Global practice of sleep medicine: Iran

STUDY OBJECTIVES

This study aimed to conduct a comprehensive review of sleep medicine in Iran, focusing on the country's advancements, challenges, and the global context.

METHODS

We conducted a comprehensive review of sleep medicine in Iran, using various sources to ensure a thorough analysis. The national educational curriculum for sleep medicine and guidelines on sleep clinics issued by Iran's Ministry of Health served as a foundational resource. Additionally, we gathered information from the Iranian Sleep Medicine Society (ISM) website and relevant committee data sources. To enhance our understanding of the current research landscape, we performed a targeted search on PubMed using keywords related to sleep and Iran.

RESULTS

The study presents a dynamic overview of sleep medicine in Iran, highlighting key advancements and challenges. Significant progress was observed in establishing standardized sleep medicine training and accredited sleep clinics. The ISM plays a pivotal role in spearheading these developments, contributing to implementing regional guidelines for sleep tests. However, challenges such as a limited number of trained specialists, a scarcity of certified sleep clinics, and obstacles to accessing sleep disorder treatments were identified.

CONCLUSIONS

We advocate for the implementation of increased research initiatives, nationwide education and screening programs, and proactive measures to strengthen the landscape of sleep and circadian medicine in the country.

An Evaluation of Obstructive Sleep Apnea Patient's Quality of life Following Continuous Positive Airway Pressure and Uvulopalatopharyngoplasty

Aims

Obstructive sleep apnea (OSA) is characterized by episodic sleep state-dependent upper airway collapse. OSA can markedly decrease quality of life (QoL) and productivity. Continuous Positive Airway Pressure (CPAP) has been used as an effective treatment for OSA. Recently, uvulopalatopharyngoplasty (UPPP) treatment has emerged as effective management among patients with OSA, especially non-adherent ones to conventional therapies such as CPAP. Our aim was to determine whether CPAP and UPPP treatment could improve the quality of life in patients with moderate OSA.

Design

Prospective.

Setting

Patients with moderate OSA, confirmed by polysomnography from March 2019 to March 2020, participated. CPAP and UPPP treatments were considered for patients according to their preferences. The Sleep Apnea Quality of Life Index (SAQLI) questionnaire before and after treatment was completed.

Methods

Change in their QoL was compared between the CPAP group and UPPP treatment. In addition, QoL was compared between these groups and patients who did not receive any of these treatment methods.

Results

Seventy-eight patients were included in treatment groups, 40 using CPAP and 38 undergoing UPPP treatment. Furthermore, 10 patients who did not receive treatment were considered the control. Both methods of treatment significantly (p < 0.001) improved QoL, but UPPP treatment was superior (p = 0.042) to CPAP. There was a poor correlation between post-treatment BMI (0.037), Respiratory Disturbance Index (RDI) (0.096), age (0.022), and post-treatment SAQLI score.

Conclusion

Based on these results, CPAP and UPPP treatment can improve QoL. UPPP treatment could be considered an effective arm of OSA management among the study population.

The effects of atomoxetine and trazodone combination on obstructive sleep apnea and sleep microstructure: A double-blind randomized clinical trial study

STUDY OBJECTIVES

we aimed to compare the effects of atomoxetine and trazodone (A-T) in combination with placebo in patients with obstructive sleep apnea (OSA).

METHODS

This randomized, placebo-controlled, double-blind, crossover trial study was conducted in adults with OSA referred to a Sleep Clinic. Participants with eligibility criteria were recruited. Patients were studied on two separate nights with one-week intervals, once treated with trazodone (50 mg) and atomoxetine (80 mg) combination and then with a placebo and the following polysomnography tests.

RESULTS

A total of 18 patients with OSA completed the study protocol, 9(50%) were male, the mean age was 47.5 years (SD = 9.8) and the mean Body mass index of participants was 28.4 kg/m2 (SD = 3.4). Compared with the placebo, the A-T combination resulted in significant differences in AHI (28.3(A-T) vs. 42.7 (placebo), p = 0.025), duration of the REM stage (1.3%TST (A-T) vs. 13.1%TST (placebo), p = 0.001), and the number of REM cycles (0.8 (A-T) vs. 4.7 (placebo), p = 0.001), number of apneas (38.3 (A-T) vs. 79.3 (placebo), p = 0.011), number of obstructive apneas (37.2 (A-T) vs. 75.2 (placebo), p = 0.011), oxygen desaturation index (29.5 (A-T) vs. 42.3 (placebo), p = 0.022) and number of respiratory arousals (43.2 (A-T) vs. 68.5 (placebo), p = 0.048). This decrement effect did not change among those with a low-arousal phenotype of OSA.

CONCLUSIONS

The A-T combination significantly improved respiratory events' indices compared with placebo in patients with OSA. This combination is recommended to be assessed in a large trial. It could be an alternative for those who do not adhere to the standard available treatments for OSA.

Polysomnographic Findings Versus Degree of Obstruction During Drug-Induced Sleep Endoscopy and Muller's Maneuver

PURPOSE

To investigate associations between polysomnographic findings and the severity of upper airway obstructions during Muller's Maneuver (MM) and Drug-Induced Sleep Endoscopy (DISE) in patients with obstructive sleep apnea syndrome (OSAS).

METHODS

This was a prospective cohort study. Adult patients newly diagnosed with OSAS in a tertiary sleep center were included consecutively and evaluated by polysomnography and MM. They then underwent DISE in an operating room. The associations between polysomnographic findings and the severity of upper airway obstructions during MM and DISE were assessed. Also, the degree and pattern of obstructions were compared using a modified VOTE questionnaire.

RESULTS

145 patients (mean age 41.5 ± 10.1 years) were enrolled. There were no associations between Respiratory Disturbance Index (RDI), mean and lowest O2 saturation, and body mass index on the one hand, and obstruction degree in MM and DISE (p > 0.05). However, a significant positive correlation was observed between RDI and total VOTE scores in DISE and MM (r = 0.179, p = 0.031 and r = 0.221, p = 0.008 respectively). There were no differences between MM and DISE in diagnosing the degree of obstruction in the velum area (p = 0.687) and the epiglottis (p = 0.50). However, a significant difference was observed between the two techniques in the oropharynx lateral wall (p < 0.001) and tongue base (p = 0.017).

CONCLUSION

Although there was no association between polysomnographic findings and the severity of obstruction in MM and DISE for the separate levels of the upper airway, obstruction severity may be assessed more accurately by total VOTE score, which is representative of RDI severity.

Uvulopalatopharyngoplasty with and without modified thyrohyoid suspension for obstructive sleep apnea treatment: a randomized clinical trial

PURPOSE

This study aims to compare the efficacy of Uvulopalatopharyngoplasty + Tongue Base Radiofrequency (TB-RF) and Uvulopalatopharyngoplasty + modified thyrohyoid suspension techniques + TB-RF which aimed to suspend base of tongue muscles anteriorly toward thyroid cartilage.

METHODS

This randomized controlled trial study was conducted on 48 cases of confirmed OSA between Jan, 2019 and Aug, 2022. We divided patients into two groups. One group underwent Uvulopalatopharyngoplasty + modified thyrohyoid suspension + TB-RF technique, and another one underwent Uvulopalatopharyngoplasty + TB-RF. Then, Apnea-Hypopnea Index (AHI), mean and lowest O2 saturation, Drug-Induced Sleep Endoscopy (DISE), Epworth Sleepiness Scale (ESS), Digit Symbol Substitution Test (DSST), Stanford Subjective Snoring Scale (SSSS), and T90 indexes were evaluated before and after each surgery.

RESULTS

The mean ± SD age was 39.4 ± 11.17 years. Of the 48 patients, 79.1% (n = 33) were male and 20.9% (n = 15) were female. AHI and SSSS in the Uvulopalatopharyngoplasty + modified thyrohyoid suspension group were significantly better than Uvulopalatopharyngoplasty group (P-value; 0.010). Though, there was no significant difference in terms of mean saturation, lowest desaturation, ESS, DSST, and T90 scores. The success rate in the Uvulopalatopharyngoplasty + modified thyrohyoid suspension and Uvulopalatopharyngoplasty groups, according to the Sher criteria: a minimum of 50% reduction with a final AHI less than 20, were 75% (18/24) and 41.7% (10/24), respectively. It was significantly higher in the Uvulopalatopharyngoplasty + modified thyrohyoid suspension group (P-value: 0.021).

CONCLUSION

The addition of modified thyrohyoid suspension technique to Uvulopalatopharyngoplasty have better surgical outcomes and more success rate than Uvulopalatopharyngoplasty in OSA patients.

TRIAL REGISTRATION

IRCT: IRCT20190602043791N2. https://en.irct.ir/trial/53365 .

Sleep Medicine Evaluation in the Annual Patient Management Problem (PMP) Exam for Otolaryngology Residents

The sleep medicine has not been previously included in the patient management problem (PMP) exam for otolaryngology residents at Tehran University of Medical Sciences. The aim of this study, is to evaluate the results of this first implementation. This was a cross-sectional study. The examinees included all 62 residents from the 1st to 4th years of the Tehran University of Medical Sciences otolaryngology department. The resident scores obtained in this exam were evaluated and compared by residency year. The overall participant score was low for this part of the PMP. There was no score difference between years 1 and 3, but there was a significant positive change in year 4 (p = 0.007). This score pattern was not evident in other parts of the exam. Otolaryngology residents have insufficient knowledge toward the sleep medicine. The reasons for such scoring patterns may be due to the structure of sleep medicine training within the department which may lead to undesirable consequences.

Evaluation of effective factors on pain in patients undergoing sleep apnea surgery

Objectives: The aim of this study was to investigate the factors affecting postoperative pain. Methods: This descriptive cross-sectional study was performed on patients referred to the hospital to determine the factors affecting postoperative pain for patients with obstructive sleep apnea (OSA). Patients' information was recorded: age, sex, weight, height, body mass index, duration of surgery, possible complications, and anesthesia. Patients were evaluated for pain according to VAS criteria. The first time a patient requested a drug was recorded in 24 hours after surgery and data was then analyzed. Results: A total of 40 patients were enrolled in the study, including 14 women (35%) and 26 men (65%). The mean age of patients was 41.55 ± 7.43 years. Examination of the relationships between other variables with patients' pain intensity showed a statistically significant difference between patients' pain intensity with other variables such as history of stroke (P = 0.005), history of cardiovascular disease (P = 0.048), history of drug abuse (P = 0.046) and type of analgesia received after surgery (P = 0.032). In multivariate analysis of the studied data, no statistically significant relationship was found between any of the variables with the intensity of patients' postoperative pain. The variances of height, weight, body mass index, duration of surgery and the first time of application of analgesic after surgery did not differ in different groups of pain intensity variables. But a significant difference was found between the two variables of age and pain intensity of patients (P <0.05). Conclusion: The results of this study showed a statistically significant difference in pain intensity with a history of stroke, cardiovascular disease, history of drug abuse and also the type of analgesia received after surgery. The serious complications caused by tolerating acute postoperative pain, especially the long-term effects of experiencing severe pain, necessitates more attention to pain control.

Paternal exposure to arsenic resulted in oxidative stress, autophagy, and mitochondrial impairments in the HPG axis of pubertal male offspring

Despite the knowledge of AS-induced reprotoxicity, the literature concerning arsenic trioxide (As₂O₃)-induced oxidative stress and consequent intracellular events, like autophagy process, in the hypothalamic-pituitary- gonadal (HPG) axis of F1- pubertal male mice is sparse to date. Hence, we made an attempt to study the reproductive toxicities and the underlying mechanisms induced by As₂O₃ in the HPG axis of pubertal F1- male mice in correlation with oxidative stress-induced autophagy. Parental mice were challenged with As₂O₃ (0, 0.2, 2, and 20 ppm) from five weeks before mating, and continued till puberty age for the male pups. It was recorded that higher As₂O₃ doses (2 and 20 ppm) were a potent inducer of oxidative stress and autophagy in the HPG axis. Concomitant with a decrease on mean body weight, total antioxidant capacity, and stereology indices, an increase in the number of MDC-labeled autophagic vacuoles, and MDA/GSH ratio in HPG axis of pubertal F1- male mice which were exposed to higher As₂O₃ doses was observed. Meanwhile, concomitant with a dose-dependent increment in the gene expression of ATG3, ATG5, Beclin, as well as protein expression of P62, ATG12, and Beclin in HPG axis tissues; a dose-dependent decrease in PI3K and mTOR gene expression was recorded in the HPG tissues of pubertal F₁-males. Altogether, our observations suggest that higher doses of As₂O₃ have detrimental effects on the functionality of HPG axis in pubertal male mice offspring by increasing MDA/GSH ratio and autophagic cell death-related genes and proteins, as well as by reducing total antioxidant capacity.

Is immunosuppression, induced by neonatal thymectomy, compatible with poor reproductive performance in adult male rats?

With increasing knowledge that the immune system has a major impact on reproductive ‎health, the potential for cells arising in organs such as the thymus to alleviate oxidative stress ‎has been revealed. This study addresses the impact of neonatal thymectomy on male ‎reproductive function in pubertal and adult animals. Neonatal Sprague Dawley rats were allotted to four treatments consisting of fully thymectomized, partially thymectomized, intact, and sham-operated rats. Half of the rats in each treatment were sacrificed at 40 and the other half at 80 days of age. Testicular volume, ventral prostate and spleen weight, several sperm attributes (concentration, motility, livability, membrane integrity, sperm penetration into mucus, total antioxidant capacity, mitochondrial dehydrogenase activity), plasma superoxide dismutase, glutathione, and testosterone level as well as fertility decreased in thymectomized rats. Adrenal gland weight, sperm malondialdehyde level, indices of oxidative stress, sperm abnormality, testicular and sperm lipid peroxidation, protein carbonylation, and sperm reactive oxygen species generation increased in thymectomized rats. In thymectomized rats, the testes contained high levels of malondialdehyde but low levels of glutathione and ferric-reducing antioxidant power. Epididymal sperm reactive oxygen species, blood lipid peroxidation, and oxidative stress indices ‎‎in blood and spermatozoa were highest in fully thymectomized, intermediate ‎in partially thymectomized, and lowest in both pubertal and mature control rats. Blood levels of superoxide dismutase, lipid peroxidation indices, and ‎testosterone, and mitochondrial adenosine triphosphate and ‎dehydrogenase activities in epididymal spermatozoa were lowest in fully thymectomized, ‎intermediate in partially thymectomized, and highest in both pubertal and mature control rats.‎ The data indicated that increased oxidative stress and mitochondrial dysfunction might play a role in the mechanism of immunosuppression-induced testicular and sperm abnormalities.

Can testosterone level be a good predictor of late-onset hypogonadism?

Androgens are essential for the development and growth of the genitalia. They regulate the erectile physiology by multiple mechanisms. Several studies have examined associations among sex hormones' serum levels, erectile function and sex drive. We sought to identify a protocol for using testosterone in men with erectile dysfunction and late-onset hypogonadism (LOH). During a 16-month period, men with erectile dysfunction who presented to the andrology clinic were selected. They underwent a complete physical examination and filled out the International Index of Erectile Function-5 questionnaire. Serum luteinising hormone (LH) and testosterone levels were evaluated. Patients received a single intramuscular injection of 250 mg testosterone. Thereafter, serum levels of LH and testosterone were measured 3 weeks later. The mean age was 53 years old. After treating patients with testosterone, 45 (94%) showed improvement in LOH symptoms including libido, loss of energy, irritability and quality of life. The mean International Index of Erectile Function was 9 and 13.1, prior to and after treatment respectively. Mean serum testosterone levels before and after treatment were 4.2 and 4.1 ng ml(-1) respectively (P = 0.849). Mean serum LH revealed a significant decrease after the study (P = 0.004) (6.12 and 5.1 ng ml(-1) , before and after the study respectively). Our findings suggested that testosterone replacement therapy improves libido and LOH symptoms in individuals with almost normal or lower limit normal value of serum testosterone levels.

Amodiaquine-induced toxicity in isolated rat hepatocytes and the cytoprotective effects of taurine and/or N-acetyl cysteine

Amodiaquine is an antimalarial drug used in the prophylaxis and treatment of this disease. However, hepatotoxicity as a life-threatening adverse effect is associated with its clinical use. We evaluated amodiaquine-induced toxicity in isolated rat hepatocytes as an in vitro model for studying drug-induced hepatotoxicity. This study attempts to investigate the protective effects of taurine and N-acetyl cysteine against the cytotoxicity induced by amodiaquine. Hepatocytes were prepared by the method of collagenase enzyme perfusion via portal vein. This technique is based on liver perfusion with collagenase after removal of calcium ion (Ca(2+)) with a chelator (ethylene glycol tetraacetic acid (EGTA) 0.5 mM). Cells were treated with different concentrations of amodiaquine, taurine and N-acetyl cysteine. Cell death, protein carbonylation, reactive oxygen species formation, lipid peroxidation, and mitochondrial depolarization were assessed as toxicity markers. Amodiaquine cytotoxic mechanism involved protein carbonylation as well as reactive oxygen species formation and lipid peroxidation. In addition, mitochondria seem to be a target for amodiaquine to induce cellular damage. Administration of taurine (200 μM) and/or N-acetyl cysteine (200 μM) reduced oxidative stress, lipid peroxidation and protein carbonylation caused by amodiaquine. Furthermore, amodiaquine-induced mitochondrial injury was significantly mitigated by taurine and/or N-acetyl cysteine. In glutathione-depleted cells, only N-acetyl cysteine protected hepatocytes against amodiaquine, and taurine showed no protective properties in this situation. Taurine and N-acetyl cysteine protect hepatocytes against amodiaquine probably via their antioxidant properties and counteracting oxidative stress.

Salt pretreatment enhance salt tolerance in Zea mays L. seedlings

Recent molecular studies show that genetic factors of salt tolerance in halophytes exist in glycophytes too, but they are not active. If these plants expose to low level salt stress these factors may become active and cause plants acclimation to higher salt stresses. So because of the importance of these findings in this research the effect of salt pretreatment has been examined in Zea mays seedlings. To do the experiment four day old Zea mays seedlings (Var. single cross 704) pretreated with 50 mM NaCl for the period of 20 h. Then they were transferred to 200 and 300 mM NaCl for 48 h. At the end of treatment roots and shoots of seedlings were harvested separately. The changes of K+ -leakage, the amount of malondialdehyde, proline, soluble sugars and the Hill reaction rate were analyzed. The results indicated that the amount of K+ -leakage and malondialdehyde (MDA) have been increased because of salt-induced lipid peroxidation and membrane unstability. Soluble sugars and proline as osmoregulators has been increased in stress condition and in pretreated plants with NaCl were the highest. The rate of Hill reaction was reduced significantly in stressed plants. Therefore we concluded that salt stress causes serious physiological and biochemical damages in plants and salt pretreatment enhances tolerance mechanisms of plants and help them to tolerate salt stress and grow on salty environments.

Concentration of heavy metals in different tissues of Astacus leptodactylus from Aras dam of Iran

Due to different human activities in the vicinities of Aras dam, various pollutants such as heavy metals are entered into the reservoir and thus polluting the aquatic ecosystem. As a result, this heavy metal is accumulated in the tissues of Astacus leptodoctylus, which is considered as one the abundant species of crayfish that has got important food values and is of economic importance due to its export to other countries. In this research, the bioaccumulation of heavy metals in different tissues of this animal is taken into consideration. The concentration of Fe, Cu, Zn, Mn, Pb, Ni, Co and Cr among the tissues of female and male Astacus leptodactylus has been determined. The highest concentration of Cu and Fe was found in the gills and the highest level of Zn was found in hepatopancreas. Besides, the highest Mn concentration was recognized in exoskeleton. Furthermore, no significant difference was found between the male and female crayfish in the concentration of the heavy metals in their tissues, except for the concentration of some of the metals such as Fe in some of the tissues such as hepatopancreas.

Effects of lead nitrate (PbNO3) on the glucose and cortisol hormone levels in common carp, Cyprinus carpio

The objective of this study was to evaluate the possible effects of PbNO3 exposure on variations of glucose and cortisol levels in Cyprinus carpio. Fish were subjected to two sub-lethal concentrations of PbNO3 for 14 days. Blood samples were isolated from the fish following the exposure, to measure the levels of cortisol and glucose compared to the control group. We found significant increases (p<0.05) in the levels of blood cortisol in two groups of fish after 14 days of exposure to two concentrations of PbNO3 (1.3 and 2.6 mg L (-1)) The results showed significant increases in the glucose levels of both fish groups exposed for 14 days In the later treatment, the rate of increase in group II (exposed to 2.6 mg L(-1) PbNO3) was higher than that of group I (exposed to 1.3 mg L(-1) PbNO3) (P = 0 compare to P = 0.007). Present findings attest that exposing to waterborne lead would affect the levels of both glucose and cortisol in Cyprinus carpio.

Effects of copper sulfate (CuSO4) on the levels of glucose and cortisol in common carp, Cyprinus carpio

The objective of this study was to evaluate the possible effects of CuSO4 exposure on variations of glucose and cortisol levels in Cyprinus carpio. Three replicates of 6 fish were subjected to two sub-lethal concentrations of CuSO4 (0.16 and 0.53 mg L(-1)) for 14 and 21 days. Blood samples were isolated from the fish following the exposure, to measure the levels of cortisol and glucose compared to the control group. The results showed significant increases (p < 0.05) in cortisol levels for both fish groups after 14 days of exposure, whereas, the levels of blood cortisol in both groups did not differ from that of control when the fish subjected to copper sulfate for 21 days. We found significant increases (p < 0.05) in the levels of blood glucose of two groups of fish after 14 days of exposure to two doses of CuSO4, as well as significant decrease in the blood glucose of both groups exposed for 21 days. In the later treatment, the rate of decrease in group II (exposed to 0.53 mg L(-1) CuSO4) was higher than that of group I (exposed to 0.16 mg L(-1) CuSO4) (p = 0.001 compared to p = 0.032). Our findings attest that exposing to waterborne copper would affect the levels of both cortisol and glucose, as indicators of stress response in Cyprinus carpio.

Histopathological changes in the liver and kidney tissues of Wistar albino rat exposed to fenitrothion

The aim of this study was to investigate the dose-related effects of fenitrothion (FNT) on the liver and kidney. The study was conducted on 8-week-old male Wistar rats that were divided into four groups (three experimental groups and one control group) and were treated orally with different doses (25, 50, 100 mg/kg) of FNT for 28 consecutive days. After treatment, the rats were anesthetized with ether and liver and kidney samples were taken for histological studies. The results showed that the histopathological changes in the liver were mainly represented by parenchymatous degeneration of hepatocytes with mild necrosis, leukocytic infiltration in the portal area, severe congestion, and hemorrhage. These changes were dose dependent. Marked tubular dilation, hydropic degeneration in tubular epithelium, moderate congestion, and hemorrhage in the cortical and medulla part of the kidney were recorded. Histopathologic examination of the liver and kidney indicated a significant injury only in rats receiving 100 mg/kg FNT.

Bioaccumulation of lead nitrate in freshwater crayfish (Astacus leptodactylus) tissues under aquaculture conditions

The aim of this research was to evaluate the amount of lead in the tissue of Astacus leptodactylus especially in their muscle which the consumed part of their body. In this study the crayfish was exposed to intermediate concentration of lead nitrate (500 microg L(-1)) for periods up to 3 weeks. In the first, second and third weeks bioaccumulation in various tissues was under investigation. The data of toxicological analysis obtained by the method of atomic absorption revealed that the levels of bioaccumulation of metal are different in various tissues of this crayfish. The accumulation of the lead in gills was the highest and in muscles was lowest degree. The amount of heavy metals in the tissues of crayfish was as follow. Gills>exoskeleton>hepatopancreas (digestive glands)>digestive tract>green gland>testis and ovary>muscles.

Hydrolysis of individual isomers of fluorogenic pyrethroid analogs by mutant carboxylesterases from Lucilia cuprina

We previously showed that wild-type E3 carboxylesterase of Lucilia cuprina has high activity against Type 1 pyrethroids but much less for the bulkier, alpha-cyano containing Type 2 pyrethroids. Both Types have at least two optical centres and, at least for the Type 1 compounds, we found that wild-type E3 strongly prefers the less insecticidal configurations of the acyl group. However, substitutions to smaller residues at two sites in the acyl pocket of the enzyme substantially increased overall activity, particularly for the more insecticidal isomers. Here we extend these analyses to Type 2 pyrethroids by using fluorogenic analogs of all the diastereomers of cypermethrin and fenvalerate. Wild-type E3 hydrolysed some of these appreciably, but, again, not those corresponding to the most insecticidal isomers. Mutations in the leaving group pocket or oxyanion hole were again generally neutral or deleterious. However, the two sets of mutants in the acyl pocket again improved activity for the more insecticidal acyl group arrangements as well as for the more insecticidal configuration of the cyano moiety on the leaving group. The activities of the best mutant enzyme against the analogs of the most insecticidal isomers of cypermethrin and fenvalerate were more than ten and a hundred fold higher, respectively, than those of wild-type. The implications for resistance development are discussed.

Hydrolysis of organophosphorus insecticides by in vitro modified carboxylesterase E3 from Lucilia cuprina

Resistance of the blowfly, Lucilia cuprina, to organophosphorus (OP) insecticides is due to mutations in LcalphaE7, the gene encoding carboxylesterase E3, that enhance the enzyme's ability to hydrolyse insecticides. Two mutations occur naturally, G137D in the oxyanion hole of the esterase, and W251L in the acyl binding pocket. Previous in vitro mutagenesis and expression of these modifications to the cloned gene have confirmed their functional significance. G137D enhances hydrolysis of diethyl and dimethyl phosphates by 55- and 33-fold, respectively. W251L increases dimethyl phosphate hydrolysis similarly, but only 10-fold for the diethyl homolog; unlike G137D however, it also retains ability to hydrolyse carboxylesters in the leaving group of malathion (malathion carboxylesterase, MCE), conferring strong resistance to this compound. In the present work, we substituted these and nearby amino acids by others expected to affect the efficiency of the enzyme. Changing G137 to glutamate or histidine was less effective than aspartate in improving OP hydrolase activity and like G137D, it diminished MCE activity, primarily through increases in Km. Various substitutions of W251 to other smaller residues had a broadly similar effect to W251L on OP hydrolase and MCE activities, but at least two were quantitatively better in kinetic parameters relating to malathion resistance. One, W251G, which occurs naturally in a malathion resistant hymenopterous parasitoid, improved MCE activity more than 20-fold. Mutations at other sites near the bottom of the catalytic cleft generally diminished OP hydrolase and MCE activities but one, F309L, also yielded some improvements in OP hydrolase activities. The results are discussed in relation to likely steric effects on enzyme-substrate interactions and future evolution of this gene.