Functional ectopic neural lobe increases GAP-43 expression via PI3K/AKT pathways to alleviate central diabetes insipidus after pituitary stalk lesion in rats

Oxytocin attenuates hypothalamic injury-induced cognitive dysfunction by inhibiting hippocampal ERK signaling and Aβ deposition

In clinical settings, tumor compression, trauma, surgical injury, and other types of injury can cause hypothalamic damage, resulting in various types of hypothalamic dysfunction. Impaired release of oxytocin can lead to cognitive impairment and affect prognosis and long-term quality of life after hypothalamic injury. Hypothalamic injury-induced cognitive dysfunction was detected in male animals. Behavioral parameters were measured to assess the characteristics of cognitive dysfunction induced by hypothalamic-pituitary stalk lesions. Brains were collected for high-throughput RNA sequencing and immunostaining to identify pathophysiological changes in hippocampal regions highly associated with cognitive function after injury to corresponding hypothalamic areas. Through transcriptomic analysis, we confirmed the loss of oxytocin neurons after hypothalamic injury and the reversal of hypothalamic-induced cognitive dysfunction after oxytocin supplementation. Furthermore, overactivation of the ERK signaling pathway and β-amyloid deposition in the hippocampal region after hypothalamic injury were observed, and cognitive function was restored after inhibition of ERK signaling pathway overactivation. Our findings suggest that cognitive dysfunction after hypothalamic injury may be caused by ERK hyperphosphorylation in the hippocampal region resulting from a decrease in the number of oxytocin neurons, which in turn causes β-amyloid deposition.

Alternating current stimulation promotes neurite outgrowth and plasticity in neurons through activation of the PI3K/AKT signaling pathway

As a commonly used physical intervention, electrical stimulation (ES) has been demonstrated to be effective in the treatment of central nervous system disorders. Currently, researchers are studying the effects of electrical stimulation on individual neurons and neural networks, which are dependent on factors such as stimulation intensity, duration, location, and neuronal properties. However, the exact mechanism of action of electrical stimulation remains unclear. In some cases, repeated or prolonged electrical stimulation can lead to changes in the morphology or function of the neuron. In this study, immunofluorescence staining and Sholl analysis are used to assess changes in the neurite number and axon length to determine the optimal pattern and stimulation parameters of ES for neurons. Neuronal death and plasticity are detected by TUNEL staining and microelectrode array assays, respectively. mRNA sequencing and bioinformatics analysis are applied to predict the key targets of the action of ES on neurons, and the identified targets are validated by western blot analysis and qRT-PCR. The effects of alternating current stimulation (ACS) on neurons are more significant than those of direct current stimulation (DCS), and the optimal parameters are 3 μA and 20 min. ACS stimulation significantly increases the number of neurites, the length of axons and the spontaneous electrical activity of neurons, significantly elevates the expression of growth-associated protein-43 (GAP-43) without significant changes in the expression of neurotrophic factors. Furthermore, application of PI3K/AKT-specific inhibitors significantly abolishes the beneficial effects of ACS on neurons, confirming that the PI3K/AKT pathway is an important potential signaling pathway in the action of ACS.

Vasopressin as Possible Treatment Option in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is rather common, presenting with prevalent early problems in social communication and accompanied by repetitive behavior. As vasopressin was implicated not only in salt-water homeostasis and stress-axis regulation, but also in social behavior, its role in the development of ASD might be suggested. In this review, we summarized a wide range of problems associated with ASD to which vasopressin might contribute, from social skills to communication, motor function problems, autonomous nervous system alterations as well as sleep disturbances, and altered sensory information processing. Beside functional connections between vasopressin and ASD, we draw attention to the anatomical background, highlighting several brain areas, including the paraventricular nucleus of the hypothalamus, medial preoptic area, lateral septum, bed nucleus of stria terminalis, amygdala, hippocampus, olfactory bulb and even the cerebellum, either producing vasopressin or containing vasopressinergic receptors (presumably V1a). Sex differences in the vasopressinergic system might underline the male prevalence of ASD. Moreover, vasopressin might contribute to the effectiveness of available off-label therapies as well as serve as a possible target for intervention. In this sense, vasopressin, but paradoxically also V1a receptor antagonist, were found to be effective in some clinical trials. We concluded that although vasopressin might be an effective candidate for ASD treatment, we might assume that only a subgroup (e.g., with stress-axis disturbances), a certain sex (most probably males) and a certain brain area (targeting by means of virus vectors) would benefit from this therapy.

A procedure in mice to obtain intact pituitary-infundibulum-hypothalamus preparations: a method to evaluate the reconstruction of hypothalamohypophyseal system

PURPOSE

The histopathological study of brain tissue is a common method in neuroscience. However, efficient procedures to preserve the intact hypothalamic-pituitary brain specimens are not available in mice for histopathological study.

METHOD

We describe a detailed procedure for obtaining mouse brain with pituitary-hypothalamus continuity. Unlike the traditional methods, we collect the brain via a ventral approach. We cut the intraoccipital synchondrosis, transection the endocranium of pituitary, broke the spheno-occipital synchondrosis, expose the posterior edge of pituitary, separate the trigeminal nerve, then the intact pituitary gland was preserved.

RESULT

We report an more effective and practical method to obtain continuous hypothalamus -pituitary preparations based on the preserve of leptomeninges.

COMPARED WITH THE EXISTING METHODS

Our procedure effectively protects the integrity of the fragile infundibulum preventing the pituitary from separating from the hypothalamus. This procedure is more convenient and efficient.

CONCLUSION

We present a convenient and practical procedure to obtain intact hypothalamic-pituitary brain specimens for subsequent histopathological evaluation in mice.

Microglial infiltration mediates cognitive dysfunction in rat models of hypothalamic obesity via a hypothalamic-hippocampal circuit involving the lateral hypothalamic area

This study aimed to explore the mechanism underlying cognitive dysfunction mediated by the lateral hypothalamic area (LHA) in a hypothalamic-hippocampal circuit in rats with lesion-induced hypothalamic obesity (HO). The HO model was established by electrically lesioning the hypothalamic nuclei. The open field (OP) test, Morris water maze (MWM), novel object recognition (NOR), and novel object location memory (NLM) tests were used to evaluate changes in cognition due to alterations in the hypothalamic-hippocampal circuit. Western blotting, immunohistochemical staining, and cholera toxin subunit B conjugated with Alexa Fluor 488 (CTB488) reverse tracer technology were used to determine synaptophysin (SYN), postsynaptic density protein 95 (PSD95), ionized calcium binding adaptor molecule 1 (Iba1), neuronal nuclear protein (NeuN), and Caspase3 expression levels and the hypothalamic-hippocampal circuit. In HO rats, severe obesity was associated with cognitive dysfunction after the lesion of the hypothalamus. Furthermore, neuronal apoptosis and activated microglia in the downstream of the lesion area (the LHA) induced microglial infiltration into the intact hippocampus via the LHA-hippocampal circuit, and the synapses engulfment in the hippocampus may be the underlying mechanism by which the remodeled microglial mediates memory impairments in HO rats. The HO rats exhibited microglial infiltration and synapse loss into the hippocampus from the lesioned LHA via the hypothalamic-hippocampal circuit. The underlying mechanisms of memory function may be related to the circuit.

Adult neurogenesis of the median eminence contributes to structural reconstruction and recovery of body fluid metabolism in hypothalamic self-repair after pituitary stalk lesion

Body fluid homeostasis is critical to survival. The integrity of the hypothalamo-neurohypophysial system (HNS) is an important basis of the precise regulation of body fluid metabolism and arginine vasopressin (AVP) hormone release. Clinically, some patients with central diabetes insipidus (CDI) due to HNS lesions can experience recovery compensation of body fluid metabolism. However, whether the hypothalamus has the potential for structural plasticity and self-repair under pathological conditions remains unclear. Here, we report the repair and reconstruction of a new neurohypophysis-like structure in the hypothalamic median eminence (ME) after pituitary stalk electrical lesion (PEL). We show that activated and proliferating adult neural progenitor cells differentiate into new mature neurons, which then integrate with remodeled AVP fibers to reconstruct the local AVP hormone release neural circuit in the ME after PEL. We found that the transcription factor of NK2 homeobox 1 (NKX2.1) and the sonic hedgehog signaling pathway, mediated by NKX2.1, are the key regulators of adult hypothalamic neurogenesis. Taken together, our study provides evidence that adult ME neurogenesis is involved in the structural reconstruction of the AVP release circuit and eventually restores body fluid metabolic homeostasis during hypothalamic self-repair.

Nomograms to Predict Endocrinological Deficiency in Patients With Surgically Treated Craniopharyngioma

Objective

Postoperative hypopituitarism associated with increased risks of premature mobility and mortality is often encountered in craniopharyngioma patients. The aim of our study is to construct nomograms related to injury types of the hypothalamus-pituitary axis (HPA) to predict hypopituitarism 1 year after surgery.

Methods

Craniopharyngioma patients undergoing initial endoscopic endonasal surgery between December 2012 and March 2021 in our center were retrospectively reviewed, and injury types of the HPA were categorized according to intraoperative endoscopic observation. Included patients were randomly divided into a training group and a validation group. Nomograms were established based on the results of multivariate logistic analysis. The predictive performance of the nomograms was evaluated in the training and validation groups.

Results

A total of 183 patients with craniopharyngioma were enrolled, and seven injury types of the HPA were summarized. Relative to intact HPA, exclusive hypothalamus injury significantly increased the risk of anterior (OR, 194.174; 95% CI, 21.311-1769.253; p < 0.001) and posterior pituitary dysfunction (OR, 31.393; 95% CI, 6.319-155.964; p < 0.001) 1 year after surgery, while exclusively sacrificing stalk infiltrated by tumors did not significantly increase the risk of anterior (OR, 5.633; 95% CI, 0.753-42.133; p = 0.092) and posterior pituitary dysfunction (OR, 1.580; 95% CI, 0.257-9.707; p = 0.621) 1 year after surgery. In the training group, the AUCs of nomograms predicting anterior and posterior pituitary dysfunction 1 year after surgery were 0.921 and 0.885, respectively, compared with 0.921 and 0.880 in the validation group.

Conclusions

Intact hypothalamus structure is critical in maintaining pituitary function. Moreover, our preliminary study suggests that the pituitary stalk infiltrated by craniopharyngioma could be sacrificed to achieve radical resection, without substantially rendering significantly worse endocrinological efficiency 1 year after surgery. The user-friendly nomograms can be used to predict hypopituitarism 1 year after surgery.

An Efficient Method for the Isolation and Cultivation of Hypothalamic Neural Stem/Progenitor Cells From Mouse Embryos

The hypothalamus is the key region that regulates the neuroendocrine system as well as instinct behaviors, and hypothalamic dysfunction causes refractory clinical problems. Recent studies have indicated that neural stem/progenitor cell (NSPC) in the hypothalamus play a crucial role in hypothalamic function. However, specific hypothalamic NSPC culture methods have not been established, especially not detailed or efficient surgical procedures. The present study presented a convenient, detailed and efficient method for the isolation and cultivation of hypothalamic NSPCs from embryonic day 12.5 mice. The procedure includes embryo acquisition, brain microdissection to quickly obtain hypothalamic tissue and hypothalamic NSPC culture. Hypothalamic NSPCs can be quickly harvested and grow well in both neurosphere and adherent cultures through this method. Additionally, we confirmed the cell origin and evaluated the proliferation and differentiation properties of cultured cells. In conclusion, we present a convenient and practical method for the isolation and cultivation of hypothalamic NSPCs that can be used in extensive hypothalamic studies.

Transcriptomic Analysis Reveals that Activating Transcription Factor 3/c-Jun/Lgals3 Axis Is Associated with Central Diabetes Insipidus after Hypothalamic Injury

BACKGROUND

Hypothalamic injury causes several complicated neuroendocrine-associated disorders, such as water-electrolyte imbalance, obesity, and hypopituitarism. Among these, central diabetes insipidus (CDI), characterized by polyuria, polydipsia, low urine specific gravity, and deficiency of arginine vasopressin contents, is a typical complication after hypothalamic injury.

METHODS

CDI was induced by hypothalamic pituitary stalk injury in male animals. Behavioral parameters and blood sample were collected to evaluate the characteristics of body fluid metabolism imbalance. The brains were harvested for high-throughput RNA sequencing and immunostaining to identify pathophysiological changes in corresponding hypothalamic nuclei.

RESULTS

Based on transcriptomic analysis, we demonstrated the upregulation of the activating transcription factor 3 (Atf3)/c-Jun axis and identified Lgals3, a microglial activation-related gene, as the most significant target gene in response to the body fluid imbalance in CDI. Furthermore, we found that the microglia possessed elevated phagocytic ability, which could promote the elimination of arginine vasopressin neurons after hypothalamic injury.

CONCLUSION

Our findings suggested that the Atf3/c-Jun/Lgals3 axis was associated with the microglial activation, and might participate in the loss of functional arginine vasopressin neurons in CDI after hypothalamic injury.

ACQUIRED ECTOPIC POSTERIOR PITUITARY BRIGHT SPOT DUE TO VASCULOTOXIC SNAKEBITE

OBJECTIVE

Vasculotoxic envenomation is an uncommon cause of hypopituitarism. Most described cases have varying extent of anterior pituitary dysfunction, but posterior pituitary involvement is extremely rare.

METHODS

Clinical, biochemical, and radiologic evaluation of a young female who presented with secondary amenorrhea was performed. A brief literature review of envenomation-induced hypopituitarism is included.

RESULTS

A 26-year-old female presented with secondary amenorrhea since the age of 20 years. She had normal stature. Her past medical history was significant for a vasculotoxic snakebite 12 years back requiring hemodialysis, but no hormonal testing was done at that time. Current evaluation showed anterior hypopituitarism. An insulin-induced hypoglycemia test confirmed deficiencies of cortisol and growth hormone axes (peak values 348 nmol/L and 0.03 ng/mL). There was no diabetes insipidus. Magnetic resonance imaging revealed a hypoplastic anterior pituitary with an ectopic posterior pituitary. In view of normal stature and secondary amenorrhea, a diagnosis of envenomation-induced hypopituitarism with ectopic posterior pituitary (EPP) was made. A brief literature review of envenomation-induced hypopituitarism showed both acute and delayed presentation, male predominance, and variable lag period (weeks to years). Nearly half of all patients were asymptomatic. The most common axis involved in acute presentation was the cortisol axis, whereas the thyroid and gonadotroph axes were commonly involved in delayed hypopituitarism.

CONCLUSION

Vasculotoxic envenomation is a rare cause of acquired hypopituitarism. EPP in the index case was probably due to the "axonal dieback" phenomenon and subsequent regeneration of the axons at a more caudal site. This case, being the first instance of acquired EPP following envenomation, expands the spectrum of envenomation-induced hypopituitarism.

A retaining sphenoid and dura procedure in the rat to obtain intact pituitary-infundibulum-hypothalamus preparations

BACKGROUND

The histopathological study of brain tissue is a conventional method in neuroscience. However, procedures specifically developed to recover intact hypothalamic-pituitary brain specimens, are not available.

NEW METHOD

We describe a detailed protocol for obtaining intact rat brain with pituitary-hypothalamus continuity through an intact infundibulum. The brain is collected via a ventral approach through removing the skull base. Membranous structures surrounding the hypothalamus-pituitary system can be preserved, including vasculature.

RESULTS

We report a retaining sphenoid and dura technique to obtain intact hypothalamic-pituitary brain preparations, and we confirm the practicability of this method. By combination of this technique with histological analysis or 3D brain tissue clearing and imaging methods, the functional morphology structure of the hypothalamus-pituitary can be further explored.

COMPARISON WITH EXISTING METHOD

The current procedure is limited in showing the connection between the hypothalamus and the pituitary. Our procedure effectively protects the integrity of the fragile infundibulum and thus prevents the pituitary from separating from the hypothalamus.

CONCLUSIONS

We present a convenient and practical approach to obtain intact hypothalamus-pituitary brain specimens for subsequent histopathological evaluation.

[JNK/c-Jun signaling pathway mediates arginine vasopressin neuron regeneration by promoting cytoskeleton reconstruction in rats with electrical lesions of the pituitary stalk]

OBJECTIVE

To investigate the mechanism by which doublecortin promotes the recovery of cytoskeleton in arginine vasopressin (AVP) neurons in rats with electrical lesions of the pituitary stalk (PEL).

METHODS

Thirty-two SD rats were randomized into PEL group with electrical lesions of the pituitary stalk through the floor of the skull base (n=25) and sham operation group (n=7), and the daily water consumption (DWC), daily urine volume (DUV) and urine specific gravity (USG) of the rats were recorded. Four rats on day 1 and 7 rats on each of days 3, 7 and 14 after PEL as well as the sham-operated rats were sacrificed for detection of the expressions of β-Tubulin (Tuj1), doublecortin and caspase- 3 in the AVP neurons of the supraoptic nucleus using immunofluorescence assay and Western blotting.

RESULTS

After PEL, the rats exhibited a typical triphasic pattern of diabetes insipidus, with the postoperative days 1-2 as the phase one, days 3-5 as the phase two, and days 6-14 as the phase three. Immunofluorescent results indicated the repair of the AVP neurons evidenced by significantly increased doublecortin expressions in the AVP neurons following PEL; similarly, the expression of Tuj1 also increased progressively after PEL, reaching the peak level on day 7 after PEL. The apoptotic rates of the AVP neurons exhibited a reverse pattern of variation, peaking on postoperative day 3 followed by progressive reduction till day 14. Western blotting showed that the expressions of c-Jun and p-c-Jun were up-regulated significantly on day 3 (P < 0.05) and 7 (P < 0.01) after PEL, while an upregulated p-JNK expression was detected only on day 3 (P < 0.05), as was consistent with the time-courses of neuronal recovery and apoptosis after PEL.

CONCLUSIONS

JNK/c-Jun pathway is activated after PEL to induce apoptosis of AVP neurons in the acute phase and to promote the repair of neuronal cytoskeleton by up-regulation of doublecortin and Tuj1 expressions.

Endoplasmic reticulum stress induces apoptosis of arginine vasopressin neurons in central diabetes insipidus via PI3K/Akt pathway

Aims

Central diabetes insipidus (CDI), a typical complication caused by pituitary stalk injury, often occurs after surgery, trauma, or tumor compression around hypothalamic structures such as the pituitary stalk and optic chiasma. CDI is linked to decreased arginine vasopressin (AVP) neurons in the hypothalamic supraoptic nucleus and paraventricular nucleus, along with a deficit in circulating AVP and oxytocin. However, little has been elucidated about the changes in AVP neurons in CDI. Hence, our study was designed to understand the role of several pathophysiologic changes such as endoplasmic reticulum (ER) stress and apoptosis of AVP neurons in CDI.

Methods

In a novel pituitary stalk electric lesion (PEL) model to mimic CDI, immunofluorescence and immunoblotting were used to understand the underlying regulatory mechanisms.

Results

We reported that in CDI condition, generated by PEL, ER stress induced apoptosis of AVP neurons via activation of the PI3K/Akt and ERK pathways. Furthermore, application of N‐acetylcysteine protected hypothalamic AVP neurons from ER stress‐induced apoptosis through blocking the PI3K/Akt and ERK pathways.

Conclusion

Our findings showed that AVP neurons underwent apoptosis induced by ER stress, and ER stress might play a vital role in CDI condition through the PI3K/Akt and ERK pathways.