Zicam-induced damage to mouse and human nasal tissue

Safety Assessment of Zinc Salts as Used in Cosmetics

The Expert Panel for Cosmetic Ingredient Safety (Panel) assessed the safety of 27 inorganic and organometallic zinc salts as used in cosmetic formulations; these salts are specifically of the 2+ (II) oxidation state cation of zinc. These ingredients included in this report have various reported functions in cosmetics, including hair conditioning agents, skin conditioning agents, cosmetic astringents, cosmetic biocides, preservatives, oral care agents, buffering agents, bulking agents, chelating agents, and viscosity increasing agents. The Panel reviewed the relevant data for these ingredients, and concluded that these 27 ingredients are safe in cosmetics in the present practices of use and concentration described in this safety assessment when formulated to be non-irritating.

Blocking olfactory input alters aggression in male and female California mice (Peromyscus californicus)

Olfactory input into the brain can be disrupted by a variety of environmental factors, including exposure to pathogens or environmental contaminants. Olfactory cues are often eliminated in laboratory rats and mice through highly invasive procedures like olfactory bulbectomy, which may also disrupt accessory olfactory pathways and detection of non-volatile odors. In the present study, we tested whether inducing anosmia through intranasal infusion of zinc gluconate alters aggression in a monogamous, biparental rodent species, the California mouse (Peromyscus californicus). This less invasive method of manipulating olfaction selectively targets the olfactory epithelium and reduces the detection of volatile odors. Treatment with zinc gluconate extended the time required for male and female California mice to find hidden pieces of apple and reduced the amount of time spent investigating bedding that was soiled by unfamiliar males. Moreover, inhibition of olfaction with zinc gluconate reduced aggressiveness in both sexes as demonstrated by an increased attack latency in the resident-intruder test among same-sex dyads from the same treatment group. These results suggest that volatile olfactory cues are necessary for agonistic responses in both male and female California mice. Therefore, even in species with complex social systems that include territorial aggression and monogamy, volatile olfactory cues modulate agonistic behavior.

Olfaction and Melatonin: The Use of the Olfactory Discrimination Test

In order to investigate the role of melatonin in olfactory function, we present the olfactory discrimination test as a simple and low-cost behavioral assessment. The test consists in evaluating the time that each rat spent in two compartments: one has a familiar odor (sawdust with the smell from the animal) and the other one with an unfamiliar odor (clean sawdust). Animals with the normal olfactory functions will discriminate between these two odors and will spend more time in the familiar compartment. We used the olfactory discrimination test to evaluate the role of melatonin receptors expressed in the olfactory bulb of rats. In a previous study, our results have successfully detected an olfactory modulation, by mean of the olfactory discrimination test, promoted by the infusion of melatonin receptor ligands into the olfactory bulb of rats.

Harm as a Necessary Component of the Concept of Medical Disorder: Reply to Muckler and Taylor

Wakefield's harmful dysfunction analysis asserts that the concept of medical disorder includes a naturalistic component of dysfunction (failure of biologically designed functioning) and a value (harm) component, both of which are required for disorder attributions. Muckler and Taylor, defending a purely naturalist, value-free understanding of disorder, argue that harm is not necessary for disorder. They provide three examples of dysfunctions that, they claim, are considered disorders but are entirely harmless: mild mononucleosis, cowpox that prevents smallpox, and minor perceptual deficits. They also reject the proposal that dysfunctions need only be typically harmful to qualify as disorders. We argue that the proposed counterexamples are, in fact, considered harmful; thus, they fail to disconfirm the harm requirement: incapacity for exertion is inherently harmful, whether or not exertion occurs, cowpox is directly harmful irrespective of indirect benefits, and colorblindness and anosmia are considered harmful by those who consider them disorders. We also defend the typicality qualifier as viably addressing some apparently harmless disorders and argue that a dysfunction's harmfulness is best understood in dispositional terms.

Adverse Events Associated with Intranasal Sprays: An Analysis of the Food and Drug Administration Database and Literature Review

BACKGROUND

Intranasal sprays (INSs) are commonly used medications for the treatment of many rhinologic conditions. Despite their popularity, an analysis of a nationwide reporting database and comparison to the available literature has never been performed.

METHODS

The Food and Drug Administration Adverse Event Reporting System (FAERS) database was accessed to obtain adverse event (AE) records from 2014 to 2019 for varying INSs, including: 10 corticosteroids, 1 alpha adrenergic, and 3 antihistamines. The Proportional Reporting Ratios (PRR) and Reporting Odds Ratios (ROR) were calculated for dyspnea, anosmia, ageusia/dysgeusia, epistaxis, and headache. A PRR ≥ 2 or ROR ≥ 1 was considered significant.

RESULTS

Corticosteroids had 98 864 total reported AEs to the database, followed by antihistamines (7011) and alpha adrenergics (2071). In total, dyspnea was reported 5843 times, followed by headache (4230), epistaxis (1205), ageusia/dysgeusia (920), and anosmia (312). Overall, PRR and ROR values for dyspnea ranged from 0.51 to 4.25 and 0.51 to 4.49; for dysgeusia/ageusia from 0.56 to 6.09 and 0.56 to 6.12; and for epistaxis from 1.03 to 27.24 and 1.03 to 30.76, respectively. All medications which listed anosmia within the top AEs had PRR and ROR values exceeding 2 and 1, respectively. The PRR for headache exceeded 2 for 1 medication and the ROR exceeded 1 in 7 medications.

CONCLUSION

The AEs of dyspnea, anosmia, ageusia/dysgeusia, epistaxis, and headache are reported within the FAERS database for commonly prescribed INSs. When compared against the existing scientific literature, the clinical significance of this reporting tool from the FDA for these classes of medications remains unvalidated.

General Aspects of Metal Ions as Signaling Agents in Health and Disease

This review focuses on the current knowledge on the involvement of metal ions in signaling processes within the cell, in both physiological and pathological conditions. The first section is devoted to the recent discoveries on magnesium and calcium-dependent signal transduction-the most recognized signaling agents among metals. The following sections then describe signaling pathways where zinc, copper, and iron play a key role. There are many systems in which changes in intra- and extra-cellular zinc and copper concentrations have been linked to important downstream events, especially in nervous signal transduction. Iron signaling is mostly related with its homeostasis. However, it is also involved in a recently discovered type of programmed cell death, ferroptosis. The important differences in metal ion signaling, and its disease-leading alterations, are also discussed.

The Olfactory System of Zebrafish as a Model for the Study of Neurotoxicity and Injury: Implications for Neuroplasticity and Disease

The olfactory system, composed of the olfactory organs and the olfactory bulb, allows organisms to interact with their environment and through the detection of odor signals. Olfaction mediates behaviors pivotal for survival, such as feeding, mating, social behavior, and danger assessment. The olfactory organs are directly exposed to the milieu, and thus are particularly vulnerable to damage by environmental pollutants and toxicants, such as heavy metals, pesticides, and surfactants, among others. Given the widespread occurrence of olfactory toxicants, there is a pressing need to understand the effects of these harmful compounds on olfactory function. Zebrafish (Danio rerio) is a valuable model for studying human physiology, disease, and toxicity. Additionally, the anatomical components of the zebrafish olfactory system are similar to those of other vertebrates, and they present a remarkable degree of regeneration and neuroplasticity, making it an ideal model for the study of regeneration, reorganization and repair mechanisms following olfactory toxicant exposure. In this review, we focus on (1) the anatomical, morphological, and functional organization of the olfactory system of zebrafish; (2) the adverse effects of olfactory toxicants and injury to the olfactory organ; and (3) remodeling and repair neuroplasticity mechanisms following injury and degeneration by olfactory toxicant exposure.

Olfactory dysfunction revisited: a reappraisal of work-related olfactory dysfunction caused by chemicals

Occupational exposure to numerous individual chemicals has been associated with olfactory dysfunction, mainly in individual case descriptions. Comprehensive epidemiological investigations into the olfactotoxic effect of working substances show that the human sense of smell may be impaired by exposure to metal compounds involving cadmium, chromium and nickel, and to formaldehyde. This conclusion is supported by the results of animal experiments. The level of evidence for a relationship between olfactory dysfunction and workplace exposure to other substances is relatively weak.

Olfactory dysfunction revisited: a reappraisal of work-related olfactory dysfunction caused by chemicals

Occupational exposure to numerous individual chemicals has been associated with olfactory dysfunction, mainly in individual case descriptions. Comprehensive epidemiological investigations into the olfactotoxic effect of working substances show that the human sense of smell may be impaired by exposure to metal compounds involving cadmium, chromium and nickel, and to formaldehyde. This conclusion is supported by the results of animal experiments. The level of evidence for a relationship between olfactory dysfunction and workplace exposure to other substances is relatively weak.

Dopaminergic Lesion in the Olfactory Bulb Restores Olfaction and Induces Depressive-Like Behaviors in a 6-OHDA Model of Parkinson's Disease

Olfactory impairments and depressive behavior are commonly reported by individuals with Parkinson's disease (PD) being observed before motor symptoms. The mechanisms underlying these clinical manifestations are not fully elucidated. However, the imbalance in dopaminergic neurotransmission seems to play an important role in this context. In patients and animal models of PD, an increase in the dopaminergic interneurons of the glomerular layer in olfactory bulb (OB-gl) is observed, which may contribute to the olfactory impairment. In addition, neuronal imbalance in OB is related to depressive symptoms, as demonstrated by chemical olfactory bulbectomy. In view of that, we hypothesized that a reduction in the number or density of dopaminergic neurons present in OB could promote an olfactory improvement and, in contrast, would accentuate the depressive-like behaviors in the 6-hydroxydopamine (6-OHDA) model of PD. Therefore, we performed single or double injections of 6-OHDA within the substantia nigra pars compacta (SNpc) and/or in the OB-gl. We observed that, after 7 days, the group with nigral lesion exhibited olfactory impairment, as well as the group with the lesion in the OB-gl. However, the combination of the lesions prevented the occurrence of hyposmia. In relation to depressive-like behaviors, we observed that the SNpc injury promoted depressive-like behavior, being accentuated after a double injury. Our results demonstrated the importance of the dopaminergic neurons of the OB-gl in different non-motor features of PD, since the selective reduction of these periglomerular neurons was able to induce olfactory impairment and depressive-like behaviors.

Nose-to-brain delivery of insulin enhanced by a nanogel carrier

Recent evidences suggest that insulin delivery to the brain can be an important pharmacological therapy for some neurodegenerative pathologies, including Alzheimer disease (AD). Due to the presence of the Blood Brain Barrier, a suitable carrier and an appropriate route of administration are required to increase the efficacy and safety of the treatment. Here, poly(N-vinyl pyrrolidone)-based nanogels (NG), synthetized by e-beam irradiation, alone and with covalently attached insulin (NG-In) were characterized for biocompatibility and brain delivery features in a mouse model. Preliminarily, the biodistribution of the "empty" nanocarrier after intraperitoneal (i.p.) injection was investigated by using a fluorescent-labeled NG. By fluorescence spectroscopy, SEM and dynamic light scattering analyses we established that urine clearance occurs in 24h. Histological liver and kidneys inspections indicated that no morphological alterations of tissues occurred and no immunological response was activated after NG injection. Furthermore, after administration of the insulin-conjugated nanogels (NG-In) through the intranasal route (i.n.) no alteration or immunogenic response of the nasal mucosa was observed, suggesting that the formulation is well tolerated in mouse. Moreover, an enhancement of NG-In delivery to the different brain areas and of its biological activity, measured as Akt activation levels, with reference to free insulin administration was demonstrated. Taken together, these results indicate that the synthesized NG-In enhances brain insulin delivery upon i.n. administration and strongly encourage its further evaluation as therapeutic agent against some neurodegenerative diseases.

15th Annual Meeting of the Safety Pharmacology Society: Focus on traditional sensory systems

INTRODUCTION

This report summarizes and comments key talks on the five traditional senses (ear, vestibular system, vision, taste, olfaction, and touch) which were delivered during the 2015 Annual Meeting of the Safety Pharmacology (SP) Society.

AREAS COVERED

The functional observational battery (FOB) can detect major candidate drug liabilities only on ear, touch and vision. Anatomy, physiology, pharmacology, and pathology notions on each sensory system introduce speaker talks. Techniques for evaluating drug effects on hearing functions are reviewed. Nonclinical approaches to assess vestibular toxicity leading to balance deficits are presented. Retinal explants studied with multielectrode arrays allow the identification of drug liability sites on the retina. Routinely performed Safety Pharmacology assays are not powered to address candidate drug-induced disturbances on taste and smell. This weakness needs correction since unintended pharmacological impairment of these sensorial functions may have serious health consequences. Neuropathy produced by chemotherapeutic agents may cause multiple sensorial perception distortions.

CONCLUSIONS

Safety Pharmacology studies should ensure the safety of any candidate drug on the five sensorial systems.

Exposure to Zinc Sulfate Results in Differential Effects on Olfactory Sensory Neuron Subtypes in Adult Zebrafish

Zinc sulfate is a known olfactory toxicant, although its specific effects on the olfactory epithelium of zebrafish are unknown. Olfactory organs of adult zebrafish were exposed to zinc sulfate and, after 2, 3, 5, 7, 10 or 14 days, fish were processed for histological, immunohistochemical, ultrastructural, and behavioral analyses. Severe morphological disruption of the olfactory organ was observed two days following zinc sulfate exposure, including fusion of lamellae, epithelial inflammation, and significant loss of anti-calretinin labeling. Scanning electron microscopy revealed the apical surface of the sensory region was absent of ciliated structures, but microvilli were still present. Behavioral analysis showed significant loss of the ability to perceive bile salts and some fish also had no response to amino acids. Over the next several days, olfactory organ morphology, epithelial structure, and anti-calretinin labeling returned to control-like conditions, although the ability to perceive bile salts remained lost until day 14. Thus, exposure to zinc sulfate results in rapid degeneration of the olfactory organ, followed by restoration of morphology and function within two weeks. Zinc sulfate appears to have a greater effect on ciliated olfactory sensory neurons than on microvillous olfactory sensory neurons, suggesting differential effects on sensory neuron subtypes.

Impact of Single or Repeated Dose Intranasal Zinc-free Insulin in Young and Aged F344 Rats on Cognition, Signaling, and Brain Metabolism

Novel therapies have turned to delivering compounds to the brain using nasal sprays, bypassing the blood brain barrier, and enriching treatment options for brain aging and/or Alzheimer's disease. We conducted a series of in vivo experiments to test the impact of intranasal Apidra, a zinc-free insulin formulation, on the brain of young and aged F344 rats. Both single acute and repeated daily doses were compared to test the hypothesis that insulin could improve memory recall in aged memory-deficient animals. We quantified insulin signaling in different brain regions and at different times following delivery. We measured cerebral blood flow (CBF) using MRI and also characterized several brain metabolite levels using MR spectroscopy. We show that neither acute nor chronic Apidra improved memory or recall in young or aged animals. Within 2 hours of a single dose, increased insulin signaling was seen in ventral areas of the aged brains only. Although chronic Apidra was able to offset reduced CBF with aging, it also caused significant reductions in markers of neuronal integrity. Our data suggest that this zinc-free insulin formulation may actually hasten cognitive decline with age when used chronically.

Current understanding of nasal morphology and physiology as a drug delivery target

The nasal cavity is both a target for locally and systemically acting medications. An adequate treatment for rhinosinusitis continues to be an unmet need. With the recent approval of intranasal medications for the treatment of pain, the nasal cavity continues to be a viable route for rapid uptake into the systemic circulation. Despite the opportunities, there is still a void in the knowledge of how therapeutic entities interact with the nasal epithelium. In addition, new opportunities in mucosal immunity via nasal vaccination as well as the elusive nose to brain uptake continue to drive innovation. To facilitate understanding of the issues involved that facilitate drug delivery in the nose, a review of nasal morphology and physiology is presented.

Olfactory impairment in the rotenone model of Parkinson's disease is associated with bulbar dopaminergic D2 activity after REM sleep deprivation

Olfactory and rapid eye movement (REM) sleep deficits are commonly found in untreated subjects with a recent diagnosis of Parkinson's disease (PD). Additionally, different studies report declines in olfactory performance during a short period of sleep deprivation. Mechanisms underlying these clinical manifestations are poorly understood, and impairment of dopamine (DA) neurotransmission in the olfactory bulb and the nigrostriatal pathway may have important roles in olfaction and REM sleep disturbances. Therefore, we hypothesized that modulation of the dopaminergic D2 receptors in the olfactory bulb could provide a more comprehensive understanding of the olfactory deficits in PD and REM sleep deprivation (REMSD). We decided to investigate the olfactory, neurochemical, and histological alterations generated through the administration of piribedil (a selective D2 agonist) or raclopride (a selective D2 antagonist) within the glomerular layer of the olfactory bulb, in rats subjected to intranigral rotenone and REMSD. Our findings provide evidence of the occurrence of a negative correlation (r = -0.52, P = 0.04) between the number of periglomerular TH-ir neurons and the bulbar levels of DA in the rotenone, but not sham, groups. A significant positive correlation (r = 0.34, P = 0.03) was observed between nigrostriatal DA levels and olfactory discrimination index (DI) for the sham groups, indicating that increased DA levels in the substantia nigra pars compacta (SNpc) are associated with enhanced olfactory discrimination performance. Also, increased levels in bulbar and striatal DA were induced by piribedil in the rotenone control and rotenone REMSD groups, consistent with reductions in the DI. The present evidence reinforce the idea that DA produced by periglomerular neurons, particularly the bulbar dopaminergic D2 receptors, is an essential participant in olfactory discrimination processes, as the SNpc, and the striatum.

Genomics of mature and immature olfactory sensory neurons

The continuous replacement of neurons in the olfactory epithelium provides an advantageous model for investigating neuronal differentiation and maturation. By calculating the relative enrichment of every mRNA detected in samples of mature mouse olfactory sensory neurons (OSNs), immature OSNs, and the residual population of neighboring cell types, and then comparing these ratios against the known expression patterns of >300 genes, enrichment criteria that accurately predicted the OSN expression patterns of nearly all genes were determined. We identified 847 immature OSN-specific and 691 mature OSN-specific genes. The control of gene expression by chromatin modification and transcription factors, and neurite growth, protein transport, RNA processing, cholesterol biosynthesis, and apoptosis via death domain receptors, were overrepresented biological processes in immature OSNs. Ion transport (ion channels), presynaptic functions, and cilia-specific processes were overrepresented in mature OSNs. Processes overrepresented among the genes expressed by all OSNs were protein and ion transport, ER overload response, protein catabolism, and the electron transport chain. To more accurately represent gradations in mRNA abundance and identify all genes expressed in each cell type, classification methods were used to produce probabilities of expression in each cell type for every gene. These probabilities, which identified 9,300 genes expressed in OSNs, were 96% accurate at identifying genes expressed in OSNs and 86% accurate at discriminating genes specific to mature and immature OSNs. This OSN gene database not only predicts the genes responsible for the major biological processes active in OSNs, but also identifies thousands of never before studied genes that support OSN phenotypes.

Anosmia does not impair the anxiolytic-like effect of lavender essential oil inhalation in mice

AIM

The inhalation of Lavandula angustifolia (lavender) essential oil has anxiolytic-like effects in animal models and humans, but its mechanism of action is still not fully understood. The inhalation of essential oils can induce anxiolytic effects through the central nervous system (e.g., lung absorption and bloodstream transport) or stimulation of the olfactory system and secondary activation of brain regions. Thus, the main objective of the present study was to evaluate whether the perception of lavender essential oil aroma, when inhaled, is necessary to obtain its anxiolytic-like effects in mice tested in the marble-burying test.

MAIN METHODS

Anosmia was induced by irrigating the nasal cavity with zinc gluconate+zinc acetate so that the mice could not detect odors in the olfactory discrimination test. The marble-burying test was used to evaluate the anxiolytic-like effects of inhaled lavender essential oil.

KEY FINDINGS

Anosmia did not interfere with the anxiolytic-like effect of lavender essential oil inhalation in the marble-burying test at concentrations of 2.5% (number of marbles buried: vehicle, 4.7±1.0; zinc, 6.2±2.2; p>0.10) and 5% (number of marbles buried: vehicle, 3.4±0.8; zinc, 4.3±0.9; p>0.10). Lavender essential oil at a concentration of 0.5% was ineffective.

SIGNIFICANCE

These results suggest that olfactory system activation is unlikely to participate in the anxiolytic-like effect of lavender essential oil inhalation.

Nasal gel and olfactory cleft

OBJECTIVE

To evaluate whether a nasal gel, administrated using a radial-hole inhaler, reaches the olfactory cleft and if a different administration method influences distribution.

MATERIAL AND METHOD

Sixteen healthy volunteers underwent a nasal endoscopy at 1 and 7minutes after the administration of a intranasal gel, with a different method in each fossa.

RESULTS

No dye deposition was identified at the olfactory cleft, middle turbinate or middle meatus. In all cases the gel was identified at the nasal vestibule. On the right side, the second most frequent dye identification area was the inferior turbinate, with a rate of 87% at the first minute and 75% at 7 minutes. It was followed by the septum (75 and 62%) and the inferior meatus (6.2 and 12.5%). On the left side, the second most frequent stained area was the septum (18.7 and 13.5%), followed by the inferior meatus (6.5 and 65%). No inferior turbinate staining was found in the left side. There was a significant difference in the deposition rate at the septum (P<.01) and inferior turbinate (P<.001), when both administration methods were compared.

CONCLUSIONS

No nasal gel, administrated using a radial-hole inhaler, was found at the olfactory cleft, middle turbinate or middle meatus. Gel distribution was located at the anterior and inferior portion of the nose, independent of the administration method used. Significantly different gel distribution rates were found at the septum and inferior turbinate when the 2 administration methods were compared.

Human sinonasal explant system for testing cytotoxicity of intranasal agents

BACKGROUND

Intranasal agents play a critical role in the management of sinonasal disorders. There are ongoing efforts to develop new intranasal medications to combat sinonasal disease. Some intranasal agents, however, can have cytotoxic effects on human sinonasal tissue. In order to facilitate safe drug discovery, we developed a simple and reliable in vitro screening assay using human sinonasal explants to measure the cytotoxic profiles of intranasal agents.

METHODS

We obtained sinonasal tissues from several regions of the nasal cavity from 12 patients undergoing endoscopic sinonasal surgery. These tissues were cultured on polytetrafluoroethylene membrane in serum-free growth medium. We determined the biochemical properties of these explants by measuring extracellular lactate dehydrogenase (LDH) levels and performing histological analyses over a period of 1 to 2 weeks. We then examined the cytotoxic profiles of 13 intranasal agents by measuring extracellular LDH levels using the human sinonasal explant system.

RESULTS

Sinonasal explants exhibited a rapid reduction in extracellular LDH levels indicating stabilization in the culture environment within 2 days. Histological analysis showed maintenance of good cellular architecture for up to 2 weeks. The explants displayed intact epithelium and expressed βIII-tubulin and Ki-67. Of the 13 tested intranasal agents, 1% zinc sulfate (ZnSO(4) ), 5% ZnSO(4) , and Zicam application were cytotoxic.

CONCLUSION

Based on the unique biochemical properties of the human nasal explant culture system, we developed a simple and reliable in vitro screening assay to determine the cytotoxic profiles of various intranasal agents by examining extracellular LDH levels and histopathology.

Effects of zinc gluconate and 2 other divalent cationic compounds on olfactory function in mice

Intranasal application of zinc gluconate has commonly been used to treat the common cold. The safety of this treatment, however, has come into question recently. In addition to a United States recall of a homeopathic product that contains zinc gluconate, abundant literature reports cytotoxic effects of zinc on the olfactory epithelium. Additional research suggests that divalent cations (such as zinc) can block ion channels that facilitate the transduction of odors into electrical signals on the olfactory epithelium. The purpose of the current study was 2-fold: to confirm whether zinc gluconate causes anosmia and to reveal whether any other divalent cationic compounds produce a similar effect. Groups of mice underwent a buried food-pellet test to gauge olfactory function and then were nasally irrigated with 1 of 3 divalent cationic compounds. When tested after treatment, mice irrigated with zinc gluconate and copper gluconate experienced a marked increase in food-finding time, indicating that they had lost their ability to smell a hidden food source. Control mice irrigated with saline had a significantly lower increase in times. These results confirm that zinc gluconate can cause anosmia and reveal that multiple divalent cations can negatively affect olfaction.