruvate dehydrogenase kinase 4 (Pdk4), exhibit distinct postmortem expression patterns in the left ventricular free wall of SCD subjects when compared with their expression patterns in the corresponding tissues from control subjects with non-cardiac causes of death. Hba1/2 and Hbb mRNA expression levels were higher in ischemic SCD cases with acute myocardial infarction or ischemic heart disease without recent infarction, and even in cardiac death subjects without apparent pathological signs of heart injuries, than control subjects. By contrast, Pdk4 mRNA was expressed at lower levels in SCD subjects. In conclusion, we found that altered myocardial Hba1/2, Hbb, and Pdk4 mRNA expression patterns can be employed as molecular signatures of fatal cardiac dysfunction to forensically implicate SCD as the primary cause of death.

Forensic molecular pathology: its impacts on routine work, education and training

The major role of forensic pathology is the investigation of human death in relevance to social risk management to determine the cause and process of death, especially in violent and unexpected sudden deaths, which involve social and medicolegal issues of ultimate, personal and public concerns. In addition to the identification of victims and biological materials, forensic molecular pathology contributes to general explanation of the human death process and assessment of individual death on the basis of biological molecular evidence, visualizing dynamic functional changes involved in the dying process that cannot be detected by morphology (pathophysiological or molecular biological vital reactions); the genetic background (genomics), dynamics of gene expression (up-/down-regulation: transcriptomics) and vital phenomena, involving activated biological mediators and degenerative products (proteomics) as well as metabolic deterioration (metabolomics), are detected by DNA analysis, relative quantification of mRNA transcripts using real-time reverse transcription-PCR (RT-PCR), and immunohisto-/immunocytochemistry combined with biochemistry, respectively. Thus, forensic molecular pathology involves the application of omic medical sciences to investigate the genetic basis, and cause and process of death at the biological molecular level in the context of forensic pathology, that is, 'advanced molecular autopsy'. These procedures can be incorporated into routine death investigations as well as guidance, education and training programs in forensic pathology for 'dynamic assessment of the cause and process of death' on the basis of autopsy and laboratory data. Postmortem human data can also contribute to understanding patients' critical conditions in clinical management.

The pathophysiological mechanisms of the onset of death through accidental hypothermia and the presentation of "The little match girl" case

Hypothermia and death caused by hypothermia may be found in a number of fiction works, mainly in novels. In the well-known story “The Little Match Girl” by Hans Christian Andersen, one can notice that the descriptions of the phenomena occurring before the girl’s death are in fact a literary presentation of the pathophysiological mechanisms of the onset of death through accidental hypothermia. This essay presents the medical aspects of the story written by Andersen.

Quantitative analyses of postmortem heat shock protein mRNA profiles in the occipital lobes of human cerebral cortices: implications in cause of death

Quantitative RNA analyses of autopsy materials to diagnose the cause and mechanism of death are challenging tasks in the field of forensic molecular pathology. Alterations in mRNA profiles can be induced by cellular stress responses during supravital reactions as well as by lethal insults at the time of death. Here, we demonstrate that several gene transcripts encoding heat shock proteins (HSPs), a gene family primarily responsible for cellular stress responses, can be differentially expressed in the occipital region of postmortem human cerebral cortices with regard to the cause of death. HSPA2 mRNA levels were higher in subjects who died due to mechanical asphyxiation (ASP), compared with those who died by traumatic injury (TI). By contrast, HSPA7 and A13 gene transcripts were much higher in the TI group than in the ASP and sudden cardiac death (SCD) groups. More importantly, relative abundances between such HSP mRNA species exhibit a stronger correlation to, and thus provide more discriminative information on, the death process than does routine normalization to a housekeeping gene. Therefore, the present study proposes alterations in HSP mRNA composition in the occipital lobe as potential forensic biological markers, which may implicate the cause and process of death.

Stability of endogenous reference genes in postmortem human brains for normalization of quantitative real-time PCR data: comprehensive evaluation using geNorm, NormFinder, and BestKeeper

In forensic molecular pathology, quantitative real-time polymerase chain reaction (RT-qPCR) provides a rapid and sensitive method to investigate functional changes in the death process. Accurate and reliable relative RT-qPCR requires ideal amplification efficiencies of target and reference genes. However, the amplification efficiency, changing during PCR, may be overestimated by the traditional standard curve method. No single gene meets the criteria of an ideal endogenous reference. Therefore, it is necessary to select suitable reference genes for specific requirements. The present study evaluated 32 potential reference genes in the human brain of 15 forensic autopsy cases using three different statistical algorithms, geNorm, NormFinder, and BestKeeper. On RT-qPCR data analyses using a completely objective and noise-resistant algorithm (Real-time PCR Miner), 24 genes met standard efficiency criteria. Validation of their stability and suitability as reference genes using geNorm suggested IPO8 and POLR2A as the most stable ones, and NormFinder indicated that IPO8 and POP4 had the highest expression stabilities, while BestKeeper highlighted ABL1 and ELF1 as reference genes with the least overall variation. Combining these three algorithms suggested the genes IPO8, POLR2A, and PES1 as stable endogenous references in RT-qPCR analysis of human brain samples, with YWHAZ, PPIA, HPRT1, and TBP being the least stable ones. These findings are inconsistent with those of previous studies. Moreover, the relative stability of target and reference genes remains unknown. These observations suggest that suitable reference genes should be selected on the basis of specific requirements, experiment conditions, and the characteristics of target genes in practical applications.