Lung atypical adenomatous hyperplasia (AAH) is a forerunner of pulmonary adenocarcinoma. The drugs being utilized in the remediation of this type of hyperplasia have some adverse impacts. The present research focused on the potential anti-hyperplasia effect of myrtenol, an herbal terpenoid, on urethane-induced lung AAH in rats. Rats were injected with urethane (1.5 g/kg) thrice at 48 h intervals, and 20 weeks later, the animals were treated with 50 mg/kg myrtenol intraperitoneally once a day for 1 week. The ELISA method was used to measure inflammatory cytokines and oxidative parameters in the lung tissue and bronchoalveolar lavage fluid (BALF). The expression of NFκB and apoptotic/antiapoptotic factors (P53/Bcl-2) was evaluated by western blot and immunohistochemistry, respectively. H&E staining was performed for histopathological investigation. Histopathology confirmed the anti-hyperplasia effect of myrtenol, which was evidenced by the reduction of bronchoalveolar wall thickness and inflammation score. It also decreased hyperplasia progression by reducing Bcl-2, IL-10, p53, and Ki67. Compared with the urethane group, myrtenol normalized the activity of the oxidative stress markers malondialdehyde (MDA), total antioxidant capacity (TAC), glutathione peroxidase (GPX), and superoxide dismutase (SOD). Moreover, it showed an anti-inflammatory effect by decreasing lung and BALF IL-1β levels and NFκB expression. Myrtenol may have a promising effect on lung cancer treatment by counteracting lung hyperplasia via modulation of inflammation, oxidative stress, and apoptosis.

Asthma is an inflammatory disorder with significant health problems. It generally affects the lungs but can also impact brain performance via several mechanisms. Some investigations have proposed that asthma impairs cognition. This study assessed the impacts of myrtenol as a monoterpene on cognitive disorders following asthma at behavioral, molecular, and synaptic levels. Asthma was induced by injection and inhalation of ovalbumin (OVA). Male Wistar rats were allocated to five groups: control, asthma, asthma/vehicle, asthma/myrtenol, and asthma/budesonide. Myrtenol (8 mg/kg) or budesonide (160 μg/kg) was administered through inhalation once a day for 1 week, and at the end of the inhalation period, behavioral tests (MWM and Open Field), field potential recording, hippocampal brain-derived neurotrophic factor (BDNF), IL1β (ELISA), and NFκB measurement (Western blot) were performed to evaluate cognitive performance. Moreover, H&E (hematoxylin and eosin) staining was used for hippocampus histological evaluation. Myrtenol improved spatial learning, memory, LTP (long-term potentiation) impairments, and anxiety-like behaviors following asthma. Myrtenol inhalation increased the BDNF level and decreased the IL1β level and NFκB expression in the hippocampus of the asthmatic rats. The neuronal damage in the hippocampus following allergic asthma was alleviated via myrtenol administration. Myrtenol, as an herbal extract, protects the hippocampus from asthma consequences. Our observations revealed that myrtenol can improve spatial learning, memory, synaptic plasticity impairments, and anxiety-like behaviors following asthma. We believe that these ameliorating effects of myrtenol can be attributed to inflammation suppression and increased BDNF in the hippocampus.

Ischemia-reperfusion injury (IRI) is directly related to forming reactive oxygen species, endothelial cell injury, increased vascular permeability, and the activation of neutrophils and cytokines. Niosomes are nanocarriers and an essential part of drug delivery systems. We aimed to investigate the effects of myrtenol\'s inhaled and intraperitoneal niosomal form, compared to its simple form, on lung ischemia reperfusion injury (LIRI).
Wistar rats were divided into ten groups. Simple and niosomal forms of myrtenol were inhaled or intraperitoneally injected daily for one week prior to LIRI. We evaluated oxidative stress, apoptotic, and inflammatory indices, nitric oxide, inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS) and histopathological indices.
Pretreatment with simple and niosomal forms of myrtenol significantly inhibited the indices of pulmonary edema, pro-inflammatory cytokines and proteins, oxidant agents, nitric oxide, iNOS, apoptotic proteins, congestion of capillaries, neutrophil infiltration, and bleeding in the alveoli. Furthermore, myrtenol increased anti-inflammatory cytokines, anti-oxidants agents, eNOS, anti-apoptotic proteins and the survival time of animals. The niosomal form of myrtenol showed a more ameliorative effect than its simple form.
The results showed the superior protective effect of the inhalation of myrtenol niosomal form against LIRI compared to its simple form and systemic use.

Lung cancer is one of the most common cancers in men. Although many diagnostic and treatment regimens have been followed in the treatment for lung cancer, increasing mortality rate due to lung cancer is depressing and hence requires alternative plant based therapeutics with with less side-effects. Myrtenol exhibits anti-inflammatory and antioxidant properties. Hence we intended to study the effect of Myrtenol on B(a)P-induced lung cancer. Our study showed that B(a)P lowered hematological count, decreased phagocyte and avidity indices, nitroblue tetrazolium (NBT) reduction, levels of immunoglubulins, antioxidant levels, whereas Myrtenol treatment restored them back to normal levels. On the other hand, xenobiotic and liver dysfunction marker enzymes and pro-inflammatory cytokines were elevated on B(a)P exposure, which retuned back to normal by Myrtenol. This study thus describes the immunomodulatory and antioxidant effects of Myrtenol on B[a]P-induced immune destruction.

Traumatic brain injury (TBI) is an important and growing cause of disability worldwide, and its cognitive consequences may be particularly significant. This study assessed the neuroprotective impacts of estradiol (E2), myrtenol (Myr), and the combination of the two on the neurological outcome, hemodynamic parameters, learning and memory, brain-derived neurotrophic factor (BDNF) level, phosphoinositide 3-kinases (PI3K/AKT) signaling, and inflammatory and oxidative factors in the hippocampus after TBI.
Eighty-four adult male Wistar rats were randomly divided into 12 groups with seven rats in each (six groups to measure intracranial pressure, cerebral perfusion pressure, brain water content, and veterinary coma scale, and six groups for behavioral and molecular studies): sham, TBI, TBI/vehicle, TBI/Myr, TBI/E2, and TBI/Myr + E2 (Myr 50 mg/kg and E2 33.3 μg/kg via inhalation for 30 min after TBI induction). Brain injury was induced by using Marmarou\'s method. Briefly, a 300-g weight was dropped down from a 2-m height through a free-falling tube onto the head of the anesthetized animals.
Veterinary coma scale, learning and memory, brain water content, intracranial pressure, and cerebral perfusion pressure were impaired following TBI, and inflammation and oxidative stress were raised in the hippocampus after TBI. The BDNF level and PI3K/AKT signaling were impaired due to TBI. Inhalation of Myr and E2 had protective effects against all negative consequences of TBI by decreasing brain edema and the hippocampal content of inflammatory and oxidant factors and also by improving BDNF and PI3K/AKT in the hippocampus. Based on these data, there were no differences between alone and combination administrations.
Our results propose that Myr and E2 have neuroprotective effects on cognition impairments due to TBI.

BACKGROUND: Asthma is related to neurochemical alterations which affect brain functions and lead to anxiety and cognitive dysfunctions. Myrtenol has sparked considerable interest due to its pharmacological effects, especially for the remediation of chronic disorders. Thus, the present research was designed to evaluate the impacts of myrtenol on anxiety-like behaviors, cognitive declines, inflammation, and oxidative stress in the hippocampus of asthmatic rats.
METHODS: Rats were allocated to five groups: control, asthma, asthma/vehicle, asthma/myrtenol, and asthma/budesonide. Asthma was elicited in the rats by ovalbumin, and the animals were then exposed to myrtenol inhalation. Anxiety-like behavior and memory were assessed by elevated plus maze (EPM) and novel object and location recognition tests. Interleukins (interleukin-6, -17, and -10), tumor necrosis factor α (TNF-α), and oxidative stress biomarkers such as malondialdehyde (MDA), superoxide dismutase (SOD), Glutathione peroxidase (GPX), and total antioxidant capacity (TAC) in the hippocampus were assessed by the ELISA method.
RESULTS: The levels of IL-6, IL-17, TNF-α, and MDA decreased, but GPX, SOD, and TAC levels increased in the hippocampus of asthmatic animals due to myrtenol inhalation.
CONCLUSIONS: Myrtenol diminished asthma-induced anxiety-like behaviors and cognitive deficits in asthmatic rats; these effects might have been typically mediated by a reduction in inflammation and oxidative stress.

Myrtenol (C10H16O) is a volatile compound belonging to the terpenoid family of monocyclic monoterpenes. It is one of the essential oils constituents of several aromatic plants, including the genera Myrtus, Tanacetum, Artemisia, Hyssopus, and Rhodiola. The oxidation of α-pinene can produce it. Several reports demonstrated the pharmacological properties of myrtenol, including its antioxidant, antibacterial, antifungal, antidiabetic, anxiolytic, and gastroprotective activities. In this review, we discussed and highlighted in depth the pharmacological activities, cellular and molecular, providing insight into the mechanisms of myrtenol. In light of this finding, the interesting biological activities and abundance of myrtenol in nature suggests its potential applications in medicinal settings in the fight against various diseases.

Infectious diseases caused by various nosocomial microorganisms affect worldwide both immunocompromised and relatively healthy persons. Bacteria and fungi have different tools to evade antimicrobials, such as hydrolysis damaging the drug, efflux systems, and the formation of biofilm that significantly complicates the treatment of the infection. Here, we show that myrtenol potentiates the antimicrobial and biofilm-preventing activity of conventional drugs against S. aureus and C. albicans mono- and dual-species cultures. In our study, the two optical isomers, (-)-myrtenol and (+)-myrtenol, have been tested as either antibacterials, antifungals, or enhancers of conventional drugs. (+)-Myrtenol demonstrated a synergistic effect with amikacin, fluconazole, and benzalkonium chloride on 64-81% of the clinical isolates of S. aureus and C. albicans, including MRSA and fluconazole-resistant fungi, while (-)-myrtenol increased the properties of amikacin and fluconazole to repress biofilm formation in half of the S. aureus and C. albicans isolates. Furthermore, myrtenol was able to potentiate benzalkonium chloride up to sixteen-fold against planktonic cells in an S. aureus-C. albicans mixed culture and repressed the adhesion of S. aureus. The mechanism of both (-)-myrtenol and (+)-myrtenol synergy with conventional drugs was apparently driven by membrane damage since the treatment with both terpenes led to a significant drop in membrane potential similar to the action of benzalkonium chloride. Thus, due to the low toxicity of myrtenol, it seems to be a promising agent to increase the efficiency of the treatment of infections caused by bacteria and be fungi of the genus Candida as well as mixed fungal-bacterial infections, including resistant strains.

The increased incidence of mixed infections requires that the scientific community develop novel antimicrobial molecules. Essential oils and their bioactive pure compounds have been found to exhibit a wide range of remarkable biological activities and are attracting more and more attention. Therefore, the aim of this study was to evaluate myrtenol (MYR), one of the constituents commonly found in some essential oils, for its potential to inhibit biofilms alone and in combination with antimicrobial drugs against Candida auris/Klebsiella pneumoniae single and mixed biofilms. The antimicrobial activity of MYR was evaluated by determining bactericidal/fungicidal concentrations (MIC), and biofilm formation at sub-MICs was analyzed in a 96-well microtiter plate by crystal violet, XTT reduction assay, and CFU counts. The synergistic interaction between MYR and antimicrobial drugs was evaluated by the checkerboard method. The study found that MYR exhibited antimicrobial activity at high concentrations while showing efficient antibiofilm activity against single and dual biofilms. To understand the underlying mechanism by which MYR promotes single/mixed-species biofilm inhibition, we observed a significant downregulation in the expression of mrkA, FKS1, ERG11, and ALS5 genes, which are associated with bacterial motility, adhesion, and biofilm formation as well as increased ROS production, which can play an important role in the inhibition of biofilm formation. In addition, the checkerboard microdilution assay showed that MYR was strongly synergistic with both caspofungin (CAS) and meropenem (MEM) in inhibiting the growth of Candida auris/Klebsiella pneumoniae-mixed biofilms. Furthermore, the tested concentrations showed an absence of toxicity for both mammalian cells in the in vitro and in vivo Galleria mellonella models. Thus, MYR could be considered as a potential agent for the management of polymicrobial biofilms.

UNASSIGNED: blaNDM-1-producing Acinetobacter baumannii (BP-AB) remains a critical problem in nosocomial infections, because of its resistance mediated by the biofilm formation and virulence factors. No studies have confirmed myrtenol\'s efficacy in inhibiting the biofilm formation and virulence associated with biofilm of BP-AB.
UNASSIGNED: The tested concentrations of myrtenol were wild type (A), 50 μg/mL (B), 100 μg/mL (C), 200 μg/mL (D), 250 μg/mL (E), and 300 μg/mL (F).
UNASSIGNED: The BP-AB biofilm inhibition was significantly higher in the D, E, and F groups than in the A, B, and C groups. Myrtenol significantly reduced the air-liquid interface ring formation in glass tubes. It also effectively inhibited the attachment of BP-AB strains on polystyrene surfaces as shown by crystal violet staining. Microscopy showed a significant reduction in biofilm formation with dispersed BP-AB strains. The confocal laser scanning microscopy analysis showed a significant reduction in the biofilm\'s biomass, covered surface area, and thickness. The scanning electron microscopy analysis revealed significantly fewer BP-AB aggregates on the coverslip surface. In the CompStat analysis, the biofilm\'s biomass, maximum thickness, and surface-to-volume ratio were significantly reduced. The qPCR analysis revealed a significant down-regulation of bfmR, bap, csuA/B, and ompA expression, which positively correlated with the biofilm\'s biomass, maximum thickness, and surface-to-volume ratio in BP-AB strains. Myrtenol significantly improved the susceptibility of BP-AB to the antibiotics amikacin, piperacillin/tazobactam, cefoperazone/sulbactam, and ceftazidime.
UNASSIGNED: Myrtenol attenuates the BP-AB biofilm formation and virulence by suppressing the expression of bfmR, bap, csuA/B, and ompA.