Mitochondrial KATP channels contribute to the protective effects of hydrogen sulfide against impairment of central chemoreception of rat offspring exposed to maternal cigarette smoke.

We previously reported that maternal cigarette smoke (CS) exposure resulted in impairment of central chemoreception and induced mitochondrial dysfunction in offspring parafacial respiratory group (pFRG), the kernel for mammalian central chemoreception. We also found that hydrogen sulfide (H2S) could attenuate maternal CS exposure-induced impairment of central chemoreception in the rat offspring in vivo. Mitochondrial ATP sensitive potassium (mitoKATP) channel has been reported to play a significant role in mitochondrial functions and protect against apoptosis in neurons. Thus, we hypothesize here that mitoKATP channel plays a role in the protective effects of H2S on neonatal central chemoreception in maternal CS-exposed rats. Our findings revealed that pretreatment with NaHS (donor of H2S, 22.4mM) reversed the central chemosensitivity decreased by maternal CS exposure, and also inhibited cell apoptosis in offspring pFRG, however, 5-HD (blocker of mitoKATP channels, 19mM) attenuated the protective effects of NaHS. In addition, NaHS declined pro-apoptotic proteins related to mitochondrial pathway apoptosis in CS rat offspring pFRG, such as Bax, Cytochrome C, caspase9 and caspase3. NaHS or 5-HD alone had no significant effect on above indexes. These results suggest that mitoKATP channels play an important role in the protective effect of H2S against impairment of central chemoreception via anti-apoptosis in pFRG of rat offspring exposed to maternal CS.

Succinate Produced by Intestinal Microbes Promotes Specification of Tuft Cells to Suppress Ileal Inflammation.

BACKGROUND & AIMS: Countries endemic for parasitic infestations have a lower incidence of Crohn's disease (CD) than nonendemic countries, and there have been anecdotal reports of the beneficial effects of helminths in CD patients. Tuft cells in the small intestine sense and direct the immune response against eukaryotic parasites. We investigated the activities of tuft cells in patients with CD and mouse models of intestinal inflammation. METHODS: We used microscopy to quantify tuft cells in intestinal specimens from patients with ileal CD (n = 19), healthy individuals (n = 14), and TNFΔARE/+ mice, which develop Crohn's-like ileitis. We performed single-cell RNA sequencing, mass spectrometry, and microbiome profiling of intestinal tissues from wild-type and Atoh1-knockout mice, which have expansion of tuft cells, to study interactions between microbes and tuft cell populations. We assessed microbe dependence of tuft cell populations using microbiome depletion, organoids, and microbe transplant experiments. We used multiplex imaging and cytokine assays to assess alterations in inflammatory response following expansion of tuft cells with succinate administration in TNFΔARE/+ and anti-CD3E CD mouse models. RESULTS: Inflamed ileal tissues from patients and mice had reduced numbers of tuft cells, compared with healthy individuals or wild-type mice. Expansion of tuft cells was associated with increased expression of genes that regulate the tricarboxylic acid cycle, which resulted from microbe production of the metabolite succinate. Experiments in which we manipulated the intestinal microbiota of mice revealed the existence of an ATOH1-independent population of tuft cells that was sensitive to metabolites produced by microbes. Administration of succinate to mice expanded tuft cells and reduced intestinal inflammation in TNFΔARE/+ mice and anti-CD3E-treated mice, increased GATA3+ cells and type 2 cytokines (IL22, IL25, IL13), and decreased RORGT+ cells and type 17 cytokines (IL23) in a tuft cell-dependent manner. CONCLUSIONS: We found that tuft cell expansion reduced chronic intestinal inflammation in mice. Strategies to expand tuft cells might be developed for treatment of CD.

The Effects of Population Density on the Incidence of Developmental Deformities in Chemosensory Organs of Tobacco Hornworm Larvae (Lepidoptera: Sphingidae).

Cultures of Manduca sexta Johanssen in our laboratory were found to have larvae with missing or deformed mouthparts or antennae. Hypothesizing that these developmental deformities were caused by crowded rearing conditions, we reared larvae in four different population densities and recorded the incidence (% of larvae affected) and types of chemoreceptor deformities. Results showed that the incidence of these deformities was directly proportional to larval population density. Deformities of the maxilla and palp were the most frequent, followed by those of the antenna, epipharynx and maxillary styloconica. Life history traits of larval mass, food consumption, and rate of development were inversely related to larval density for both normal and deformed larvae. We discuss possible causes and mechanisms of these deformities and of changes to life history traits.

Breathing regulation and blood gas homeostasis after near complete lesions of the retrotrapezoid nucleus in adult rats.

KEY POINTS: The retrotrapezoid nucleus (RTN) drives breathing proportionally to brain PCO2 but its role during various states of vigilance needs clarification. Under normoxia, RTN lesions increased the arterial PCO2 set-point, lowered the PO2 set-point and reduced alveolar ventilation relative to CO2 production. Tidal volume was reduced and breathing frequency increased to a comparable degree during wake, slow-wave sleep and REM sleep. RTN lesions did not produce apnoeas or disordered breathing during sleep. RTN lesions in rats virtually eliminated the central respiratory chemoreflex (CRC) while preserving the cardiorespiratory responses to hypoxia; the relationship between CRC and number of surviving RTN Nmb neurons was an inverse exponential. The CRC does not function without the RTN. In the quasi-complete absence of the RTN and CRC, alveolar ventilation is reduced despite an increased drive to breathe from the carotid bodies. ABSTRACT: The retrotrapezoid nucleus (RTN) is one of several CNS nuclei that contribute, in various capacities (e.g. CO2 detection, neuronal modulation) to the central respiratory chemoreflex (CRC). Here we test how important the RTN is to PCO2 homeostasis and breathing during sleep or wake. RTN Nmb-positive neurons were killed with targeted microinjections of substance P-saporin conjugate in adult rats. Under normoxia, rats with large RTN lesions (92 ± 4% cell loss) had normal blood pressure and arterial pH but were hypoxic (-8 mmHg PaO2 ) and hypercapnic (+10 mmHg ). In resting conditions, minute volume (VE ) was normal but breathing frequency (fR ) was elevated and tidal volume (VT ) reduced. Resting O2 consumption and CO2 production were normal. The hypercapnic ventilatory reflex in 65% FiO2 had an inverse exponential relationship with the number of surviving RTN neurons and was decreased by up to 92%. The hypoxic ventilatory reflex (HVR; FiO2 21-10%) persisted after RTN lesions, hypoxia-induced sighing was normal and hypoxia-induced hypotension was reduced. In rats with RTN lesions, breathing was lowest during slow-wave sleep, especially under hyperoxia, but apnoeas and sleep-disordered breathing were not observed. In conclusion, near complete RTN destruction in rats virtually eliminates the CRC but the HVR persists and sighing and the state dependence of breathing are unchanged. Under normoxia, RTN lesions cause no change in VE but alveolar ventilation is reduced by at least 21%, probably because of increased physiological dead volume. RTN lesions do not cause sleep apnoea during slow-wave sleep, even under hyperoxia.

Gastric tuft cells express DCLK1 and are expanded in hyperplasia.

Epithelial tuft cells are named after their characteristic microtubule bundles located at the cell apex where these are exposed to the luminal environment. As such, tuft cells are found in multiple organs, including the gastrointestinal (GI) tract where the apical "tuft" is hypothesized to detect and transmit environmental signals. Thus, the goal of our study was to characterize gastric tuft cells during GI tract development, then subsequently in the normal and metaplastic adult stomach. GI tracts from mouse embryos, and newborn and postnatal mice were analyzed. Tuft cells were identified by immunohistochemistry using acetylated-α-tubulin (acTub) antibody to detect the microtubule bundle. Additional tuft cell markers, e.g., doublecortin-like kinase 1 (DCLK1), were used to co-localize with acTub. Tuft cells were quantified in human gastric tissue arrays and in mouse stomachs with or without inflammation. In the developing intestine, tuft cells in both the crypts and villi expressed all markers by E18.5. In the stomach, acTub co-localized with DCLK1 and other established tuft cell markers by E18.5 in the antrum, but not until postnatal day 7 in the corpus, with the highest density of tuft cells clustered at the forestomach ridge. Tuft cell numbers increased in hyperplastic human and mouse stomachs. In the adult GI tract, the tuft cell marker acTub co-expressed with DCKL1 and chemosensory markers, e.g.,TRPM5. In summary, tuft cells appear in the gastric antrum and intestine at E18.5, but their maximal numbers in the corpus are not achieved until after weaning. Tuft cell numbers increase with inflammation, hyperplasia, and metaplasia.

Hyperoxic chemoreflex sensitivity is impaired in patients with neurocardiogenic syncope.

BACKGROUND: During the development of neurocardiogenic syncope (NCS) postural dependant venous blood pooling sets off a cascade of autonomic reflexes. This causes an initial rise in sympathetic tone, which is followed by an overshoot parasympathetic activation resulting in systemic vasodilatation and/or sinus bradycardia. However, other factors like associated hyperventilation or changes in blood gas content may also contribute to syncope. Hyperoxic cardiac chemoreflex sensitivity (CHRS) is an autonomic functional test that describes the heart rate decrease in response to increases in blood oxygen content. The purpose of this study was to investigate whether CHRS is altered in NCS. METHODS AND RESULTS: CHRS was compared in 16 NCS patients (49+/-4 yr old) vs. 16 age and gender matched controls (53+/-2 yr old). NCS was verified by clinical syncope and positive head-up tilt testing. The hyperoxic CHRS was measured by determination of the venous partial pressure of oxygen and heart rate before and after 5 min of pure oxygen inhalation. The difference of the R-R intervals before and after oxygen inhalation divided by the difference in the oxygen pressures were calculated as hyperoxic chemoreflex sensitivity [ms/mm Hg]. CHRS in the control group was 7.1+/-1.1 ms/mm Hg. By contrast, CHRS in NCS patients was significantly lower (2.8+/-1.0 ms/mm Hg; p<0.05). CONCLUSION: Neurocardiogenic syncope is associated with decreased hyperoxic cardiac chemoreflex sensitivity possibly reflecting impaired deactivation of arterial chemoreceptors. The clinical and pathophysiologic importance of chemosensor function in neurocardiogenic syncope needs to be investigated in more detail.

Cholangiocyte primary cilia in liver health and disease.

The epithelial cells lining intrahepatic bile ducts (i.e., cholangiocytes), like many cell types in the body, have primary cilia extending from the apical plasma membrane into the bile ductal lumen. Cholangiocyte cilia express proteins such as polycystin-1, polycystin-2, fibrocystin, TRPV4, P2Y12, AC6, that account for ciliary mechano-, osmo-, and chemo-sensory functions; when these processes are disturbed by mutations in genes encoding ciliary-associated proteins, liver diseases (i.e., cholangiociliopathies) result. The cholangiociliopathies include but are not limited to cystic and fibrotic liver diseases associated with mutations in genes encoding polycystin-1, polycystin-2, and fibrocystin. In this review, we discuss the functions of cholangiocyte primary cilia, their role in the cholangiociliopathies, and potential therapeutic approaches.

Chronic hypoxia-induced morphological and neurochemical changes in the carotid body.

The carotid body (CB) plays an important role in the control of ventilation. Type I cells in CB are considered to be the chemoreceptive element which detects the levels of PO(2), PCO(2), and [H(+)] in the arterial blood. These cells originate from the neural crest and appear to retain some neuronal properties. They are excitable and produce a number of neurochemicals. Some of these neurochemicals, such as dopamine and norepinephrine, are considered to be primarily inhibitory to CB function and others, such as adenosine triphosphate, acetylcholine, and endothelin, are thought to be primarily excitatory. Chronic hypoxia (CH) induces profound morphological as well as neurochemical changes in the CB. CH enlarges the size of CB and causes hypertrophy and mitosis of type I cells. Also, CH changes the vascular structure of CB, including inducing marked vasodilation and the growth of new blood vessels. Moreover, CH upregulates certain neurochemical systems within the CB, e.g., tyrosine hydroxylase and dopaminergic activity in type I cells. There is also evidence that CH induces neurochemical changes within the innervation of the CB, e.g., nitric oxide synthase. During CH the sensitivity of the CB chemoreceptors to hypoxia is increased but the mechanisms by which the many CH-induced structural and neurochemical changes affect the sensitivity of CB to hypoxia remains to be established.

Sickle cells and sudden death: morphologic abnormalities of the cardiac conduction system.

Sudden unexpected death has become increasingly recognized as an important clinical feature of both homozygous and heterozygous sickling syndromes, but the exact nature of its cause has remained unexplained. We have conducted special postmortem examinations of the cardiac conduction system and a coronary chemoreceptor from the hearts of two black males who had sickled erythrocytes. There were abundant foci of old and recent degeneration in the sinus node, atrioventricular node, and His bundle, as well as the coronary chemoreceptor. Many capillaries and small arteries were packed with sickled erythrocytes, among which small groups of aggregated platelets were also present. Focal fibromuscular dysplasia caused moderate to severe narrowing of many small coronary arteries, including those supplying the conduction system and chemoreceptor. These abnormalities are suggestive of electrical instability of the heart as at least one component of the lethal terminal events in some individuals with sickled erythrocytes. Both the foci of fibrosis and the focal fibromuscular dysplasia of small coronary arteries cannot be simply terminal or recent events but more likely take months or years in developing. For individuals with sickled erythrocytes, as in other examples of sudden death, there is a major element of chance concurrence of numerous otherwise independently less significant factors, but lethal cardiac electrical instability may be the final common pathway.

Quimiorreceptor orbitario en la rata: informe preliminar / Orbitary chemoreceptor in the rat preliminary report

Los quimiorreceptores son estructuras específicas ampliamente distribuidas en el organismo. El cuerpo carotídeo es el representante principal de este sistema, por lo que es el mejor estudiado y sirve de punto de comparación para el conocimiento de otros quimiorreceptores. El quimiorreceptor ciliar ha sido identificado únicamente en aves, pero su estructura no ha sido descrita en detalle. Este trabajo representa una breve comunicación preliminar.

Postmortem studies of the heart in three fatal cases of the eosinophilia-myalgia syndrome.

OBJECTIVE: To examine the hearts of individuals who died from the eosinophilia-myalgia syndrome associated with ingestion of L-tryptophan, with particular attention paid to the coronary arteries, the neural structures, and the conduction system of the heart because of reported terminal disturbances of cardiac rhythm and conduction. STUDY MATERIAL: Three hearts fixed in neutral formalin and well preserved with all the relevant areas of conduction system intact. METHODS: Light microscopic examination of subserial sections of the sinus node, atrioventricular node and His bundle, coronary chemoreceptor and regional nerves, ganglia, and small coronary arteries. Routine stains used were Goldner trichrome and Verhoeff-van Gieson. RESULTS: Arterial abnormalities were numerous and primarily of two types: focal fibromuscular dysplasia causing moderate to severe narrowing, as well as endarteritis and panarteritis. Extensive examples of neuritis and ganglionitis were present throughout the heart, including the conduction system, where arterial abnormalities were also abundant. In the coronary chemoreceptor there were both old and new lesions comprising focal inflammation with degeneration as well as older areas of fibrotic destruction. Within the sinus node, areas of dense fibrosis replaced all nodal tissue. These abnormalities were similar in nature and extent in all three hearts. CONCLUSIONS: The pathologic lesions present in the coronary arteries, neural structures, and conduction system of the heart in patients who died from the eosinophilia-myalgia syndrome provide a suitable anatomic substrate for substantial cardiac electrical instability, including the occurrence of sudden death. In cases of unexplained cardiac electrical instability or sudden unexpected death an inquiry should be made about previous use of L-tryptophan. In patients with the eosinophilia-myalgia syndrome, the possibility of cardiac electrical instability should be considered as part of long-range clinical management.

Carotid body hyperplasia in cystic fibrosis and cyanotic heart disease. A combined morphometric, ultrastructural, and biochemical study.

A combined morphometric, ultrastructural, and biochemical study was done on carotid bodies (CBs) obtained at autopsy from 213 patients in a pediatric and young adult population. The objective was to determine whether this group had statistically significant differences in sudden infant death syndrome (SIDS, n = 38), cystic fibrosis (CF, n = 30) and cyanotic heart disease (CHD, n = 17), compared with an age-matched control population (n = 128). Average combined weights of CBs in CF and CHD were significantly greater than those of controls in most age intervals (Student t test, P less than 0.05), and computerized planimetry showed an increase in both total surface area and area of "functional" parenchyma. There was diminished chief cell argyrophilia in 72% of CF CBs, and in 8 cases studied ultrastructurally there was moderate to marked depletion of dense-core neurosecretory granules. Most CBs from patients with CHD showed intense cytoplasmic argyrophilia similar to that of controls. Quantitative analysis for tissue catecholamines showed that dopamine was present in greatest concentration in each group of patients but was significantly elevated in CHD. There were no significant differences in morphometry, ultrastructure, or catecholamine content of CBs from SIDS victims, compared with age-related controls. These data add further support to CBs having a chemoreceptor role in humans with compensatory hypertrophy and hyperplasia occurring in most patients with chronic hypoxia due to CF and CHD. There were no significant findings to indicate that CBs play a direct role in the etiopathogenesis of SIDS.

Lung endocrine tumours.

The structure of bronchial carcinoids, oat cell carcinomas and pulmonary 'tumourlets' is described and evidence presented that they are related histogenetically, all being derived from certain specialized cells of endocrine or chemoreceptor nature found within the lining epithelium of the airways. Chemoreceptors related to pulmonary blood vessels have also been identified and two different types of pulmonary tumour have both been termed chemodectoma in the belief that they arise from such structures: these are the so-called multiple minute chemodectoma and the larger solitary variety but the exact histogenesis of both these tumours must remain conjectural at present.

Cross-circulation studies on the influence of hypoxia and hypoxaemia on neuro-epithelial bodies in young rabbits.

The reactions of the previously described neuro-epithelial bodies (NEB)(Lauweryns et al., 1969, 1970, 1972a, b, 1973a, b, c 1974, 1975) in young rabbits to: (1) hypoxia with normoxaemia in the arteria pulmonalis on the one hand, and (2) hypoxaemia in the arteria pulmonalis with normoxic aeration on the other hand, has been investigated by means of cross-circulation experiments and light microscopical, electron microscopical and morphometrical techniques. Hypoxically aerated young rabbits, which received normoxaemic blood in their arteria pulmonalis from a donor rabbit by means of an arterio-arterial cross-circulation with mutal exchange transfusion, revealed an increased exocytosis of the dense-core vesicles of their NEB. Normoxically aerated young rabbits which received hypoxaemic blood in an identical manner, did not exhibit an increased exocytosis. It is concluded that the NEB apparently react directly to the hypoxia of the inhaled air and not to the hypoxaemia of the pulmonary blood. By the release of serotonin and a polypeptide substance, they may produce a local vasoconstriction in hypoxically aerated lung areas, enabling an intrapulmonary regulation of the V/Q ratio. This is regarded as additional proof that the NEB--while being modulated by the CNS--probably are intrapulmonary chemoreceptors with local secretory activities, reacting to the composition of the inhaled air.

Chemodectoma of the orbit.

The histological and clinical features of a primary chemodectoma arising in the orbit are described. It is suggested that the tumour may have arisen from chemoreceptor tissue in the area of the lacrimal gland.