Occupational exposure, carcinogenic and non-carcinogenic risk assessment of formaldehyde in the pathology labs of hospitals in Iran.

Formaldehyde, a known carcinogenic compound, is commonly used in various medical settings. The objective of this study was to assess the carcinogenic and non-carcinogenic risks associated with occupational exposure to formaldehyde. This study was conducted in the pathology labs of four hospitals in Tehran. Cancer and non-cancer risks were evaluated using the quantitative risk assessment method proposed by the United States environmental protection agency (USEPA), along with its provided database known as the integrated risk information system (IRIS). Respiratory symptoms were assessed using the American thoracic society (ATS) questionnaire. The results indicated that 91.23% of exposure levels in occupational groups exceed the NIOSH standard of 0.016 ppm. Regarding carcinogenic risk, 41.03% of all the studied subjects were in the definite carcinogenic risk range (LCR > 10-4), 23.08% were in the possible carcinogenic risk range (10-5 < LCR < 10-4), and 35.90% were in the negligible risk range (LCR < 10-6). The highest index of occupational carcinogenesis was observed in the group of lab technicians with a risk number of 3.7 × 10-4, followed by pathologists with a risk number of 1.7 × 10-4. Furthermore, 23.08% of the studied subjects were within the permitted health risk range (HQ < 1.0), while 76.92% were within the unhealthy risk range (HQ > 1.0). Overall, the findings revealed significantly higher carcinogenic and non-carcinogenic risks among lab technicians and pathologists. Therefore, it is imperative to implement control measures across various hospital departments to mitigate occupational formaldehyde exposure levels proactively. These findings can be valuable for policymakers in the health sector, aiding in the elimination or reduction of airborne formaldehyde exposure in work environments.

Formaldehyde Exposure of Aquaculture Workers in Korea.

OBJECTIVES: Korea's aquaculture sector primarily cultivates aquatic life, with fish seed production as a focus. Formalin, a parasiticide, consists of 37% formaldehyde mixed with yellow No. 4 dye. Formaldehyde vaporization poses cancer risks, classified as a carcinogen. Korea regulates formaldehyde as a hazardous substance, requiring workplace environment measurements. Few aquaculture farms have conducted these checks in recent years. In this study, we investigated actual formaldehyde exposure levels among Korean aquaculture workers, highlighting a critical safety concern. METHODS: A field survey was conducted to measure formaldehyde exposure at 10 aquaculture farms in areas where Korean aquaculture is concentrated. Short-term and long-term personal samples, local samples, and direct-reading measurements were conducted. Formaldehyde exposure levels were detected in short-term personal samples from six farms and in long-term personal samples from two farms, and formaldehyde was detected in all local samples. In direct-reading measurements, a high concentration of formaldehyde was sustained for short periods. RESULTS: Long-term (8-hour) personal samples were mostly non-detectable, except for farms A and D, which had levels of 0.0009 ppm and 0.0017 ppm, respectively. Short-term (15-minute) samples were non-detectable in four farms, with an average of 0.0158 (±0.0130) ppm in the remaining six farms. Local samples from all farms had an average of 0.0384 (±0.0957) ppm of formaldehyde. For farms A and D, where long-term sampling detected formaldehyde, real-time measurements showed a sustained high concentration in farm A for about 48 minutes before decreasing. Farm D had no detectable formaldehyde throughout the monitoring period. CONCLUSION: According to the formaldehyde exposure level assessment, short term exposure to formaldehyde during and immediately after application of formalin nearly exceeded the ACGIH TLV STEL in one farm. However, concentration of long term samples appeared at 10% of ACGIH TLV TWA. Additional study is recommended to determine whether exposure to formaldehyde poses a health risk for aquaculture workers during application of formalin.

The impact of formaldehyde exposure on lung inflammatory disorders: Insights into asthma, bronchitis, and pulmonary fibrosis.

Lung inflammatory disorders are a major global health burden, impacting millions of people and raising rates of morbidity and death across many demographic groups. An industrial chemical and common environmental contaminant, formaldehyde (FA) presents serious health concerns to the respiratory system, including the onset and aggravation of lung inflammatory disorders. Epidemiological studies have shown significant associations between FA exposure levels and the incidence and severity of several respiratory diseases. FA causes inflammation in the respiratory tract via immunological activation, oxidative stress, and airway remodelling, aggravating pre-existing pulmonary inflammation and compromising lung function. Additionally, FA functions as a respiratory sensitizer, causing allergic responses and hypersensitivity pneumonitis in sensitive people. Understanding the complicated processes behind formaldehyde-induced lung inflammation is critical for directing targeted strategies aimed at minimizing environmental exposures and alleviating the burden of formaldehyde-related lung illnesses on global respiratory health. This abstract explores the intricate relationship between FA exposure and lung inflammatory diseases, including asthma, bronchitis, allergic inflammation, lung injury and pulmonary fibrosis.

Ketogenic Diet Alleviates Mechanical Allodynia in the Models of Inflammatory and Neuropathic Pain in Male Mice.

Inflammation is involved in the induction of chronic inflammatory and neuropathic pain. Moreover, the ketogenic diet, a high-fat, low-carbohydrate, and adequate protein diet, has an anti-inflammatory effect. Thus, we hypothesized that a ketogenic diet has a therapeutic effect on both types of chronic pain. In the present study, we investigated the effect of a ketogenic diet on mechanical allodynia, a chronic pain symptom, in formalin-induced chronic inflammatory pain and nerve injury-induced neuropathic pain models using adult male mice. Formalin injection into the hind paw induced mechanical allodynia in both the injected and intact hind paws, and the ketogenic diet alleviated mechanical allodynia in both hind paws. In addition, the ketogenic diet prevented formalin-induced edema. Furthermore, the diet alleviated mechanical allodynia induced by peripheral nerve injury. Thus, these findings indicate that a ketogenic diet has a therapeutic effect on chronic pain induced by inflammation and nerve injury.

Blocking Pannexin 1 Channels Alleviates Peripheral Inflammatory Pain but not Paclitaxel-Induced Neuropathy.

BACKGROUND: Pannexin1 (Panx1) is a membrane channel expressed in different cells of the nervous system and is involved in several pathological conditions, including pain and inflammation. At the central nervous system, the role of Panx1 is already well-established. However, in the periphery, there is a lack of information regarding the participation of Panx1 in neuronal sensitization. The dorsal root ganglion (DRG) is a critical structure for pain processing and modulation. For this reason, understanding the molecular mechanism in the DRG associated with neuronal hypersensitivity has become highly relevant to discovering new possibilities for pain treatment. Here, we aimed to investigate the role of Panx1 in acute nociception and peripheral inflammatory and neuropathic pain by using two different approaches. METHODS: Rats were treated with a selective Panx1 blocker peptide (10Panx) into L5-DRG, followed by ipsilateral intraplantar injection of carrageenan, formalin, or capsaicin. DRG neuronal cells were pre-treated with 10Panx and stimulated by capsaicin to evaluate calcium influx. Panx1 knockout mice (Panx1-KO) received carrageenan or capsaicin into the paw and paclitaxel intraperitoneally. The von Frey test was performed to measure the mechanical threshold of rats' and mice's paws before and after each treatment. RESULTS: Pharmacological blockade of Panx1 in the DRG of rats resulted in a dose-dependent decrease of mechanical allodynia triggered by carrageenan, and nociception decreased in the second phase of formalin. Nociceptive behavior response induced by capsaicin was significantly lower in rats treated with Panx1 blockade into DRG. Neuronal cells with Panx1 blockage showed lower intracellular calcium response than untreated cells after capsaicin administration. Accordingly, Panx1-KO mice showed a robust reduction in mechanical allodynia after carrageenan and a lower nociceptive response to capsaicin. A single dose of paclitaxel promoted acute mechanical pain in wildtype (WT) but not in Panx1-KO mice. Four doses of chemotherapy promoted chronic mechanical allodynia in both genotypes, although Panx1-KO mice had significant ablation in the first eight days. CONCLUSION: Our findings suggest that Panx1 is critical for developing peripheral inflammatory pain and acute nociception involving transient receptor potential vanilloid subtype 1 (TRPV1) but is not essential for neuropathic pain chronicity.

Formaldehyde Exposure Racial Disparities in Southeast Texas.

Formaldehyde (HCHO) exposures during a full year were calculated for different race/ethnicity groups living in Southeast Texas using a chemical transport model tagged to track nine emission categories. Petroleum and industrial emissions were the largest anthropogenic sources of HCHO exposure in Southeast Texas, accounting for 44% of the total HCHO population exposure. Approximately 50% of the HCHO exposures associated with petroleum and industrial sources were directly emitted (primary), while the other 50% formed in the atmosphere (secondary) from precursor emissions of reactive compounds such as ethylene and propylene. Biogenic emissions also formed secondary HCHO that accounted for 11% of the total population-weighted exposure across the study domain. Off-road equipment contributed 3.7% to total population-weighted exposure in Houston, while natural gas combustion contributed 5% in Beaumont. Mobile sources accounted for 3.7% of the total HCHO population exposure, with less than 10% secondary contribution. Exposure disparity patterns changed with the location. Hispanic and Latino residents were exposed to HCHO concentrations +1.75% above average in Houston due to petroleum and industrial sources and natural gas sources. Black and African American residents in Beaumont were exposed to HCHO concentrations +7% above average due to petroleum and industrial sources, off-road equipment, and food cooking. Asian residents in Beaumont were exposed to HCHO concentrations that were +2.5% above average due to HCHO associated with petroleum and industrial sources, off-road vehicles, and food cooking. White residents were exposed to below average HCHO concentrations in all domains because their homes were located further from primary HCHO emission sources. Given the unique features of the exposure disparities in each region, tailored solutions should be developed by local stakeholders. Potential options to consider in the development of those solutions include modifying processes to reduce emissions, installing control equipment to capture emissions, or increasing the distance between industrial sources and residential neighborhoods.

An umbrella review of the evidence associating occupational carcinogens and cancer risk at 19 anatomical sites.

Occupational exposure to carcinogens of increasing cancer risk have been extensively suggested. A robust assessment of these evidence is needed to guide public policy and health care. We aimed to classify the strength of evidence for associations of 13 occupational carcinogens (OCs) and risk of cancers. We searched PubMed and Web of Science up to November 2022 to identify potentially relevant studies. We graded the evidence into convincing, highly suggestive, suggestive, weak, or not significant according to a standardized classification based on: random-effects p value, number of cancer cases, 95% confidence interval of largest study, heterogeneity between studies, 95% prediction interval, small study effect, excess significance bias and sensitivity analyses with credibility ceilings. The quality of meta-analysis was evaluated by AMSTAR 2. Forty-eight articles yielded 79 meta-analyses were included in current umbrella review. Evidence of associations were convincing (class I) or highly suggeastive (class II) for asbestos exposure and increasing risk of lung cancer among smokers (RR = 8.79, 95%CI: 5.81-13.25 for cohort studies and OR = 8.68, 95%CI: 5.68-13.24 for case-control studies), asbestos exposure and increasing risk of mesothelioma (RR = 4.61, 95%CI: 2.57-8.26), and formaldehyde exposure and increasing risk of sinonasal cancer (RR = 1.68, 95%CI: 1.38-2.05). Fifteen associations were supported by suggestive evidence (class III). In summary, the current umbrella review found strong associations between: asbestos exposure and increasing risk of lung cancer among smokers; asbestos exposure and increasing risk of mesothelioma; and formaldehyde exposure and higher risk of sinonasal cancer. Other associations might be genuine, but substantial uncertainty remains.

Sociodemographic inequities in the burden of carcinogenic industrial air emissions in the United States.

BACKGROUND: Industrial facilities are not located uniformly across communities in the United States, but how the burden of exposure to carcinogenic air emissions may vary across population characteristics is unclear. We evaluated differences in carcinogenic industrial pollution among major sociodemographic groups in the United States and Puerto Rico. METHODS: We evaluated cross-sectional associations of population characteristics including race and ethnicity, educational attainment, and poverty at the census tract level with point-source industrial emissions of 21 known human carcinogens using regulatory data from the US Environmental Protection Agency. Odds ratios and 95% confidence intervals comparing the highest emissions (tertile or quintile) to the referent group (zero emissions [ie, nonexposed]) for all sociodemographic characteristics were estimated using multinomial, population density-adjusted logistic regression models. RESULTS: In 2018, approximately 7.4 million people lived in census tracts with nearly 12 million pounds of carcinogenic air releases. The odds of tracts having the greatest burden of benzene, 1,3-butadiene, ethylene oxide, formaldehyde, trichloroethylene, and nickel emissions compared with nonexposed were 10%-20% higher for African American populations, whereas White populations were up to 18% less likely to live in tracts with the highest emissions. Among Hispanic and Latino populations, odds were 16%-21% higher for benzene, 1,3-butadiene, and ethylene oxide. Populations experiencing poverty or with less than high school education were associated with up to 51% higher burden, irrespective of race and ethnicity. CONCLUSIONS: Carcinogenic industrial emissions disproportionately impact African American and Hispanic and Latino populations and people with limited education or experiencing poverty thus representing a source of pollution that may contribute to observed cancer disparities.

Essential Oils from the Genus Piper Promote Antinociception by Modulating TRP Channels and Anti-Inflammatory Effects in Adult Zebrafish.

The Piper genus, known for its pharmacological potential, comprises 2,263 species primarily found in tropical regions. Despite recent advancements in pain therapies, the demand for more effective and well-tolerated analgesics and anti-inflammatories, particularly for chronic pain, remains. This study assessed the effects of essential oils from Piper caldense, Piper mosenii, and Piper mikanianum on nociceptive behavior induced by formalin and capsaicin, as well as their anti-inflammatory impact induced by carrageenan, using adult zebrafish models. Results indicated non-toxic essential oils with antinociceptive properties in both neurogenic and inflammatory phases of formalin-induced nociception through interaction with the TRPA1 receptor. Additionally, P. mosenii essential oil also blocked the nociceptive effect of capsaicin, a TRPV1 receptor agonist. Furthermore, essential oils from P. caldense and P. mikanianum exhibited significant anti-inflammatory effects by reducing carrageenan-induced abdominal edema. These findings highlight the pharmacological potential of Piper's essential oils as antinociceptive and anti-inflammatory agents.

Comparison of side effects and patient perceptions towards Rapid Rhino and Merocel packs in epistaxis.

OBJECTIVE: Non-dissolvable nasal packs (Rapid Rhino and Merocel) are widely used in secondary healthcare centres for the control of epistaxis, with some side effects. METHODS: A prospective, observational cohort study was conducted of adults who required Rapid Rhino or Merocel packing for acute epistaxis management in a large healthcare centre between March 2020 and 2021. A validated modified version of the 22-item Sino-Nasal Outcome Test was used. RESULTS: A total of 80 adults requiring non-dissolvable packs were recruited. Seventy per cent of patients had Rapid Rhino packs inserted. Embarrassment was greater in patients who used Rapid Rhino than Merocel. Merocel packs had a significantly higher mean pain score on removal compared to Rapid Rhino. There was no correlation between rebleed rate and type of nasal pack used. CONCLUSION: Non-dissolvable Rapid Rhino and Merocel nasal packs have similar efficacy in controlling epistaxis. Rapid Rhino packs are more embarrassing for patients in comparison to Merocel packs, but are less painful to remove.

Effects of the orexin receptor 2 agonist danavorexton on emergence from general anaesthesia and opioid-induced sedation, respiratory depression, and analgesia in rats and monkeys.

BACKGROUND: Delayed emergence from general anaesthesia, opioid-induced sedation, and opioid-induced respiratory depression is associated with perioperative complications. We characterised the preclinical effects of the orexin receptor 2 (OX2R)-selective agonist danavorexton (TAK-925) on emergence from anaesthesia and reversal of fentanyl-induced sedation, respiratory depression, and analgesia. METHODS: Emergence from isoflurane- or propofol-induced anaesthesia and fentanyl-induced sedation were investigated by righting reflex, rotarod, and electroencephalography in rats or monkeys. Fentanyl-induced respiratory depression was assessed by arterial blood gas analysis and whole-body plethysmography in rats and monkeys. Analgesia was evaluated using formalin- and skin incision-induced pain models in rats. RESULTS: Danavorexton shortened emergence from isoflurane- or propofol-induced anaesthesia and from fentanyl-induced sedation at 1 (P=0.005), 3 (P=0.006), and 3 mg kg-1 s.c. (P=0.022), respectively, by righting reflex in rats. Danavorexton (10 mg kg-1 s.c.) accelerated recovery from isoflurane-, propofol- and fentanyl-induced motor impairment in separate rotarod tests in rats (P=0.008, P=0.007, P=0.017, respectively), and reversed anaesthesia and fentanyl-induced delta-power increases. Danavorexton shortened emergence (return of righting reflex) from isoflurane- or propofol-induced anaesthesia at 1 (P=0.002) and 3 mg kg-1 (P=0.004), respectively, in cynomolgus monkeys. Danavorexton (10 mg kg-1 s.c.) reversed fentanyl-induced increase in Pco2 (P=0.006), and decrease in Po2 (P=0.015) and pH (P<0.001) in rats, and at 3 mg kg-1 s.c. reversed fentanyl-induced increase in Pco2 (P=0.007), and decrease in Po2 (P=0.013) and SO2 (P=0.036) in monkeys. Danavorexton increased minute volume and tidal volume in fentanyl-treated animals. Danavorexton at ≤10 mg kg-1 s.c. did not compromise fentanyl analgesia in rat formalin- and skin incision-induced pain models. CONCLUSIONS: Danavorexton promoted recovery from anaesthesia and fentanyl-induced sedation, and antagonised fentanyl-induced respiratory depression without compromising fentanyl analgesia.

Non-invasive evaluation of vascular permeability in formalin-induced orofacial pain model using infrared thermography.

Enhanced vascular permeability at the site of injury is a prominent feature in acute inflammatory pain models, commonly assessed through the Evans Blue test. However, this invasive test requires euthanasia, thereby precluding further investigations on the same animal. Due to these limitations, the integration of non-invasive tools such as IRT has been sought. Here, we aimed to evaluate the use of thermography in a common orofacial pain model that employs formalin as a chemical irritant to induce local orofacial inflammation. Male Hannover rats (290-300 g, N = 43) were used. In the first approach, radiometric images were taken before and after formalin administration, assessing temperature changes and extravasated Evans Blue. The second approach included capturing pre- and post-formalin test radiometric images, followed by cytokine measurements in excised vibrissae tissue. Rats were anesthetized for vibrissae tissue collection, allowing correlations between thermographic patterns, nocifensive behavior duration, and cytokine levels in this area. Our findings revealed a positive correlation between local temperature, measured via thermography, and vascular permeability in the contralateral (r2 = 0.3483) and ipsilateral (r2 = 0.4502) side, measured using spectrophotometry. The obtained data supports the notion that thermography-based temperature assessment can effectively evaluate vascular permeability in the orofacial region.

Survival of formalin intoxication in a 13-year-old Thoroughbred gelding.

BACKGROUND: Formalin intoxication via the gastrointestinal route has not been previously reported in the horse. Whereas ingestion of formalin in humans, although rare, is well documented. Majority of human cases are either accidental, suicidal or homicidal and often lead to fatality, with a reported lethal formaldehyde dose equating to 0.12 - 0.16 g/kg bwt. OBJECTIVES: To describe a single case report of the clinical management of an adult horse referred to a veterinary teaching hospital following accidental administration of 10% formalin via nasogastric tube. METHODS: A 13-year-old Thoroughbred gelding originally presented to the referring veterinarian for colic where 1.8 L of 10% formalin was accidentally administered instead of mineral oil via nasogastric intubation, a potentially lethal dose of formaldehyde (0.12 g/kg bwt). Approximately 20-hours following 10% formalin administration the horse was admitted to the referral hospital with moderate tachycardia, occasional ectopic beats, tacky and hyperaemic mucous membranes, delayed capillary refill time, reduced borborygmi, and pronounced digital pulses. Diagnostic investigations included laboratory blood analysis, urinalysis, electrocardiogram, abdominal ultrasound, palpation per rectum and gastroscopy. RESULTS: Patient assessment found evidence of toxicity to the gastrointestinal tract, hypovolaemia and risk for laminitis. Intensive care included fluid and electrolyte therapy, anti-inflammatories and analgesia, continuous digital cryotherapy, gastro-protectants and other methods of gastrointestinal support. The horse was discharged from hospital on day 14 with no long-term complications and the client-veterinarian relationship was preserved. DISCUSSION: In human cases of ingestion, gastrointestinal injury is typically accompanied by severe metabolic acidosis and multiple organ dysfunction syndrome due to toxicity of other body systems that can contribute to non-survival. Formaldehyde toxicity in the present case predominantly affected the gastrointestinal tract, most likely a direct result of the route of administration. Aside from gastrointestinal injury, primary toxicity of other body systems was not confirmed. To prevent this medical error recurring, the referring veterinary clinic revised their labelling and storage of 10% formalin. CONCLUSION: This is the first report of systemic formalin intoxication in the horse. Following a high dose of 10% formalin (0.12 g/kg bwt formaldehyde) enterally, the horse survived having received intensive supportive care based on human guidelines for ingested formalin.

Exogenous histamine and H 2 receptor activation and H 3 receptor inhibition in nucleus accumbens modulate formalin-induced orofacial nociception through opioid receptors.

It has been demonstrated that the nucleus accumbens (NAc) plays an important role in modulation of nociception due to its extensive connections with different regions of the brain. In addition, this nucleus receives histaminergic projections from tuberomammillary nucleus. Considering the role of the central histaminergic system in nociception, the effect of histamine and its H 2 and H 3 receptors agonist and antagonist microinjections into the NAc on orofacial formalin nociception was investigated. In male Wistar rats, using stereotaxic surgery, two guide cannulas were bilaterally implanted into the right and left sides of the NAc. Diluted formalin solution (1.5%, 50 µl) injection into the vibrissa pad led to orofacial nociception. Immediately after injection, face rubbing was observed at 3-min blocks for 45 min. Orofacial formalin nociception was characterized by a biphasic nociceptive response (first phase: 0-3 min and second phase: 15-33 min). Microinjections of histamine (0.5 and 1 µg/site), dimaprit (1 µg/site, H 2 receptor agonist) and thioperamide (2 µg/site, H 3 receptor antagonist) attenuated both phases of formalin orofacial nociception. Prior microinjection of famotidine (2 µg/site) inhibited the antinociceptive effects of dimaprit (1 µg/site). Furthermore, comicroinjection of thioperamide (2 µg/site) and immepip (1 µg/site) prevented thioperamide (2 µg/site)-induced antinociception. Naloxone (2 µg/site) also prevented histamine, dimaprit- and thioperamide-induced antinociception. The results of this study demonstrate that at the level of the NAc, histamine and its H 2 and H 3 receptors are probably involved in the modulation of orofacial nociception with an opioid system-dependent mechanism.

Effect of propranolol on temporomandibular joint pain in repeatedly stressed rats.

Stress substantially increases the risk of developing painful temporomandibular disorders (TMDs) by influencing the release of endogenous catecholamines. Propranolol, an antagonist of ß-adrenergic receptors, has shown potential in alleviating TMD-associated pain, particularly when the level of catecholamines is elevated. The aim of this study was to explore whether intra-articular propranolol administration is effective in diminishing temporomandibular joint (TMJ) pain during repeated stress situations. Additionally, we investigated the effect of repeated stress on the expression of genes encoding ß-adrenoceptors in the trigeminal ganglion. In the present study, rats were exposed to a stress protocol induced by sound, then to the administration of formalin in the TMJ (to elicit a nociceptive response), followed immediately afterward by different doses of propranolol, after which the analgesic response to propranolol was evaluated. We also assessed the levels of beta-1 and beta-2 adrenergic receptor mRNAs (Adrb1 and Adrb2, respectively) using reverse transcription-quantitative PCR (RT-qPCR). Our findings revealed that propranolol administration reduces formalin-induced TMJ nociception more effectively in stressed rats than in non-stressed rats. Furthermore, repeated stress decreases the expression of the Adrb2 gene within the trigeminal ganglion. The findings of this study are noteworthy as they suggest that individuals with a chronic stress history might find potential benefits from ß-blockers in TMD treatment.

A quantitative analysis of surgical smoke-derived particulate matter and formaldehyde exposure during spine surgery: a possible occupational hazard.

OBJECTIVE: Since its introduction, electrocautery has served as a valuable surgical tool, enabling precise tissue cutting and effective hemostasis in spine surgery. While there have been numerous efforts to elucidate the possible hazardous effects of surgical smoke in various surgical fields, there has been very little discussion in the context of spine surgery. The objective of this study was to measure and conduct a quantitative analysis of the particulate matter (PM) of different sizes and of formaldehyde (HCHO) generated by smoke during spine surgeries. METHODS: This study included a consecutive series of patients who underwent 1- or 2-level lumbar spinal fusion surgery between June and November 2021. Particle counts were measured using a particle counter, specifically focusing on six different sizes of PM (0.3, 0.5, 1, 2.5, 5, and 10 µm). Additionally, measurements were taken for HCHO in parts per million (ppm). Monopolar cautery was used in the surgical setting. Systematic measurements were conducted at specific time points during the surgical procedures to assess the levels of PM and HCHO. Furthermore, the efficacy of surgical smoke suction was evaluated by comparing the PM levels with and without adjacent placement of suction. RESULTS: This study involved 35 patients, with measurements of both PM and HCHO taken in 27 cases. The remaining 8 cases had measurements only for PM. In this study, statistically significant quantitative changes in various PM sizes were observed when electrocautery was used during spine surgery (12.3 ± 1.7 vs 1975.7 ± 422.8, 3.4 ± 0.5 vs 250.1 ± 45.7, and 1.9 ± 0.2 vs 78.1 ± 13.3, respectively, for 2.5-, 5-, and 10-µm PM; p < 0.05). The level of HCHO was also significantly higher (0.085 ± 0.006 vs 0.131 ± 0.014 ppm, p < 0.05) with electrocautery use. Utilization of adjacent suction of surgical smoke during electrocautery demonstrated a statistically significant reduction in PM levels. CONCLUSIONS: The findings of this study highlight the potential surgical smoke-related hazards that spine surgeons may be exposed to in the operating room. Implementing simple interventions, such as utilizing nearby suction, can effectively minimize the amount of toxic surgical smoke and mitigate these risks.

Direct inhibition of microglial activation by a µ receptor selective agonist alleviates inflammatory-induced pain hypersensitivity.

Opioids are widely used in the treatment of moderate and severe pain. Nociceptive stimulation has been reported to potentially promote microglial activation and neuroinflammation, which also causes chronic pain sensitization. The aim of this study was to demonstrate whether the novel µ receptor agonist MEL-0614 could inhibit activated microglia directly and the associated signaling pathway. Mice were administered lipopolysaccharide and formalin to induce allodynia. Von Frey test was used to detect the anti-allodynia effect of MEL-0614 before and after LPS and formalin injection. In the spinal cord, the levels of proinflammatory cytokines and microglial activation were determined after MEL-0614 administration. BV2 and primary microglia were cultured to further explore the effect of MEL-0614 on LPS-induced microglial activation and key signaling pathways involved. MEL-0614 partially prevented and reversed allodynia induced by LPS and formalin in vivo, which was not inhibited by the µ receptor antagonist CTAP. Minocycline was effective in reversing the established allodynia. MEL-0614 also downregulated the activation of microglia and related proinflammatory cytokines in the spinal cord. Additionally, in BV2 and primary microglia, MEL-0614 inhibited the LPS-induced upregulation of proinflammatory factors, which was unaffected by CTAP. The NLR family pyrin domain containing 3 (NLRP3) related signaling pathway may be involved in the interaction between MEL-0614 and microglia. The opioid agonist MEL-0614 inhibited the activation of microglia and the subsequent upregulation of proinflammatory factors both in vivo and in vitro. Notably, this effect is partially mediated by the µ receptor.

Mechanisms involved in the antinociceptive and anti-inflammatory effects of xanthotoxin.

Xanthotoxin (XAT) is a natural furanocoumarin clinically used in the treatment of skin diseases such as vitiligo and psoriasis. Recent studies have also investigated its effects on anti-inflammatory, anti-cognitive dysfunction, and anti-amnesia as a guideline for clinic application. However, little is known about its effects on pain relief. Here, we tested the analgesic effects of XAT in serious acute pain and chronic pain models. For acute pain, we used hot-, capsaicin- and formalin-induced paw licking. Nociceptive threshold was measured by mechanical stimuli with von Frey filaments. For chronic pain, we injected complete Freund's adjuvant (CFA) into the mice's plantar surface of the hind paw to induce inflammatory pain. Heat and mechanical hyperalgesia were evaluated by radiant heat and von Frey filament tests, respectively. To investigate the mechanisms underlying the analgesic effect of XAT, we used calcium imaging and western blot to assess transient receptor potential vanilloid 1 (TRPV1) activity and expression in isolated L4-L6 dorsal root ganglion (DRG) neurons. Haematoxylin and eosin (HE) staining, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) were used to examine immune cell recruitment and proinflammatory factor release from skin tissue from paw injection sites. Our results demonstrated that XAT not only reduced acute pain behaviors generated by hot, capsaicin, and formalin but also attenuated CFA-induced heat and mechanical hyperalgesia. The analgesic activity of XAT may be achieved by controlling peripheral inflammation, lowering immune cell infiltration at the site of inflammatory tissue, reducing inflammatory factor production, and therefore inhibiting TRPV1 channel sensitization and expression.