Effect of formaldehyde inhalation on Hsp70 in seminiferous tubules of rat testes: an immunohistochemical study

Protective effects of benfotiamine on cyfluthrin-induced testicular damage and sperm characteristics during the prepubertal period

Cyfluthrin, a widely used synthetic pyrethroid insecticide, poses potential risks to both human health and the environment due to its extensive application in residential, agricultural, and outdoor settings. Conversely, benfotiamine, a fat-soluble derivative of vitamin B1, offers versatile therapeutic potential. This experimental study aimed to investigate the impact of cyfluthrin exposure during the prepubertal period on sperm characteristics and testicular tissue integrity in male rats, as well as to assess the protective effects of benfotiamine. A total of 32 4-week-old Wistar albino male rats were divided into four groups. Group I received daily oral gavage of 1 ml/kg/day of olive oil (control). Group II was administered cyfluthrin (54 mg/kg/day) dissolved in 1 ml of olive oil. Group III received both cyfluthrin (54 mg/kg/day) and benfotiamine (100 mg/kg/day) in olive oil. Group IV was given benfotiamine (100 mg/kg/day) in olive oil. After 5 weeks of treatment, the rats underwent evaluations for sperm motility, epididymal sperm density, and abnormal sperm rates. Additionally, their testicular tissues were examined histologically and immunohistochemically. This study underscores the potential hazards of cyfluthrin exposure on male reproductive health and highlights the protective role of benfotiamine in mitigating these effects. It emphasizes the importance of careful pesticide usage and dosage considerations to prevent potential public health issues, including infertility, associated with long-term exposure to pesticides like cyfluthrin.

Serum Concentrations of Benzaldehyde, Isopentanaldehyde and Sex Hormones: Evidence from the National Health and Nutrition Examination Survey

Exposure to environmental chemicals could disturb the balance of sex hormones. However, the studies on Benzaldehyde, Isopentanaldehyde exposure and sex hormones are still limited. Based on the data of 1064 participants in the National Health and Nutrition Examination Survey (NHANES), we used the linear regression model and restricted cubic spline (RCS) model to evaluate the associations of Benzaldehyde/Isopentanaldehyde exposure with testosterone (TT), estradiol (E2), sex hormone binding globulin (SHBG), free androgen index (FAI) and the ratio of TT to E2 (TT/E2). A ln-unit increase in Benzaldehyde was associated with lower TT (β = -0.048, P = 0.030) and E2 (β = -0.094, P = 0.046) in all participants. After further adjustment for menopausal status, Benzaldehyde was negatively associated with E2 (β = -0.174, P = 0.045) in females. The interaction between Benzaldehyde and gender was significant (P_inter = 0.031). However, Isopentanaldehyde showed a positive association with SHBG and TT/E2 in all participants (all P < 0.05). The positive associations of Isopentanaldehyde with TT, SHBG and TT/E2 were found in males but not in females. RCS plots illustrated the linear associations of Benzaldehyde with E2 (P_non-linear = 0.05) in females and Isopentanaldehyde with TT (P_non-linear = 0.07) and TT/E2 (P_non-linear = 0.350) in males. The non-linear relationships were identified between Isopentanaldehyde and SHBG in males (P_non-linear = 0.035). Our findings indicated the effects of Benzaldehyde and Isopentanaldehyde exposure on sex hormones, and the effects had the gender specificity. Cohort studies and high-quality in vitro and in vivo experiments are needed to confirm the specific effects and uncover the underlying mechanisms.

Semen Quality Following Long-term Occupational Exposure to Formaldehyde in China

IMPORTANCE

The potential effects of long-term occupational exposure to formaldehyde (FA) on human semen quality is not clear.

OBJECTIVE

To assess whether long-term occupational exposure to FA is associated with semen quality.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study was conducted from June 1 to June 30, 2021, in Xi'an, China. Participants were adults aged 23 to 40 years who had lived in the study area for 24 months or longer. Data analysis was performed from September 1 to October 1, 2021.

EXPOSURES

Long-term occupational exposure to FA was measured using a formaldehyde detector, and the FA exposure index (FEI) was calculated as follows: FEI = final concentration of FA (mg/m3) × work time during a workday (hour) × cumulative workdays (year).

MAIN OUTCOMES AND MEASURES

Semen samples were collected by masturbation after 3 to 7 days of abstinence and were then assessed by the computer-automated semen analysis system, Baso-Papanicolaou staining, and sperm-chromatin structure assay.

RESULTS

A total of 205 men (mean [SD] age, 29.49 [3.64] years), with 124 individuals in the FA exposure group (mean [SD] FEI, 73.72 [54.86]) and 81 age-matched controls, were included in the final analysis. Long-term personal occupational exposure to FA was significantly associated with poor semen quality. Specifically, a 1-unit increase in FEI was associated with a change of -0.99% (95% CI, -1.00% to -0.98%) in total sperm motility, -0.99% (95% CI, -0.99% to -0.97%) in progressive sperm motility, -0.05% (95% CI, -0.08% to -0.02%) in curvilinear velocity, -0.07% (95% CI, -0.10% to -0.04%) in straight line velocity, -0.07% (95% CI, -0.10% to -0.04%) in time-average velocity, -0.98% (95% CI, -0.99% to -0.93%) in normal sperm morphology, -0.24% (95% CI, -0.35% to -0.11%) in seminal neutral glucosidase, -0.61% (95% CI, -0.66% to -0.56%) in seminal plasma zinc, 0.52% (95% CI, 0.15% to 1.02%) in beat cross frequency, and 0.10% (95% CI, 0.06% to 0.14%) in the DNA fragmentation index. These associations remained significant after adjusting for confounding factors. Furthermore, subgroup analysis found that high levels of oxidative stress might promote the associations between FA exposure and semen quality.

CONCLUSIONS AND RELEVANCE

This study found an association between long-term occupational exposure to FA and semen quality. This deterioration was dose and time dependent and might be induced by oxidative stress.

The effect of hydroethanolic extract of Matricaria chamomilla on the reproductive system of male rats exposed to formaldehyde

Formaldehyde is a common agent in our surrounding environment and can adversely affect the male reproductive system. In this study, the effectiveness of Matricaria chamomilla (MC) extract as an antioxidant was investigated in rats treated with formaldehyde. Thirty-two male Wistar rats were randomly divided into six groups: F (10 mg/kg formaldehyde), M200 (200 mg/kg MC extract), M500 (500 mg/kg MC extract), FM200 (10 mg/kg formaldehyde and 200 mg/kg MC extract), FM500 (10 mg/kg formaldehyde and 500 mg/kg MC extract) and control group (0.9% normal saline). Formaldehyde and MC extract were administered daily for 30 consecutive days via intraperitoneal injection. Hormonal status, sperm parameters, testis tissue histology, germinal cells apoptosis and stereological analyses of testis tissue were investigated. Testosterone and LH levels were significantly increased in FM200, FM500, F200 and F500 groups compared to F group (p ≤ 0.05). Sperm count, motility and viability were significantly enhanced in FM200, FM500, F200 and F500 groups compared to F group (p ≤ 0.05). A decrease in the number of apoptotic germ cells in FM200, FM500, M200 and M500 groups (p ≤ 0.05) was evident. In particular, the MC extract in dose 500 mg/kg is seen to reduce the adverse effects of formaldehyde on the reproductive system of male rats.

Overexpressed Hsp70 alleviated formaldehyde-induced apoptosis partly via PI3K/Akt signaling pathway in human bronchial epithelial cells

Formaldehyde (FA) is a ubiquitous environmental pollutant, which can induce apoptosis in lung cell and is related to the pathogenesis of asthma, pneumonia, and chronic obstructive pulmonary disease. Heat shock protein 70 (Hsp70) is an ATP-dependent molecular chaperone and exhibits an anti-apoptosis ability in a variety of cells. Previous studies reported that the expression of Hsp70 was induced when organisms were exposed to FA. Whether Hsp70 plays a role in the FA-induced apoptosis and the involved cell signaling pathway remain largely unknown. In this study, human bronchial epithelial cells with overexpressed Hsp70 and the control were exposed to different concentrations of FA (0, 40, 80, and 160 μmol/L) for 24 hours. Apoptosis and the expression levels of PI3K, Akt, p-Akt, MEK, p-MEK, and GLI2 were detected by Annexin-APC/7AAD double-labeled flow cytometry and western blot. The results showed that overexpression of Hsp70 decreased the apoptosis induced by FA and alleviated the decline of PI3k and p-Akt significantly. Inhibitor (LY 294002, a specific inhibitor of PI3K-Akt) test result indicated that PI3K-Akt signaling pathway was involved in the inhibition of FA-induced apoptosis by Hsp70 overexpression and also active in the maintenance of GLI2 level. However, it also suggested that other signaling pathways activated by overexpressed Hsp70 participated in this process, which was needed to be elucidated in further research.

The effect of aqueous extract of Rosa damascena on formaldehyde-induced toxicity in mice testes

CONTEXT

Rosa damascena L. (Rosaceae) (RD) essential oil and extracts are commonly used as a flavour in herbal medicine which increase libido. Previous studies have shown inhalation of RD flower's oil increases libido and causes protective effects in formaldehyde (FA)-induced testicular damage.

OBJECTIVE

The protective effects of aqueous extract of RD on the male reproductive system of mice were examined following FA-induced damage.

MATERIALS AND METHODS

Forty-eight adult NMRI male mice were randomly assigned to six groups (n = 8): control (normal saline, 10 mg/kg); RD40 (40 mg/kg, p.o.); FA treated (10 mg/kg of 10%, i.p.) and FA + RD treated at 10, 20 and 40 mg/kg (FA + RD10), (FA + RD20) and (FA + RD40), respectively, for 40 days. At the end of treatment regimes, serum testosterone (T) level and the reproductive activity, viz. body/organ weights, testicular structure and sperm characteristics were studied.

RESULTS

Formaldehyde administration significantly decreased serum T level (p < 0.001), testicular weight/volume, tubular diameter and sperm characteristics compared to the control group (p < 0.05). RD (40 mg/kg) administration in FA-treated mice significantly improved serum T level, testicular weight/histological structure, tubular diameter, Leydig cell number and epididymal sperm characteristics in comparison to its lower doses and the control group (p < 0.05).

DISCUSSION AND CONCLUSIONS

We may conclude that RD flower extract can withstand effects of FA in the male reproductive system of mice possibly due to its antioxidative properties.

Formaldehyde Is a Potent Proteotoxic Stressor Causing Rapid Heat Shock Transcription Factor 1 Activation and Lys48-Linked Polyubiquitination of Proteins

Endogenous and exogenous formaldehyde (FA) has been linked to cancer, neurotoxicity, and other pathophysiologic effects. Molecular and cellular mechanisms that underlie FA-induced damage are poorly understood. In this study, we investigated whether proteotoxicity is an important, unrecognized factor in cell injury caused by FA. We found that irrespective of their cell cycle phases, all FA-treated human cells rapidly accumulated large amounts of proteins with proteasome-targeting K48-linked polyubiquitin, which was comparable with levels of polyubiquitination in proteasome-inhibited MG132 controls. Both nuclear and cytoplasmic proteins were damaged and underwent K48-polyubiquitination. There were no significant changes in the nonproteolytic K63-polyubiquitination of soluble and insoluble cellular proteins. FA also rapidly induced nuclear accumulation and Ser326 phosphorylation of the main heat shock-responsive transcription factor HSF1, which was not a result of protein polyubiquitination. Consistent with the activation of the functional heat shock response, FA strongly elevated the expression of HSP70 genes. In contrast to the responsiveness of the cytoplasmic protein damage sensor HSF1, FA did not activate the unfolded protein response in either the endoplasmic reticulum or mitochondria. Inhibition of HSP90 chaperone activity increased the levels of K48-polyubiquitinated proteins and diminished cell viability after FA treatment. Overall, our results indicate that FA is a strong proteotoxic agent, which helps explain its diverse pathologic effects, including injury in nonproliferative tissues.

Tsga10 expression correlates with sperm profiles in the adult formalin-exposed mice

Testis-specific gene antigen10 (Tsga10), as a cytoskeletal protein in the sperm tail, impacts the sperm motility. This study investigates the correlation between sperm profile alterations and Tsga10 gene expression in adult mice exposed to formaldehyde (FA) and then treated with antioxidant effect of manganese (Mn²⁺ ). In this regard, we examined 35 NMRI adult male mice (6-8 weeks age) in 4 groups of control, sham, FA-exposed and FA+Mn²⁺ . The mice in FA+Mn²⁺ group were exposed to FA (10 mg kg^-1 twice a day) for 2 weeks and treated with daily Mn²⁺ administration (5 mg kg^-1 ) in the second week prior to sacrificing the mice for testis dissection. The right testis was dissected in each group and subjected to RNA extraction and cDNA syntheses for gene expression analysis by real-time PCR. The findings revealed that FA decreased sperm parameters and Tsga10 expression (52.6 ± 24.37%). However, the injected powerful manganese antioxidant improved sperm profile through overexpression of Tsga10 (121.6 ± 27.13%) under FA-induced stressful condition which proves the correlation between sperm profile and Tsga10 expression (P ≤ 0.05). This study also shows that Tsga10 expression protects sperm dysfunction in FA+Mn²⁺ group and resulting in better preservation of spermatozoa and improvement of male fertility.

Effects of Common Fig (Ficus carica) Leaf Extracts on Sperm Parameters and Testis of Mice Intoxicated with Formaldehyde

Formaldehyde (FA) is the leading cause of cellular injury and oxidative damage in testis that is one of the main infertility causes. There has been an increasing evidence of herbal remedies use in male infertility treatment. This assay examines the role of Ficus carica (Fc) leaf extracts in sperm parameters and testis of mice intoxicated with FA. Twenty-five adult male mice were randomly divided into control; sham; FA-treated (10 mg/kg twice per day); Fc-treated (200 mg/kg); and FA + Fc-treated groups. Cauda epididymal spermatozoa were analyzed for viability, count, and motility. Testes were weighed and gonadosomatic index (GSI) was calculated. Also, histoarchitecture of seminiferous tubules was assessed in the Haematoxylin and Eosin stained paraffin sections. The findings showed that FA significantly decreased GSI and increased percentage of immotile sperm compared with control group. Disorganized and vacuolated seminiferous epithelium, spermatogenic arrest, and lumen filled with immature germ cells were also observed in the testes. However, Fc leaf extracts improved sperm count, nonprogressive motility of spermatozoa, and GSI in FA-treated testes. Moreover, seminiferous tubule with spermatogenic arrest was rarely seen, indicating that Fc has the positive effects on testis and epididymal sperm parameters exposed with FA.

The effect of proanthocyanidin on formaldehyde-induced toxicity in rat testes

BACKGROUND/AIM

This study investigated the effect of proanthocyanidin (PA) against formaldehyde (FA)-induced lipid peroxidation damage and morphological changes in rat testes.

MATERIALS AND METHODS

Twenty-one Wistar albino rats were randomized into 3 groups: control, FA, and FA + PA groups. Plasma and tissue malondialdehyde (MDA) and total sialic acid (TSA) levels were measured. Testes tissues were observed by light and electron microscopy.

RESULTS

TSA (plasma and tissue) levels decreased and MDA (plasma) significantly increased (P < 0.05) in rats treated with FA compared to the controls. Tissue MDA levels were not significantly different. Several necrotic changes were observed in testes tissues by light and electron microscopy. Disordering in epithelia of seminiferous tubules, vacuolization between germinal epithelium cells, and separated basement membranes were observed by light microscope. Immunopositivity in Leydig cells decreased in the FA group (P < 0.05). In the FA + PA group there were more immune Leydig cells reacting immune-positively than in the FA group (P < 0.05). Ultrastructurally, FA also caused disorganization and loss of mitochondrial cristae, and dilatation in endoplasmic reticulum in testes.

CONCLUSION

The results suggest that PA has a protective effect on FA toxicity in testes.

Investigation of the protective effects of proanthocyanidin and vitamin E against the toxic effect caused by formaldehyde on the liver tissue

We aimed to investigate of protective role of proanthocyanidin (PA) and vitamin E (vit E) against to toxic effect of formaldehyde (FA). Twenty-eight Wistar albino rats were divided into four groups: control group, rats treated with FA intraperitoneal (i.p.) (10 mg/kg), FA + vit E intragastric (i.g.) (30 mg/kg), and FA + PA i.g. (100 mg/kg). We assayed superoxide dismutase (SOD), glutathione peroxidase (Gpx), myeloperoxidase (MPO) activity and levels of malondialdehyde (MDA) and total sialic acid (TSA) in liver. Liver tissue was taken in order to morphological analysis and hepatocytes apoptosis using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay immunostaining. SOD decreased in FA and increased in FA + vit E and FA + PA (p < 0.05). Gpx didn't change in FA and increased in FA + PA (p < 0.05). No significant variation between the groups was found in MPO activity. MDA increased only in FA and decreased in FA + vit E and FA+PA (p < 0.05). TSA didn't alter in FA and FA + vit E but decreased in FA + PA (p < 0.05). Degeneration in hepatocytes and endothelial cells, cytoplasm losses, vacuolization, picnotic nuclei, and mononuclear cell infiltration were identified in FA. Degeneration in chromatin material, membrane damage in mitochondria and losses in mitochondrial cristae in hepatocytes were observed in FA. We found that partially recovery in liver as a result of FA + vit E and FA + PA. We have concluded that long term use should be investigated for complete explanation of PA's protective effects on FA toxicity.

Associations between occupation exposure to Formaldehyde and semen quality, a primary study

Formaldehyde (FA), a ubiquitous environmental pollutant, has long been suspected of having male reproductive toxicity. However, FA male reproductive toxicity was inconclusive due to dearth of human studies. Therefore, we sought to investigate whether occupational exposure to FA affects semen quality. Semen quality including five conventional parameters and seven kinematics parameters were compared between 114 male workers occupationally exposed to FA and 76 referents. FA exposure index (FEI) was measured and calculated. Our results showed that sperm progressive motility, total sperm motility, VCL, VSL and VAP were statistically significant decreased in FA exposure workers compared with the referents. Moreover, FEI was significantly negative associated with sperm progressive motility (β = -0.19, P = 0.01) and total sperm motility (β = -0.23, P = 0.004). In addition, a significant elevated risk of abnormal sperm progressive motility were observed in both low- (OR = 2.58; 95% CI: 1.11-5.97) and high-FA-exposed group (OR = 3.41; 95% CI: 1.45-7.92) respectively. Furthermore, a significant increased risk was also estimated for abnormal total sperm motility in both low- (OR = 3.21; 95% CI: 1.24-8.28) and high-FA-exposed group (OR = 4.84; 95% CI: 1.83-12.81) respectively. In conclusion, our study revealed the adverse effects of FA occupation exposure on semen quality, especially on sperm motion parameters.

Toxic effects of formaldehyde on the urinary system

Formaldehyde is a chemical substance with a pungent odor that is highly soluble in water and occurs naturally in organisms. Formaldehyde, when taken into organisms, is metabolized into formic acid in the liver and erythrocytes and is then excreted, either with the urine and feces or via the respiratory system. Form-aldehyde is widely used in the industrial and medical fields, and employees in these sectors are frequently exposed to it. Anatomists and medical students are affected by formaldehyde gas during dissection lessons. Because full protection from formaldehyde is impossible for employees in industrial plants using this chemical and for workers in laboratory conditions, several measures can be implemented to prevent and/or reduce the toxic effects of formaldehyde. In this review, we aimed to identify the toxic effects of formaldehyde on the urinary system.

Formaldehyde exposure induces autophagy in testicular tissues of adult male rats

Formaldehyde, a ubiquitous environmental pollutant, has long been suspected of causing adverse male reproductive effects. However, the molecular and cellular mechanisms underlying this phenomenon remain elusive. The overall aim of this study is to clarify the role of autophagy in male reproductive injuries induced by formaldehyde exposure, by which we can further understand the molecular mechanism of spermatogenesis and develop new targets for prevention and treatment of male infertility. In this study, electron microscopy, Western blot, and RT-PCR analysis were used to detect autophagy in testicular tissues. Moreover, testicular weights, histopathology, and morphometry were used to evaluate the reproductive injuries of formaldehyde exposure. We found that formaldehyde exposure-induced autophagy in testicular tissues was dose dependent. Increasing autophagosomes in spermatogenetic cells was observed by electron microscopy in formaldehyde exposure group. In addition, RT-PCR and Western blot analysis showed the transcription levels of the LC3-II, as well as the conversion from LC3-I to LC3-II, an indicator of autophagy, significantly increased in testicular tissue of formaldehyde exposure group in a dose dependent manner when compared with those in control group. Furthermore, the alterations of autophage were basically consistent with the changes in testicular weight and morphologic findings. In summary, formaldehyde exposure triggered autophagy, and autophagy may be a scathing factor responsible for male reproductive impairment induced by formaldehyde.

Effects of formaldehyde inhalation on humoral immunity and protective effect of Nigella sativa oil: An experimental study

AIM

This study was carried out to determine the effects of formaldehyde (FA) inhalation on the humoral immunity of rats and the protective effect of Nigella sativa (NS) oil.

MATERIALS AND METHODS

The rats (n = 33) were divided into five groups, with five animals in the control group (FA-free air) and seven in the other four groups. Group FA1 was exposed to FA (5 ppm), group FA + NS1 was treated with NS and exposed to FA (5 ppm), group FA2 was exposed to FA (10 ppm), and group FA + NS2 was treated with NS and exposed to FA (10 ppm). At the end of a 4-week study period, blood samples were collected. Enzyme-linked immunosorbent assay was used to determine the levels of serum total immunoglobulin A (IgA), total immunoglobulin M (IgM), total immunoglobulin G (IgG), and complement 3 (C3).

RESULTS

FA inhalation significantly increased serum IgA, IgM, and C3 levels and decreased serum IgG levels compared with the control group. NS administration decreased serum IgA, IgM, and C3 levels, which were induced by FA inhalation.

CONCLUSION

FA inhalation significantly increased acute antibody responses and C3 levels in a dose-dependent manner compared with the control group. FA inhalation decreased the secondary immune response compared with the control group. Levels of acute antibody responses and complement following exposure to FA inhalation returned to normal following treatment with NS (immunoregulatory effect). However, NS did not affect the secondary immune response.

Effect of selenium on neurotoxicity in adult male mice exposed to formaldehyde

BACKGROUND

Formaldehyde is used in medicine and industry, and it is known to have detrimental effects on various systems including the nervous system, by increasing oxidative stress. However, data are scarce related to substances that can protect against the neurotoxicity induced by formaldehyde. Therefore, this study was designed to assess the protective effects of selenium against the toxic effect of this compound.

METHODS

A total of 48 adult male mice were divided randomly into six groups, i.e., (1) control, (2) treated with formaldehyde, (3) treated with formaldehyde plus 0.1 mg/kg selenium, (4) treated with formaldehyde plus 0.2 mg/kg selenium, (5) treated with formaldehyde plus 0.4 mg/kg selenium, and (6) treated with formaldehyde plus 0.8 mg/kg selenium. At the end of 14 days, the cerebellums were removed for histological evaluation. Morphological changes were examined using Image J software. The data were analyzed using SPSS software version 20.0 and analysis of variance (ANOVA).

RESULTS

Formaldehyde caused a reduction in the numbers and sizes of Purkinje cells and granular cells; in addition, the thickness of the granular layer was thinner than that in the control mice (P < 0.05). Treatment with 0.1 mg/kg selenium resulted in an increase in the number of Purkinje cells as well as the area of the gray matter compared to those of the control mice.

CONCLUSION

Formaldehyde-induced neuronal damage was prevented by the administration of 0.1 mg/kg selenium, hence this treatment shows therapeutic potential for the treatment of neurotoxicity.

Lymphohematopoietic cancers induced by chemicals and other agents and their implications for risk evaluation: An overview

Lymphohematopoietic neoplasia are one of the most common types of cancer induced by therapeutic and environmental agents. Of the more than 100 human carcinogens identified by the International Agency for Research on Cancer, approximately 25% induce leukemias or lymphomas. The objective of this review is to provide an introduction into the origins and mechanisms underlying lymphohematopoietic cancers induced by xenobiotics in humans with an emphasis on acute myeloid leukemia, and discuss the implications of this information for risk assessment. Among the agents causing lymphohematopoietic cancers, a number of patterns were observed. Most physical and chemical leukemia-inducing agents such as the therapeutic alkylating agents, topoisomerase II inhibitors, and ionizing radiation induce mainly acute myeloid leukemia through DNA-damaging mechanisms that result in either gene or chromosomal mutations. In contrast, biological agents and a few immunosuppressive chemicals induce primarily lymphoid neoplasms through mechanisms that involve alterations in immune response. Among the environmental agents examined, benzene was clearly associated with acute myeloid leukemia in humans, with increasing but still limited evidence for an association with lymphoid neoplasms. Ethylene oxide and 1,3-butadiene were linked primarily to lymphoid cancers. Although the association between formaldehyde and leukemia remains controversial, several recent evaluations have indicated a potential link between formaldehyde and acute myeloid leukemia. The four environmental agents examined in detail were all genotoxic, inducing gene mutations, chromosomal alterations, and/or micronuclei in vivo. Although it is clear that rapid progress has been made in recent years in our understanding of leukemogenesis, many questions remain for future research regarding chemically induced leukemias and lymphomas, including the mechanisms by which the environmental agents reviewed here induce these diseases and the risks associated with exposures to such agents.

Amended Safety Assessment of Formaldehyde and Methylene Glycol as Used in Cosmetics

Formaldehyde and methylene glycol may be used safely in cosmetics if established limits are not exceeded and are safe for use in nail hardeners in the present practices of use and concentration, which include instructions to avoid skin contact. In hair-smoothing products, however, in the present practices of use and concentration, formaldehyde and methylene glycol are unsafe. Methylene glycol is continuously converted to formaldehyde, and vice versa, even at equilibrium, which can be easily shifted by heating, drying, and other conditions to increase the amount of formaldehyde. This rapid, reversible formaldehyde/methylene glycol equilibrium is distinguished from the slow, irreversible release of formaldehyde resulting from the so-called formaldehyde releaser preservatives, which are not addressed in this safety assessment (formaldehyde releasers may continue to be safely used in cosmetics at the levels established in their individual Cosmetic Ingredient Review safety assessments).

Recent trend in risk assessment of formaldehyde exposures from indoor air

Studies about formaldehyde (FA) published since the guideline of 0.1 mg/m(3) by the World Health Organization (WHO) in 2010 have been evaluated; critical effects were eye and nasal (portal-of-entry) irritation. Also, it was considered to prevent long-term effects, including all types of cancer. The majority of the recent toxicokinetic studies showed no exposure-dependent FA-DNA adducts outside the portal-of-entry area and FA-DNA adducts at distant sites were due to endogenously generated FA. The no-observed-adverse-effect level for sensory irritation was 0.5 ppm and recently reconfirmed in hypo- and hypersensitive individuals. Investigation of the relationship between FA exposure and asthma or other airway effects in children showed no convincing association. In rats, repeated exposures showed no point mutation in the p53 and K-Ras genes at ≤15 ppm neither increased cell proliferation, histopathological changes and changes in gene expression at 0.7 ppm. Repeated controlled exposures (0.5 ppm with peaks at 1 ppm) did not increase micronucleus formation in human buccal cells or nasal tissue (0.7 ppm) or in vivo genotoxicity in peripheral blood lymphocytes (0.7 ppm), but higher occupational exposures were associated with genotoxicity in buccal cells and cultivated peripheral blood lymphocytes. It is still valid that exposures not inducing nasal squamous cell carcinoma in rats will not induce nasopharyngeal cancer or lymphohematopoietic malignancies in humans. Reproductive and developmental toxicity are not considered relevant in the absence of sensory irritation. In conclusion, the WHO guideline has been strengthened.

Effects of paternal occupation exposure to formaldehyde on reproductive outcomes

OBJECTIVE

To investigate whether paternal occupational exposure to formaldehyde (FA) affects the reproductive outcomes.

METHODS

Data were collected from 302 male workers occupationally exposed to FA and 305 referent controls through interview questionnaires. Formaldehyde exposure level was measured and calculated for every subject. Different reproductive outcomes were compared for two groups by logistic regression analyses.

RESULTS

A significant increased risk of prolonged time to pregnancy (P = 0.034; odds ratio, 2.828; 95% confidence interval, 1.081 to 7.406) and significant elevated risk of spontaneous abortion (P = 0.021; odds ratio, 1.916; 95% confidence interval, 1.103 to 3.329) were observed in wives of male workers occupationally exposed to FA after correction for confounding factors. Moreover, reproductive toxicity due to FA exposure is dose dependent.

CONCLUSIONS

This epidemiological study adds some evidence for the hypothesis that paternal FA occupation exposure has adverse effects on reproductive outcomes.

The impact of long-term exposure to space environment on adult mammalian organisms: a study on mouse thyroid and testis

Hormonal changes in humans during spaceflight have been demonstrated but the underlying mechanisms are still unknown. To clarify this point thyroid and testis/epididymis, both regulated by anterior pituitary gland, have been analyzed on long-term space-exposed male C57BL/10 mice, either wild type or pleiotrophin transgenic, overexpressing osteoblast stimulating factor-1. Glands were submitted to morphological and functional analysis.In thyroids, volumetric ratios between thyrocytes and colloid were measured. cAMP production in 10(-7)M and 10(-8)M thyrotropin-treated samples was studied. Thyrotropin receptor and caveolin-1 were quantitized by immunoblotting and localized by immunofluorescence. In space-exposed animals, both basal and thyrotropin-stimulated cAMP production were always higher. Also, the structure of thyroid follicles appeared more organized, while thyrotropin receptor and caveolin-1 were overexpressed. Unlike the control samples, in the space samples thyrotropin receptor and caveolin-1 were both observed at the intracellular junctions, suggesting their interaction in specific cell membrane microdomains.In testes, immunofluorescent reaction for 3β- steroid dehydrogenase was performed and the relative expressions of hormone receptors and interleukin-1β were quantified by RT-PCR. Epididymal sperm number was counted. In space-exposed animals, the presence of 3β and 17β steroid dehydrogenase was reduced. Also, the expression of androgen and follicle stimulating hormone receptors increased while lutenizing hormone receptor levels were not affected. The interleukin 1 β expression was upregulated. The tubular architecture was altered and the sperm cell number was significantly reduced in spaceflight mouse epididymis (approx. -90% vs. laboratory and ground controls), indicating that the space environment may lead to degenerative changes in seminiferous tubules.Space-induced changes of structure and function of thyroid and testis/epididymis could be responsible for variations of hormone levels in human during space missions. More research, hopefully a reflight of MDS, would be needed to establish whether the space environment acts directly on the peripheral glands or induces changes in the hypotalamus-pituitary-glandular axis.

Reproductive and developmental toxicity of formaldehyde: a systematic review

Formaldehyde, the recently classified carcinogen and ubiquitous environmental contaminant, has long been suspected of causing adverse reproductive and developmental effects, but previous reviews were inconclusive, due in part, to limitations in the design of many of the human population studies. In the current review, we systematically evaluated evidence of an association between formaldehyde exposure and adverse reproductive and developmental effects, in human populations and in vivo animal studies, in the peer-reviewed literature. The mostly retrospective human studies provided evidence of an association of maternal exposure with adverse reproductive and developmental effects. Further assessment of this association by meta-analysis revealed an increased risk of spontaneous abortion (1.76, 95% CI 1.20-2.59, p=0.002) and of all adverse pregnancy outcomes combined (1.54, 95% CI 1.27-1.88, p<0.001), in formaldehyde-exposed women, although differential recall, selection bias, or confounding cannot be ruled out. Evaluation of the animal studies including all routes of exposure, doses and dosing regimens studied, suggested positive associations between formaldehyde exposure and reproductive toxicity, mostly in males. Potential mechanisms underlying formaldehyde-induced reproductive and developmental toxicities, including chromosome and DNA damage (genotoxicity), oxidative stress, altered level and/or function of enzymes, hormones and proteins, apoptosis, toxicogenomic and epigenomic effects (such as DNA methylation), were identified. To clarify these associations, well-designed molecular epidemiologic studies, that include quantitative exposure assessment and diminish confounding factors, should examine both reproductive and developmental outcomes associated with exposure in males and females. Together with mechanistic and animal studies, this will allow us to better understand the systemic effect of formaldehyde exposure.

Assessment of the potential reproductive toxicity of long-term exposure of adult male rats to low-dose formaldehyde

Formaldehyde (FA), a ubiquitous environmental pollutant, is extensively used in hospitals, laboratories and many industrial settings. Previous studies have showed that short-term, high-dose FA exposure is toxic to male reproduction of mammals. In this paper, we evaluated the male reproductive toxicity of long-term, low-dose formaldehyde exposure in rats, and explored the potential mechanisms. A total of 30 Sprague-Dawley male rats were randomly allotted to three groups, rats were exposed to FA at a dose of 0 (control), 0.5, 2.46 mg/m3 respectively by inhalation for consecutive 60 days. The results indicated that the reproductive toxicity of FA is dose-dependent. Testicular, epididymal structure and function in rats of 0.5 mg/m3 FA exposure group showed no obvious difference compared with those in control group. However, sperm quantity and quality, testicular seminiferous tubular diameter, the activities of superoxide dismutase and glutathione peroxidase was significantly decreased whereas the level of malondialdehyde was significantly increased in rats of 2.46 mg/m3 FA exposure group compared with those in control group. Moreover, histopathological results showed atrophy of seminiferous tubules, decreases of spermatogenic cells and the lumina were oligozoospermic in testes of 2.46 mg/m3 FA exposure rats. In conclusion, the level of 0.5 mg/m 3 can be considered as a safe level for FA exposure, but long-term FA exposure at a dose of 2.46 mg/m3 has a harmful effect on male reproduction by inducing oxidative stress in male rats.

Protective effects of melatonin against formaldehyde-induced oxidative damage and apoptosis in rat testes: an immunohistochemical and biochemical study

This study investigated the protective effects of melatonin against formaldehyde-induced oxidative damage and apoptosis in rat testes. A total of 21 male Wistar rats were divided into three groups. Group I was used as a control, Group II was injected every other day with formaldehyde for 1 month, whereas Group III was injected every other day with formaldehyde and melatonin for 1 month. At the end of the experimental period animals were sacrificed and the testes removed and dissected from the surrounding tissues for immunohistochemical evaluation. In addition, the levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) were determined. The levels of SOD and GSH-Px decreased significantly, whereas the level of MDA significantly increased in animals treated with formaldehyde compared with the controls. Apoptosis of spermatogenetic and Leydig cells of testicular tissues was observed. In contrast, rats with melatonin SOD and GSH-Px enzyme activity increased whereas MDA levels decreased with formaldehyde exposure along with apoptosis. In view of the present findings, it is suggested that melatonin treatment may prevent formaldehyde-induced oxidative damage and apoptosis in rat testes.

Effects of formaldehyde inhalation on the junctional proteins of nasal respiratory mucosa of rats

Exposure to formaldehyde, which is an organic compound, disturbs the integrity of nasal mucosa. In this study, we aimed to clarify the protein changes in the junctional complex of nasal mucosa of Wistar rats exposed to formaldehyde inhalation. The study was performed in 20 female Wistar rats. Rats were divided into two groups randomly. Control rats were allowed free access to standard rat chaw and tap water (n:10). Experimental group was exposed to formaldehyde vapor at 15ppm, 6h/day, 5 days/week for 12 weeks (n:10). Histological evaluation of the experimental model was determined by hematoxylin-eosin (HE) and periodic acid Schiff (PAS) stainings of paraffin-embedded nasal mucosa tissues and by electron microscopy. The effects of formaldehyde inhalation on the distribution of occludin, E-cadherin, and gamma-catenin were assessed by immunohistochemistry. The nasal mucosa of the experimental group was correlated with hypertrophy in goblet cell, degeneration in basal lamina, stratification of epithelium, and proliferation. Thickness of basal lamina and also local degenerative regions, vacuole increase in cytoplasmic areas, irregular forms of kinocilium and loss of sharpness in the kinocilium membrane were the findings at the ultrastructural level. The expressions of E-cadherin, occludin, gamma-catenin proteins in intercellular junctional complexes of rat nasal mucosa were also decreased in experimental group compared to control group. The findings of the present study indicated that formaldehyde vapor inhalation in the concentrations and duration of exposure used in the present experiment significantly decreased the density of structural proteins of the junctional complex in the nasoepithelium. It was suggested that, the formaldehyde inhalation could cause complete impairment of intercellular junctional complexes and disturb the tissue integrity in nasal mucosa at higher concentrations.

Should forensic autopsies be a source for medical education? A preliminary study

BACKGROUND

Practical anatomy sessions including dissection of cadavers are essential for anatomy courses. There are many difficulties in obtaining cadavers. In addition, hardened and discolored cadavers that are fixed with formaldehyde look unrealistic and generate apathy among students.

PURPOSE

We considered that forensic autopsies may be used as ancillary and supportive practice in anatomy education.

METHODS

We invited the participation of Year 2 medical students in suitable forensic autopsy cases during the course of one year. Specialists of forensic medicine and anatomy provided theoretical support through talks in their specialized fields during the autopsy. At the end of the semester, feedback questionnaire forms were prepared and the students were asked to evaluate these sessions.

RESULTS

Forty students participated in the evaluation by completing the questionnaire. Students made positive statements about adequacy of the time of the application, consistency of the structures with theoretical and practical issues shown in anatomy lectures, and necessary explanations of the lecturers during and after the application.

CONCLUSION

We think that forensic autopsies are an attractive supplementary educational model, and we have decided to continue the forensic autopsy practices. We believe that further studies on the evaluation of the sessions using a larger student population will lead to more conclusive results.