The neuroprotective steroid progesterone promotes mitochondrial uncoupling, reduces cytosolic calcium and augments stress resistance in yeast cells

Noscapine alleviates cerebral damage in ischemia-reperfusion injury in rats

With high unmet medical needs, stroke remains an intensely focused research area. Although noscapine is a neuroprotective agent, its mechanism of action in ischemic-reperfusion (I-R) injury is yet to be ascertained. We investigated the effect of noscapine on the molecular mechanisms of cell damage using yeast, and its neuroprotection on cerebral I-R injury in rats. Yeast, both wild-type and Δtrx2 strains, was evaluated for cell growth and viability, and oxidative stress to assess the noscapine effect at 8, 10, 12, and 20 μg/ml concentrations. The neuroprotective activity of noscapine (5 and 10 mg/kg; po for 8 days) was investigated in rats using middle cerebral artery occlusion-induced I-R injury. Infarct volume, neurological deficit, oxidative stress, myeloperoxidase activity, and histological alterations were determined in I-R rats. In vitro yeast assays exhibited significant antioxidant activity and enhanced cell tolerance against oxidative stress after noscapine treatment. Similarly, noscapine pretreatment significantly reduced infarct volume and edema in the brain. The neurological deficit was decreased and oxidative stress biomarkers, superoxide dismutase activity and glutathione levels, were significantly increased while lipid peroxidation showed significant decrease in comparison to vehicle-treated I-R rats. Myeloperoxidase activity, an indicator of inflammation, was also reduced significantly in treated rats; histological changes were attenuated with noscapine. The study demonstrates the protective effect of noscapine in yeast and I-R rats by improving cell viability and attenuating neuronal damage, respectively. This protective activity of noscapine could be attributed to potent free radical scavenging and inhibition of inflammation in cerebral ischemia-reperfusion injury.

Traumatic stress history interacts with sex and chronic peripheral inflammation to alter mitochondrial function of synaptosomes

BACKGROUND

Repeated exposures to chronic stress can lead to long lasting negative behavioral and metabolic outcomes. Here, we aim to determine the impact of chronic stress and chronic low-level inflammation on behavior and synaptosomal metabolism.

METHODS

Male (n = 31) and female (n = 32) C57Bl/6 mice underwent chronic repeated predation stress or daily handling for two rounds of 15 consecutive days of exposure during the adolescent and early adult timeframes. Subsequently, mice were exposed to repeated lipopolysaccharide (LPS; 7.5 × 10⁵ EU/kg) or saline injections every third day for eight weeks. Exploratory and social behaviors were assessed in the open field and social interaction tests prior to examination of learning and memory with the Barnes Maze. Mitochondrial function and morphology were assessed in synaptosomes post-mortem using the Cell Mito Stress test and Seahorse XFe24 analyzer, TEM, and western analysis, respectively. In addition, expression of TNF-α, IL-1ß, and ROMO1 were examined in the hippocampus and prefrontal cortex with Taqman qPCR. Circulating pro- and anti-inflammatory cytokines in the periphery were assessed using the MSD V-plex Proinflammatory Panel 1 following the first and last LPS injection as well as at the time of tissue collection. Circulating ROMO1 was assessed in terminal samples via ELISA.

RESULTS

Exposure to repeated predatory stress increased time spent in the corners of the open field, suggestive of anxiety-like behavior, in both males and females. There were no significant group differences in the social interaction test and minimal effects were evident in the Barnes maze. A history of chronic stress interacted with chronic LPS in male mice to lead to a deficit in synaptosomal respiration. Female mice were more sensitive to both chronic stress and chronic LPS such that either a history of chronic stress or chronic LPS exposure was sufficient to disrupt synaptosomal respiration in females. Both stress and chronic LPS were sufficient to increase inflammation and reactive oxygen in males centrally and peripherally. Females had increased markers of peripheral inflammation following acute LPS but no evidence of peripheral or central increases in inflammatory factors or reactive oxygen following chronic exposures.

CONCLUSION

Collectively, these data suggest that while metrics of inflammation and reactive oxygen are disrupted in males following chronic stress and chronic LPS, only the combined condition is sufficient to alter synaptosomal respiration. Conversely, although evidence of chronic inflammation or chronic elevation in reactive oxygen is absent, females demonstrate profound shifts in synaptosomal mitochondrial function with either a history of chronic stress or a history of chronic inflammation. These data highlight that different mechanisms are likely in play between the sexes and that sex differences in neural outcomes may be precipitated by sex-specific effects of life experiences on mitochondrial function in the synapse.

Correcting an instance of synthetic lethality with a pro-survival sequence

A human cDNA encoding the LIM domain containing 194 amino acid cysteine and glycine rich protein 3 (CSRP3) was identified as a BAX suppressor in yeast and a pro-survival sequence that abrogated copper mediated regulated cell death (RCD). Yeast lacks a CSRP3 orthologue but it has four LIM sequences, namely RGA1, RGA2, LRG1 and PXL1. These are known regulators of stress responses yet their roles in RCD remain unknown. Given that LIMs interact with other LIMs, we ruled out the possibility that overexpressed yeast LIMs alone could prevent RCD and that CSRP3 functions by acting as a dominant regulator of yeast LIMs. Of interest was the discovery that even though yeast cells lacking the LIM encoding PXL1 had no overt growth defect, it was nevertheless supersensitive to the effects of sublethal levels of copper. Heterologous expression of human CSPR3 as well as the pro-survival 14-3-3 sequence corrected this copper supersensitivity. These results show that the pxl1∆-copper synthetic lethality is likely due to the induction of RCD. This differs from the prevailing model in which synthetic lethality occurs because of specific defects generated by the combined loss of two overlapping but non-essential functions.

Progesterone receptor-mediated actions and the treatment of central nervous system disorders: An up-date of the known and the challenge of the unknown

Progesterone has been shown to exert a wide range of remarkable protective actions in experimental models of central nervous system injury or disease. However, the intimate mechanisms involved in each of these beneficial effects are not fully depicted. In this review, we intend to give the readers a thorough revision on what is known about the participation of diverse receptors and signaling pathways in progesterone-mediated neuroprotective, pro-myelinating and anti-inflammatory outcomes, as well as point out to novel regulatory mechanisms that could open new perspectives in steroid-based therapies.

Distribution of and steroid hormone effects on calbindin-D9k in the immature rat brain

Calbindin-D_9k (CaBP-9k), one of the major calcium-binding and calcium-buffering proteins, is important in the physiological functioning of organs. The neuroanatomical localization of CaBP-9k in the rodent brain has not been reported; thus, this study investigated the neuroanatomical distribution of CaBP-9k and the regulation of CaBP-9k expression on steroid hormones in the immature rat brain. To confirm the influence of steroid hormones on CaBP-9k expression, immature female rats were injected for 5 days with estrogen (E2), progesterone (P4), dexamethasone (DEX), and their antagonists (ICI 182, 780 and RU 486). The localization and expression of the CaBP-9k protein in brain regions were identified by immunofluorescence and western blot assays, respectively. We observed that CaBP-9k expression was especially strong in hypothalamus, cerebellum, and brain stem. In addition, CaBP-9k was colocalized with mature-, GABAergic, dopaminergic, and oxytocinergic neurons. We also observed that the CaBP-9k protein level was significantly increased by P4 and reversed by antagonist RU 486 treatment in immature rat brain. In summary, CaBP-9k positive cells have a wide distribution in the immature rat brain, and CaBP-9k expression is regulated by P4. We suggest that CaBP-9k expression regulated by steroid hormone may serve as an important regulator of cytosolic calcium concentration in the brain.

Studying Huntington's Disease in Yeast: From Mechanisms to Pharmacological Approaches

Huntington's disease (HD) is a neurodegenerative disorder that leads to progressive neuronal loss, provoking impaired motor control, cognitive decline, and dementia. So far, HD remains incurable, and available drugs are effective only for symptomatic management. HD is caused by a mutant form of the huntingtin protein, which harbors an elongated polyglutamine domain and is highly prone to aggregation. However, many aspects underlying the cytotoxicity of mutant huntingtin (mHTT) remain elusive, hindering the efficient development of applicable interventions to counteract HD. An important strategy to obtain molecular insights into human disorders in general is the use of eukaryotic model organisms, which are easy to genetically manipulate and display a high degree of conservation regarding disease-relevant cellular processes. The budding yeast Saccharomyces cerevisiae has a long-standing and successful history in modeling a plethora of human maladies and has recently emerged as an effective tool to study neurodegenerative disorders, including HD. Here, we summarize some of the most important contributions of yeast to HD research, specifically concerning the elucidation of mechanistic features of mHTT cytotoxicity and the potential of yeast as a platform to screen for pharmacological agents against HD.

Guidelines and recommendations on yeast cell death nomenclature

Elucidating the biology of yeast in its full complexity has major implications for science, medicine and industry. One of the most critical processes determining yeast life and physiology is cel-lular demise. However, the investigation of yeast cell death is a relatively young field, and a widely accepted set of concepts and terms is still missing. Here, we propose unified criteria for the defi-nition of accidental, regulated, and programmed forms of cell death in yeast based on a series of morphological and biochemical criteria. Specifically, we provide consensus guidelines on the differ-ential definition of terms including apoptosis, regulated necrosis, and autophagic cell death, as we refer to additional cell death rou-tines that are relevant for the biology of (at least some species of) yeast. As this area of investigation advances rapidly, changes and extensions to this set of recommendations will be implemented in the years to come. Nonetheless, we strongly encourage the au-thors, reviewers and editors of scientific articles to adopt these collective standards in order to establish an accurate framework for yeast cell death research and, ultimately, to accelerate the pro-gress of this vibrant field of research.

Role of Sex Hormones on Brain Mitochondrial Function, with Special Reference to Aging and Neurodegenerative Diseases

The mitochondria have a fundamental role in both cellular energy supply and oxidative stress regulation and are target of the effects of sex steroids, particularly the neuroprotective ones. Aging is associated with a decline in the levels of different steroid hormones, and this decrease may underline some neural dysfunctions. Besides, modifications in mitochondrial functions associated with aging processes are also well documented. In this review, we will discuss studies that describe the modifications of brain mitochondrial function and of steroid levels associated with physiological aging and with neurodegenerative diseases. A special emphasis will be placed on describing and discussing our recent findings concerning the concomitant study of mitochondrial function (oxidative phosphorylation, oxidative stress) and brain steroid levels in both young (3-month-old) and aged (20-month-old) male and female mice.

Steroid and Xenobiotic Receptor Signalling in Apoptosis and Autophagy of the Nervous System

Apoptosis and autophagy are involved in neural development and in the response of the nervous system to a variety of insults. Apoptosis is responsible for cell elimination, whereas autophagy can eliminate the cells or keep them alive, even in conditions lacking trophic factors. Therefore, both processes may function synergistically or antagonistically. Steroid and xenobiotic receptors are regulators of apoptosis and autophagy; however, their actions in various pathologies are complex. In general, the estrogen (ER), progesterone (PR), and mineralocorticoid (MR) receptors mediate anti-apoptotic signalling, whereas the androgen (AR) and glucocorticoid (GR) receptors participate in pro-apoptotic pathways. ER-mediated neuroprotection is attributed to estrogen and selective ER modulators in apoptosis- and autophagy-related neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases, stroke, multiple sclerosis, and retinopathies. PR activation appeared particularly effective in treating traumatic brain and spinal cord injuries and ischemic stroke. Except for in the retina, activated GR is engaged in neuronal cell death, whereas MR signalling appeared to be associated with neuroprotection. In addition to steroid receptors, the aryl hydrocarbon receptor (AHR) mediates the induction and propagation of apoptosis, whereas the peroxisome proliferator-activated receptors (PPARs) inhibit this programmed cell death. Most of the retinoid X receptor-related xenobiotic receptors stimulate apoptotic processes that accompany neural pathologies. Among the possible therapeutic strategies based on targeting apoptosis via steroid and xenobiotic receptors, the most promising are the selective modulators of the ER, AR, AHR, PPARγ agonists, flavonoids, and miRNAs. The prospective therapies to overcome neuronal cell death by targeting autophagy via steroid and xenobiotic receptors are much less recognized.