Limonene, a citrus monoterpene, non-complexed and complexed with hydroxypropyl-β-cyclodextrin attenuates acute and chronic orofacial nociception in rodents: Evidence for involvement of the PKA and PKC pathway

Current Combinatorial Therapeutic Aspects: The Future Prospect for Glioblastoma Treatment

There are several types of brain tumors but glioblastoma (GBM) is one of the highly malignant tumors. A primary concern with GBM is that the treatment is inadequate. Even after giving many multi-stacked combinations of therapies to patients, inclusive of chemotherapy, radiation, and surgery, the median survival rate remains poor. Due to its heterogeneous nature, the use of selective therapy for specific targeting of tumor cells is of particular importance. Although many treatment alternatives which include surgery with adjuvant chemotherapy and radiotherapy are available, the prognosis of the disease is very poor. Combination therapy is becoming the foundation of modern antitumor therapy and it is continuously evolving and developing innovative drug regimens as evidenced by ongoing preclinical and clinical trials. In this review, we discuss the current treatment options and emerging therapeutic approaches for the treatment of GBM. The prospects for alternative glioblastoma therapy are also discussed.

Enhancing orofacial pain relief: α-phellandrene complexed with hydroxypropyl-β-cyclodextrin mitigates orofacial nociception in rodents

Orofacial pain affects 10-15% of adults and can severely impact quality of life. Despite ongoing treatment challenges, monoterpene alpha-phellandrene (PHE) shows potential therapeutic benefits. This study aimed to develop and evaluate an inclusion complex of PHE with hydroxypropyl-beta-cyclodextrin (PHE-HPβCD) for treating orofacial pain. The PHE-HPβCD complex was created using physical mixing and characterized by differential scanning calorimetry (DSC) and high-performance liquid chromatography (HPLC) to determine encapsulation efficiency. The complex exhibited a 70.45% encapsulation efficiency. Male Swiss mice were used in models of orofacial pain induced by formalin, cinnamaldehyde, glutamate, and corneal nociception by hypertonic saline. Additionally, cytokine levels (TNF-α and IL-1β) were measured in the upper lip tissue of mice subjected to the formalin model. Both PHE and PHE-HPβCD showed significant antinociceptive effects at a 50 mg/kg dose during formalin-induced pain, reducing both neurogenic and inflammatory phases of pain. PHE-HPβCD also reduced TNF-α and IL-1β levels. For cinnamaldehyde and glutamate-induced nociception, both treatments reduced pain behavior, but only PHE-HPβCD decreased eye wipes in corneal nociception. These results suggest that PHE, especially in complexed form, alleviates orofacial pain by potentially modulating pain-related receptors (TRPA1 and TRPV1), mediators, like glutamate, and reducing pro-inflammatory cytokines. Further research is needed to explore the precise mechanisms of PHE in chronic orofacial pain models, but the study indicates promising avenues for new pain treatments.

CgLS mediates limonene synthesis of main essential oil component in secretory cavity cells of Citrus grandis 'Tomentosa' fruits

d-Limonene is the predominant component of essential oil from Exocarpium Citri Grandis, known for its antibacterial, antioxidant, insecticidal, and anti-inflammatory properties. The synthesis, transport, and accumulation of d-limonene in Citrus grandis 'Tomentosa' fruits are regulated by limonene synthase (LS) and its associated regulatory genes. This study addresses the gap in understanding the spatiotemporal cytological changes of LS and its regulatory genes. Through cytochemical techniques, we investigated the distribution of essential oil in the plastids, endoplasmic reticulum, and vacuoles of secretory cavity cells. We identified the LS-encoding gene CgLS via transcriptomics and demonstrated in vitro that CgLS catalyzes the formation of d-limonene from geranyl diphosphate (GPP). Transient overexpression of CgLS increased monoterpene limonene accumulation, while TRV virus-induced gene silencing reduced it. CgLS expression levels and d-limonene content showed spatiotemporal consistency with fruit development, with in situ hybridization revealing predominant expression in secretory cavity cells. Immunocytochemical localization indicated that CgLS is primarily located in the endoplasmic reticulum, plastids, and vacuoles. Our findings suggest that CgLS is translated in the endoplasmic reticulum and transported to plastids and vacuoles where d-limonene synthesis occurs. This study provides comprehensive insights into the characteristics of CgLS and its role in d-limonene synthesis at the tissue, cellular, and molecular levels in C. grandis 'Tomentosa'.

Nutritional Strategies for Chronic Craniofacial Pain and Temporomandibular Disorders: Current Clinical and Preclinical Insights

This narrative review provides an overview of current knowledge on the impact of nutritional strategies on chronic craniofacial pain associated with temporomandibular disorders (TMDs). Individuals experiencing painful TMDs alter their dietary habits, avoiding certain foods, possibly due to chewing difficulties, which might lead to nutrient deficiencies. Our literature investigation revealed that the causal links between nutritional changes and craniofacial pain remain unclear. However, clinical and preclinical studies suggest that nutraceuticals, including vitamins, minerals, polyphenols, omega-3 fatty acids, isoprenoids, carotenoids, lectins, polysaccharides, glucosamines, and palmitoylethanolamides, could have beneficial effects on managing TMDs. This is described in 12 clinical and 38 preclinical articles since 2000. Clinical articles discussed the roles of vitamins, minerals, glucosamine, and palmitoylethanolamides. The other nutraceuticals were assessed solely in preclinical studies, using TMD models, mostly craniofacial inflammatory rodents, with 36 of the 38 articles published since 2013. Our investigation indicates that current evidence is insufficient to assess the efficacy of these nutraceuticals. However, the existing data suggest potential for therapeutic intervention in TMDs. Further support from longitudinal and randomized controlled studies and well-designed preclinical investigations is necessary to evaluate the efficacy of each nutraceutical intervention and understand their underlying mechanisms in TMDs.

The protective effects of naringenin, a citrus flavonoid, non-complexed or complexed with hydroxypropyl-β-cyclodextrin against multiorgan damage caused by neonatal endotoxemia

BACKGROUND

Endotoxemia is a severe and dangerous clinical syndrome that results in elevated morbidity, especially in intensive care units. Neonates are particularly susceptible to endotoxemia due to their immature immune systems. There are few effective treatments for neonatal endotoxemia. One group of compounds with potential in the treatment of neonatal inflammatory diseases such as endotoxemia is the flavonoids, mainly due to their antioxidant and anti-inflammatory properties. Among these, naringenin (NGN) is a citrus flavonoid which has already been reported to have anti-inflammatory, antioxidant, anti-nociceptive and anti-cancer effects. Unfortunately, its clinical application is limited by its low solubility and bioavailability. However, cyclodextrins (CDs) have been widely used to improve the solubility of nonpolar drugs and enhance the bioavailability of these natural products.

OBJECTIVE

We, therefore, aimed to investigate the effects of NGN non-complexed and complexed with hydroxypropyl-β-cyclodextrin (HPβCD) on neonatal endotoxemia injuries in a rodent model and describe the probable molecular mechanisms involved in NGN activities.

METHOD

We used exposure to a bacterial lipopolysaccharide (LPS) to induce neonatal endotoxemia in the mice.

RESULTS

It was found that NGN (100 mg/kg i.p.) exposure during the neonatal period reduced leukocyte migration and decreased pro-inflammatory cytokine (TNF-α, IL-1β and IL-6) levels in the lungs, heart, kidneys or cerebral cortex. In addition, NGN upregulated IL-10 production in the lungs and kidneys of neonate mice. The administration of NGN also enhanced antioxidant enzyme catalase and SOD activity, reduced lipid peroxidation and protein carbonylation and increased the reduced sulfhydryl groups in an organ-dependent manner, attenuating the oxidative damage caused by LPS exposure. NGN decreased ERK1/2, p38MAPK and COX-2 activation in the lungs of neonate mice. Moreover, NGN complexed with HPβCD was able to increase the animal survival rate.

CONCLUSION

NGN attenuated inflammatory and oxidative damage in the lungs, heart and kidneys caused by neonatal endotoxemia through the MAPK signaling pathways regulation. Our results show that NGN has beneficial effects against neonatal endotoxemia and could be useful in the treatment of neonatal inflammatory injuries.

Therapeutic Potential of Myrtenal and Its Derivatives-A Review

The investigation of monoterpenes as natural products has gained significant attention in the search for new pharmacological agents due to their ability to exhibit a wide range in biological activities, including antifungal, antibacterial, antioxidant, anticancer, antispasmodic, hypotensive, and vasodilating properties. In vitro and in vivo studies reveal their antidepressant, anxiolytic, and memory-enhancing effects in experimental dementia and Parkinson's disease. Chemical modification of natural substances by conjugation with various synthetic components is a modern method of obtaining new biologically active compounds. The discovery of new potential drugs among monoterpene derivatives is a progressive avenue within experimental pharmacology, offering a promising approach for the therapy of diverse pathological conditions. Biologically active substances such as monoterpenes, for example, borneol, camphor, geraniol, pinene, and thymol, are used to synthesize compounds with analgesic, anti-inflammatory, anticonvulsive, antidepressant, anti-Alzheimer's, antiparkinsonian, antiviral and antibacterial (antituberculosis) properties. Myrtenal is a perspective monoterpenoid with therapeutic potential in various fields of medicine. Its chemical modifications often lead to new or more pronounced biological effects. As an example, the conjugation of myrtenal with the established pharmacophore adamantane enables the augmentation of several of its pivotal properties. Myrtenal-adamantane derivatives exhibited a variety of beneficial characteristics, such as antimicrobial, antifungal, antiviral, anticancer, anxiolytic, and neuroprotective properties, which are worth examining in more detail and at length.

Limonene, a Monoterpene, Mitigates Rotenone-Induced Dopaminergic Neurodegeneration by Modulating Neuroinflammation, Hippo Signaling and Apoptosis in Rats

Rotenone (ROT) is a naturally derived pesticide and a well-known environmental neurotoxin associated with induction of Parkinson’s disease (PD). Limonene (LMN), a naturally occurring monoterpene, is found ubiquitously in citrus fruits and peels. There is enormous interest in finding novel therapeutic agents that can cure or halt the progressive degeneration in PD; therefore, the main aim of this study is to investigate the potential neuroprotective effects of LMN employing a rodent model of PD measuring parameters of oxidative stress, neuro-inflammation, and apoptosis to elucidate the underlying mechanisms. PD in experimental rats was induced by intraperitoneal injection of ROT (2.5 mg/kg) five days a week for a total of 28 days. The rats were treated with LMN (50 mg/kg, orally) along with intraperitoneal injection of ROT (2.5 mg/kg) for the same duration as in ROT-administered rats. ROT injections induced a significant loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and DA striatal fibers following activation of glial cells (astrocytes and microglia). ROT treatment enhanced oxidative stress, altered NF-κB/MAPK signaling and motor dysfunction, and enhanced the levels/expressions of inflammatory mediators and proinflammatory cytokines in the brain. There was a concomitant mitochondrial dysfunction followed by the activation of the Hippo signaling and intrinsic pathway of apoptosis as well as altered mTOR signaling in the brain of ROT-injected rats. Oral treatment with LMN corrected the majority of the biochemical, pathological, and molecular parameters altered following ROT injections. Our study findings demonstrate the efficacy of LMN in providing protection against ROT-induced neurodegeneration.