Male smokers have a decreased success rate for in vitro fertilization and intracytoplasmic sperm injection

Cigarette smoke extract immobilizes human spermatozoa and induces sperm apoptosis

Cigarette smoking by the male partner adversely affects assisted reproductive techniques, suggesting that it may damage sperm chromatin/DNA and consequently embryo development. The effects of graded concentrations of research cigarettes smoke extract (CSE) on motility, mitochondrial membrane potential (MMP), chromatin integrity and apoptosis were evaluated in spermatozoa obtained from 13 healthy, non-smoking men with normal sperm parameters, by flow cytometry. CSE suppressed sperm motility in a concentration- and time-dependent manner and increased the number of spermatozoa with low MMP, the main source of energy for sperm motility. In addition, CSE had a detrimental effect on sperm chromatin condensation and apoptosis. Indeed, it increased the number of spermatozoa with phosphatidylserine externalization, an early apoptotic sign, and fragmented DNA, a late apoptotic sign, in a concentration- and time-dependent manner. These effects of CSE were of similar or even greater magnitude to those obtained following incubation with tumour necrosis factor-alpha, a cytokine known for its negative impact on sperm function, used as positive control. Since transmission of smoking-induced sperm DNA alterations has been found in pre-implantation embryos, and this may predispose offspring to a greater risk of malformations, cancer and genetic diseases, men seeking to father a child are recommended to give up smoking.

Influence of smoking on outcome of COH and IUI in subfertile couples

AIM

To evaluate the influence of smoking on the outcome of COH and IUI in subfertile couples.

PATIENTS AND METHODS

We reviewed the medical files of all consecutive women, age </=35 years, attending our infertility clinics over an eigth-year period. Data on patient age, smoking habits, and variable related to infertility-treatment were collected from the files.

RESULTS

A total of 2,318 cases were evaluated: 1,803 in nonsmoking patients (n = 679) and 515 in smokers (n = 206). The smokers used significantly more gonadotropin ampoules and gained a thinner endometrium on the day of hCG administration than the nonsmokers (p < 0.016 for both). There were no between-groups differences in patient age, duration of gonadotropin stimulation, number of follicle >14 mm in diameter, or E2 levels on the day of hCG administration.

CONCLUSION

Smokers undergoing COH with IUI required a significantly higher gonadotropin dosage than nonsmokers in order to achieved a comparable pregnancy rate.

Effects of cigarette smoking upon clinical outcomes of assisted reproduction: a meta-analysis

BACKGROUND

The aim of this meta-analysis was to investigate whether any difference exists in success rate of clinical outcomes of assisted reproductive technologies (ART) between women who actively smoke cigarettes at the time of treatment and those who do not.

METHODS

An intensive computerized search was conducted on published literature from eight databases, using search terms related to smoking, assisted reproduction and outcome measures. Eligible studies compared outcomes of ART between cigarette smoking patients and a control group of non-smoking patients and reported on live birth rate per cycle, clinical pregnancy rate per cycle, ectopic pregnancy rate per pregnancy or spontaneous miscarriage rate per pregnancy, and 21 studies were included in the meta-analyses. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated for the data, and statistical heterogeneity was tested for using chi(2) and I(2) values. A systematic review examined the effect of smoking upon fertilization rates across 17 studies.

RESULTS

Smoking patients demonstrated significantly lower odds of live birth per cycle (OR 0.54, 95% CI 0.30-0.99), significantly lower odds of clinical pregnancy per cycle (OR 0.56, 95% CI 0.43-0.73), significantly higher odds of spontaneous miscarriage (OR 2.65, 95% CI 1.33-5.30) and significantly higher odds of ectopic pregnancy (OR 15.69, 95% CI 2.87-85.76). A systematic literature review revealed that fertilization rates were not significantly different between smoking and non-smoking groups in most studies.

CONCLUSIONS

This meta-analysis provides compelling evidence for a significant negative effect of cigarette smoking upon clinical outcomes of ART and should be presented to infertility patients who smoke cigarettes in order to optimize success rates.

Cigarette smoking and reproductive function

PURPOSE OF REVIEW

To perform a systematic review of the literature on the relationship between cigarette smoking and reproductive function. Whenever possible, this review is focused on the most recently published studies (mainly the past 2 years). Nevertheless, in many instances older literature was too relevant not to be taken into account.

RECENT FINDINGS

Tobacco compounds exert a deleterious effect on the process of ovarian follicle maturation. This effect is expressed by worse in-vitro fertilization parameters in cycles performed on women with smoking habits. Also, uterine receptiveness is significantly altered by the smoking habit. In men, cigarette smoking reduces sperm production, increases oxidative stress, and DNA damage. Spermatozoa from smokers have reduced fertilizing capacity, and embryos display lower implantation rates. Even in-utero exposition to tobacco constituents leads to reduced sperm count in adult life.

SUMMARY

A strong body of evidence indicates that the negative effect of cigarette smoking on fertility comprises fairly every system involved in the reproductive process. Couples in reproductive age should be strongly discouraged to smoke.

Two-year outcome after recurrent implantation failure: prognostic factors and additional interventions

Objectives

After recurrent implantation failure (RIF), empirical figures on further prospects are essential for counselling but difficult to estimate within single IVF centres due to high drop-out rates. Alternatively, couples referred to a tertiary unit for RIF were evaluated.

Materials and methods

Multi-centre 2-year observational trial of 1,174 eligible couples treated consecutively with adjuvant lymphocyte immunotherapy (LIT) in a university immunological department from 1999 to 2002 after three or more unsuccessful fresh embryo transfers. Acquisition of data was completed in 2005.

Results

With another 1.5 oocyte retrievals, delivery rate per couple depended on age (39.3% at <30 years, 16.9% at >39 years, P < 0.005). Prognosis was favourable when frozen embryo transfers had been conducted before (34.4 vs. 25.8%, P < 0.005). The outcome was slightly better in ICSI couples as compared to conventional IVF (31.0 vs. 24.8%, P < 0.05). Birth rates per fresh embryo transfer from the fourth to eighth retrieval were 17.4–18.3–15.0–12.9–12.9% (decline not significant). Apart from LIT, further additional interventions were given more often to couples who had had frozen embryo transfers before (49 vs. 40%, P < 0.005).

Conclusions

Female age and ovarian response are crucial for further IVF prognosis. Previous frozen embryo transfers indicate better chances. Couples with male factor infertility may benefit from intracytoplasmatic sperm injection (ICSI) because underlying female factors are less prevalent. Cycle rank had comparatively little impact. Additional interventions are preferentially offered to couples who have a favourable prognosis anyway. Their multiple use is common practice in RIF, but its value should be considered limited.

Weibliche und männliche Fertilitätsstörungen und Risiken der assistierten Fertilisation

Ca. 10–15% der Paare im reproduktionsfähigen Alter bleiben ungewollt kinderlos. Der Anteil steigt tendentiell durch den zunehmend „späten Kinderwunsch“. Das durchschnittliche Alter der Erstgebärenden hat sich u.a. aus Gründen der Ausbildungszeit und Berufstätigkeit der Frau zwischen 1970 und 2000 vom 24. auf das 30. Lebensjahr verschoben. Eine gewollte Kinderlosigkeit kommt in ca. 10% der Ehen vor.

Psychiatric aspects of infertility and infertility treatments

Infertility counseling, whether provided by a psychiatrist or another health care professional, involves the treatment and care of patients, not simply when they are undergoing fertility treatment but also with their long-term emotional well-being, and that of their children and the reproductive helpers who may assist them in achieving biologic or reproductive parenthood. They can educate patients about the side effects of infertility treatment medications and the impact of hormone shifts on psychologic well-being. They are also helpful with differential diagnoses among grief, depressions, and stress; in assessing psychologic preparedness; and in determining the acceptability and suitability of gamete donation, a gestational carrier, or surrogacy as a family-building alternative for individuals, couples, and reproductive collaborators.

Gender effects on the incidence of aneuploidy in mammalian germ cells

Aneuploidy occurs in 0.3% of newborns, 4% of stillbirths, and more than 35% of all human spontaneous abortions. Human gametogenesis is uniquely and gender-specific susceptible to errors in chromosome segregation. Overall, between 1% and 4% of sperm and as many as 20% of human oocytes have been estimated by molecular cytogenetic analysis to be aneuploid. Maternal age remains the paramount aetiological factor associated with human aneuploidy. The majority of extra chromosomes in trisomic offspring appears to be of maternal origin resulting from nondisjunction of homologous chromosomes during the first meiotic division. Differences in the recombination patterns between male and female meiosis may partly account for the striking gender- and chromosome-specific differences in the genesis of human aneuploidy, especially in aged oocytes. Nondisjunction of entire chromosomes during meiosis I as well as premature separation of sister chromatids or homologues prior to meiotic anaphase can contribute to aneuploidy. During meiosis, checkpoints at meiotic prophase and the spindle checkpoint at M-phase can induce meiotic arrest and/or cell death in case of disturbances in pairing/recombination or spindle attachment of chromosomes. It has been suggested that gender differences in aneuploidy may result from more permissive checkpoints in females than males. Furthermore, age-related loss of chromosome cohesion in oocytes as a cause of aneuploidy may be female-specific. Comparative data about the susceptibility of human male and female germ cells to aneuploidy-causing chemicals is lacking. Increases of aneuploidy frequency in sperm have been shown after exposure to therapeutic drugs, occupational agents and lifestyle factors. Conversely, data on oocyte aneuploidy caused by exogenous agents is limited because of the small numbers of oocytes available for analysis combined with potential maternal age effects. The vast majority of animal studies on aneuploidy induction in germ cells represent cause and effect data. Specific studies designed to evaluate possible gender differences in induction of germ cell aneuploidy have not been found. However, the comparison of rodent data available from different laboratories suggests that oocytes are more sensitive than male germ cells when exposed to chemicals that effect the meiotic spindle. Only recently, in vitro experiments, analyses of transgenic animals and knockdown of expression of meiotic genes have started to address the molecular mechanisms underlying chromosome missegregation in mammalian germ cells whereby striking differences between genders could be shown. Such information is needed to clarify the extent and the mechanisms of gender effects, including possible differential susceptibility to environmental agents.

The impact of lifestyle factors on reproductive performance in the general population and those undergoing infertility treatment: a review

This evidence-based review focuses on the impact of potentially modifiable, non-communicable lifestyle factors on reproductive performance in the general population and the infertile population undergoing assisted reproductive technology (ART) treatment. The impact of several lifestyle factors including; age, weight, smoking, diet, exercise, psychological stress, caffeine consumption, alcohol consumption and exposure to environmental pollutants are included in the review. The databases of Medline, PubMed and Cinahl were searched to identify relevant publications. There is strong evidence that age, weight and smoking impact on general health and adversely on reproductive performance. However there is a need for further research focusing specifically on the relationship between diet and various levels of exercise on reproductive performance. There are several other factors such as psychological stress, caffeine consumption, alcohol consumption and exposure to environmental pollutants that have been implicated but the evidence is equivocal. It is concluded that lifestyle modification can assist couples to conceive spontaneously or optimize their chances of conception with ART treatment.

Fécondation in vitro et tabac: intérêt de la cotininurie et de l'analyseur de monoxyde de carbone expiré

OBJECTIVE

To study the correlation between expired air carbon (EACO) and urinary cotinine, and to determine the impact of tobacco smoking on in vitro fertilization (IVF) results.

PATIENTS AND METHODS

We studied prospectively 221 patients in our ART center from October 2002 to October 2004: 51 active smokers, 85 passive smokers, and 85 non-smokers. Patients were classified into active, passive smokers, or non-smokers, based on a questionnaire. We measured urinary cotinine and EACO on the embryo transfer day and we recorded the IVF parameters.

RESULTS

Two hundred and twenty-one patients were included. We observed a 17.2% reduction of estradiolemy (P=0.05), a 1.5% reduction of pregnancies (NS), a 7.8% reduction of infants born alive (NS), a 28.5% reduction of twin pregnancies (P=0.06), as well as a 10% increase of miscarriages (NS) in the active smokers in comparison with non-smokers (the same trends were observed between active and passive smokers). EACO and urinary cotinine were well correlated. There was a negative correlation between estradiolemy and urinary cotinine (R=-0.15, P=0.02).

DISCUSSION AND CONCLUSION

Tobacco smoking intensity may be dilatory on IVF results. There is a high correlation between EACO and urinary cotinine. Other larger studies would probably obtain results more statistically significant.

Preconception care and treatment with assisted reproductive technologies

Couples with fertility problems seeking treatment with assisted reproductive technologies (ART) such as in vitro fertilization should receive preconception counseling on all factors that are provided when counseling patients without fertility problems. Additional counseling should address success rates and possible risks from ART therapies. Success rates from ART are improving, with the highest live birth rates averaging about 40% per cycle among women less than 35 years old. A woman's age lowers the chance of achieving a live birth, as do smoking, obesity, and infertility diagnoses such as hydrosalpinx, uterine leiomyoma, or male factor infertility. Singletons conceived with ART may have lower birth weights. Animal studies suggest that genetic imprinting disorders may be induced by certain embryo culture conditions. The major risk from ovarian stimulation is multiple gestation. About one-third of live-birth deliveries from ART have more than one infant, and twins represent 85% of these multiple-birth children. There are more complications in multiple gestation pregnancies, infants are more likely to be born preterm and with other health problems, and families caring for multiples experience more stress. Transferring fewer embryos per cycle reduces the multiple birth rate from ART, but the patient may have to pay for additional cycles of ART because of a lower likelihood of pregnancy.

Elevated follicle-stimulating hormone levels and the chances for azoospermic men to become fathers after retrieval of elongated spermatids from cryopreserved testicular tissue

OBJECTIVE

To assess individual chances for a live-born child in azoospermic men by performance of testicular sperm extraction (TESE) followed by intracytoplasmatic sperm injection (ICSI).

DESIGN

A retrospective cohort study.

SETTING

An academic fertility care center and research unit.

PATIENT(S)

Two hundred three couples who wished to have a child; all men had azoospermia.

INTERVENTION(S)

All men were operated for TESE; 112 men were found to have elongated spermatids (ES), and 209 ICSI cycles were performed in these men using cryopreserved tissue.

MAIN OUTCOME MEASURE(S)

Predictors for the chances to obtain live sperm and for probabilities of fertilization, clinical pregnancies, and live births.

RESULT(S)

Testicular volume, FSH, and inhibin B levels were predictors for the presence of ES. Intracytoplasmic sperm injection resulted in 23 pregnancies, leading to 20 live births. Despite the presence of ES and performance of ICSI in cases of FSH levels >or=20 IU/L, no pregnancy resulted in these men (n = 21). Receiver operating characteristics revealed FSH levels of >or=20 IU/L as cutoff for treatment success. The number of testicular tubuli containing ES served as a predictor for clinical pregnancy as well as for live birth. Cigarette smoking by the male partner exerted a significant negative influence on treatment success.

CONCLUSION(S)

The degree of completely maintained spermatogenesis within the biopsy appears to reflect intrinsic abilities of spermatozoa to induce normal embryo development. Charts based on regression models are presented for counseling patients before TESE; these explain chances of finding ES and probability of successful ICSI. Obtaining offspring is unlikely in cases of azoospermia and of FSH levels of >or=20 IU/L.

The influence of cigarette smoking on human sperm quality and DNA fragmentation

The aim of the present study was to evaluate consequences of cigarette smoking on male gametes. In this prospective study, sperm parameters such as sperm density, motility, viability and normal morphology were measured according to the WHO criteria. In addition to these standard parameters, we analysed the degree of DNA fragmentation in spermatozoa using the TUNEL-assay with flow cytometry detection in 57 non-smokers and 51 smokers seeking for infertility counselling. The smoking intoxication was assessed by questionnaire and measured with the CO-Tester. We show that smokers' spermatozoa have a significantly higher DNA fragmentation than non-smokers (32% versus 25.9%, p<0.01). In contrast there is no significant difference in conventional parameters between smokers and non-smokers. The degree of sperm DNA fragmentation is not significantly correlated with any of the conventional parameters. These findings suggest that cigarette smoking may have deleterious effects on sperm nuclear quality and that sperm DNA fragmentation can therefore be considered as an independent parameter with diagnostic, prognostic, and strategic value in the treatment of infertility.

The effects of L-carnitine on sperm parameters in smoker and non-smoker patients with idiopathic sperm abnormalities

PURPOSE

To determine the effects of L: -carnitine on sperm parameters in patients with idiopathic sperm abnormalities.

METHODS

In an academic reproductive care center, 170 patients including 48 smokers and 122 non-smokers participated in a before-after study. Men were given 1 g of L: -carnitine orally 3 x daily for 3 months. Sperm assessment was done before and after the treatment. Main outcome measures were sperm concentration, motility, and morphology before and after the treatment.

RESULTS

L-Carnitine was effective in improvement of percentile of motile sperms, grade A sperms, and normal-shaped sperms. L-Carnitine significantly improved percentile of motile and grade A sperms in non-smokers. Only the change in the median percentile of normal forms was within the significant range in smokers.

CONCLUSIONS

The results of this study indicate that smoker patients should not be excluded from the treatment with L-carnitine based on smoking alone.

Effect of lifestyle exposures on sperm aneuploidy

Lifestyle exposures including cigarette smoke, alcohol, and caffeine have all been studied in relationship to male reproductive health. Over the years the focus has primarily been on semen quality and/or fertility. More recently, literature evaluating direct adverse effects of lifestyle exposures on sperm chromosomes and chromatin has grown due to concern that induced damage could be transmitted to offspring causing transgenerational health effects. In this paper we present a new analysis that summarizes published studies of smoking effects on sperm chromosome number and demonstrates a statistically significant increase in sperm disomy among smokers compared to nonsmokers (P < 0.001). In addition, new data on the effect of alcohol intake on sperm chromosome number are presented showing a rate ratio of 1.38 (95% CI 1.2, 1.6) for XY frequency in sperm of alcohol drinkers compared to nondrinkers.

Sperm DNA damage correlates with polycyclic aromatic hydrocarbons biomarker in coke-oven workers

OBJECTIVES

The aim was to determine whether occupational exposure to polycyclic aromatic hydrocarbons (PAHs) in men has adverse effect on semen quality.

METHODS

Forty-eight coke-oven workers, including 16 topside-oven (TO) workers and 32 sideoven (SO) workers, were studied. Ambient PAHs exposure, urinary 1-hydroxypyrene (1-OHP) levels, and parameters of semen quality were determined.

RESULTS

TO workers had significantly higher ambient PAHs exposure (3,436.1+/-3,411.0 vs. 1,123.1+/-1,829.3 ng/m3, P < 0.01), urinary 1-OHP levels (207.8+/-176.4 vs. 54.0+/-44.8 microg/g, P < 0.001), frequency of oligospermia (18.8 vs. 0%, P < 0.05), and morphological abnormality in sperm (32.3 vs. 14.6%, P < 0.01) than SO workers. Among cigarette smokers, TO workers had significantly higher rates of DNA denaturation in spermatozoa (alphaT) and percentage of sperm with increased DNA denaturation (COMP alphaT) levels than SO workers (246.2+/-49.5 vs. 198.1+/-30.3 for alphaT; 34.8+/-14.4 vs. 19.3+/-13.9% for COMP alphaT, P < 0.05). There was a positive correlation between urinary 1-OHP and alphaT, COMP alphaT, and abnormal sperm morphology and a tenfold increase in urinary 1-OHP associated with a 2.35-fold increase in alphaT, as well as a 1.07-fold increase in percentage of sperm with abnormal morphology.

CONCLUSIONS

A potential risk of sperm dysfunction should be considered for workers occupationally exposed to high levels of PAHs. Cigarette smoking may aggravate this risk. Urinary 1-OHP can be used as a biomarker predicting sperm dysfunction.

Smoking habits of parents and male: female ratio in spermatozoa and preimplantation embryos

BACKGROUND

Previous observations have addressed a decreased male:female ratio associated with smoking. Our aim was to assess whether this effect is observed at the spermatozoa or at the early embryo development.

METHODS

We retrospectively assessed smoking intake habits of 56 couples included in our preimplantation genetic diagnosis (PGD) program. Three groups were established according to male or female cigarette consumption per day: non-smokers, smokers (1-19 cigarettes per day) and heavy smokers (> or =20 cigarettes per day). Fluorescence in-situ hybridization (FISH) was performed on ejaculated sperm samples to analyse chromosomes X and Y. On day 3, embryos were also analysed. Additionally, sperm samples from four heavy smoking and four non-smoking donors were prospectively analysed before and after capacitation.

RESULTS

FISH on spermatozoa revealed no statistical differences in the Y:X ratio between the three groups. However, in the PGD study, in male heavy smokers, the XY:XX embryo ratio was decreased compared with non-smokers (22:47 versus 80:71; P = 0.0057). The smoking condition of the female partner had no significant effect on embryo XY:XX ratio, but for non-smoking females with a heavy smoking partner, the ratio was decreased (P = 0.0018) compared with non-smoking males. In heavy smoking donors a decreased of Y:X ratio was observed after swim-up with a statistically significant difference of ratios (P = 0.021).

CONCLUSIONS

Smoking habits of males do not have an effect on the percentage of X- and Y-bearing spermatozoa on ejaculated samples. However, male heavy smokers produce an increased incidence of female embryos that could be related to an enrichment of X spermatozoa after swim-up in patients with high tobacco consumption.

Female and male lifestyle habits and IVF: what is known and unknown

There is no greater tribute to the importance and efficacy of IVF than the fact that >1 x 10(6) babies have been born to infertile couples since its clinical introduction in 1978. Despite enormous advances regarding the technical aspects of the IVF procedure, the parents' contribution has virtually been ignored when considering aspects that influence success rates. This systematic review focuses on the effects of female and male lifestyle habits (specifically: smoking, alcohol and caffeine use, and psychological stress) on the reproductive endpoints of IVF (i.e. oocyte aspiration, fertilization, embryo transfer, achievement of a pregnancy, live birth delivery, and perinatal outcomes, e.g. low birthweight, multiple gestations). What is currently known in the field of lifestyle habits and IVF? There is compelling evidence that smoking has a negative influence on IVF outcomes, whereas for stress, the evidence is suggestive but insufficient due to the heterogeneity of studies. The evidence for the effects of alcohol and caffeine on IVF is inadequate, and therefore unknown, due to the scarcity of studies.

Environmental and occupational factors affecting fertility and IVF success

Reproductive function has been shown to be sensitive to changes in the physical, psychosocial and chemical environments. Although reproductive effects of occupational exposure to hazardous chemicals have been well documented in the literature, the potential effects of chemical contaminants at levels representative of contemporary exposures in the general population are much less certain. Evidence for adverse effects of exposure to environmental contaminants is more conclusive among the lower animals than for humans where considerable controversy remains. In addition to potential reproductive hazards of exposure to environmental contaminants, there is also evidence for adverse reproductive effects of the physical and psychosocial environments. In this review we focus on the difficulties involved in linking exposure to putative hazardous substances in environmental and occupational settings to adverse reproductive outcomes, especially success of IVF procedures. We highlight the plausibility of adverse events through animal and cell studies and the application of these results to the interpretation of human data. We consider both the male and female partners since it is essentially their combined contributions of gametes which may be affected by chemicals, which lead to successful outcomes.

Genotoxicity of tobacco smoke and tobacco smoke condensate: a review

This report reviews the literature on the genotoxicity of mainstream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it has been tested, with the base/neutral fractions being the most mutagenic. In rodents, cigarette smoke induces sister chromatid exchanges (SCEs) and micronuclei in bone marrow and lung cells. In humans, newborns of smoking mothers have elevated frequencies of HPRT mutants, translocations, and DNA strand breaks. Sperm of smokers have elevated frequencies of aneuploidy, DNA adducts, strand breaks, and oxidative damage. Smoking also produces mutagenic cervical mucus, micronuclei in cervical epithelial cells, and genotoxic amniotic fluid. These data suggest that tobacco smoke may be a human germ-cell mutagen. Tobacco smoke produces mutagenic urine, and it is a human somatic-cell mutagen, producing HPRT mutations, SCEs, microsatellite instability, and DNA damage in a variety of tissues. Of the 11 organ sites at which smoking causes cancer in humans, smoking-associated genotoxic effects have been found in all eight that have been examined thus far: oral/nasal, esophagus, pharynx/larynx, lung, pancreas, myeoloid organs, bladder/ureter, uterine cervix. Lung tumors of smokers contain a high frequency and unique spectrum of TP53 and KRAS mutations, reflective of the PAH (and possibly other) compounds in the smoke. Further studies are needed to clarify the modulation of the genotoxicity of tobacco smoke by various genetic polymorphisms. These data support a model of tobacco smoke carcinogenesis in which the components of tobacco smoke induce mutations that accumulate in a field of tissue that, through selection, drive the carcinogenic process. Most of the data reviewed here are from studies of human smokers. Thus, their relevance to humans cannot be denied, and their explanatory powers not easily dismissed. Tobacco smoke is now the most extreme example of a systemic human mutagen.

Nicotinic infertility: assessing DNA and plasma membrane integrity of human spermatozoa

Infertility remains a major problem in society, with recent data suggesting its presence in one of four couples. The objective of the present study was to evaluate the impact of nicotine (0.25, 0.5 and 0.75 mm), as a major component of cigarette smoke, in vitro, on sperm membrane [by spermatocrit and lipoperoxidation (LPO) tests], DNA integrity (by Comet assay), and viability of spermatozoa (by eosin staining) from normozoospermic men. Sperm samples were washed and diluted with phosphate-buffered saline. A drop in spermatocrit values and an increase in thiobarbituric acid-reactive substances/LPO rate was observed with the addition of nicotine, predominantly at a concentration of 0.75 mm, indicating a deleterious effect of nicotine on sperm membrane intactness. There was also a strong negative correlation between LPO rate and percentage viable sperm cell (r = -0.990). Data obtained from Comet assay technique revealed that nicotine could induce double-stranded DNA breaks (11% in 0.75 mm concentration) in the sperm nuclei. The value of r between LPO rate and percentage Comets was found to be +0.976. Taken together, nicotine proved to be a potential oxidant agent in the category of environmental factors to the integrity of sperm plasma membrane and DNA.