Effect of Zolpidem on nocturnal arousals and susceptibility to central sleep apnea.

PURPOSE: Arousals may contribute to the pathogenesis of sleep-disordered breathing (SDB) and central sleep apnea (CSA). We aimed to determine the effect of the nonbenzodiazepine hypnotic zolpidem on the frequency of respiratory-related arousals and central apnea in patients with moderate-to-severe SDB. We hypothesized that zolpidem decreases the severity of SDB by decreasing the frequency of respiratory-related arousals. METHODS: Patients with apnea-hypopnea index ≥ 15 events/hour and central apnea-hypopnea index ≥ 5 events/hour underwent a sleep study on zolpidem 5 mg and a sleep study with no medication in a randomized order. The respiratory arousal index was compared between the two studies using a randomized crossover design. Sleep, respiratory, and physiologic parameters, including the CO2 reserve and the respiratory arousal threshold, were also compared. RESULTS: Eleven participants completed the study. Compared to no treatment, zolpidem reduced the respiratory arousal index (39.7 ± 7.7 vs. 23.3 ± 4.4 events/h, P = 0.031). Zolpidem also lowered the total apnea-hypopnea index (55.6 ± 8.5 vs. 41.3 ± 7.5 events/hour, P = 0.033) but did not affect other clinical and physiologic parameters. Compared to control, zolpidem did not widen CO2 reserve (- 0.44 ± 1.47 vs. - 0.63 ± 0.86 mmHg, P = 0.81). The respiratory arousal threshold did not show a significant change on zolpidem compared to control (- 8.72 ± 2.1 vs. - 8.25 ± 2.81 cmH2O, P = 0.41). CONCLUSION: Nocturnal arousals and overall SDB severity were reduced with a single dose of zolpidem in patients with moderate-to-severe sleep-disordered breathing with increased susceptibility for central apnea. Zolpidem did not widen the CO2 reserve or increase the arousal threshold. TRIAL REGISTRATION: Clinicaltrials.gov. Sleep and Breathing in the General Population - Chemical Stimuli (NCT04720547).

Tetraplegia is associated with increased hypoxic ventilatory response during nonrapid eye movement sleep.

People with cervical spinal cord injury (SCI) are likely to experience chronic intermittent hypoxia while sleeping. The physiological effects of intermittent hypoxia on the respiratory system during spontaneous sleep in individuals with chronic cervical SCI are unknown. We hypothesized that individuals with cervical SCI would demonstrate higher short- and long-term ventilatory responses to acute intermittent hypoxia (AIH) exposure than individuals with thoracic SCI during sleep. Twenty participants (10 with cervical SCI [9 male] and 10 with thoracic SCI [6 male]) underwent an AIH and sham protocol during sleep. During the AIH protocol, each participant experienced 15 episodes of isocapnic hypoxia using mixed gases of 100% nitrogen (N2 ) and 40% carbon dioxide (CO2 ) to achieve an oxygen saturation of less than 90%. This was followed by two breaths of 100% oxygen (O2 ). Measurements were collected before, during, and 40 min after the AIH protocol to obtain ventilatory data. During the sham protocol, participants breathed room air for the same amount of time that elapsed during the AIH protocol and at approximately the same time of night. Hypoxic ventilatory response (HVR) during the AIH protocol was significantly higher in participants with cervical SCI than those with thoracic SCI. There was no significant difference in minute ventilation (V.E. ), tidal volume (V.T. ), or respiratory frequency (f) during the recovery period after AIH in cervical SCI compared to thoracic SCI groups. Individuals with cervical SCI demonstrated a significant short-term increase in HVR compared to thoracic SCI. However, there was no evidence of ventilatory long-term facilitation following AIH in either group.

Targeting autophagy, oxidative stress, and ER stress for neurodegenerative disease treatment.

Protein homeostasis is a vital process for cell function and, therefore, disruption of the molecular mechanisms involved in this process, such as autophagy, may contribute to neurodegenerative diseases (NDs). Apart from autophagy disruption, excess oxidative stress and endoplasmic reticulum (ER) stress are additional main molecular mechanisms underlying neurodegeneration, leading to protein aggregation, and mitochondrial dysfunction. Notably, these primary molecular processes are interconnected pathways, which have synergistic effects on each other. Therefore, we propose that targeting of the crosstalk between autophagy, oxidative stress and ER stress simultaneously may play a critical role in healing NDs. NeuroNanoTechnology, as a revolutionized approach, in combination with an in-silico strategy, holds great promise for developing de-novo structures for targeting and modulating neuro-molecular pathways. Accordingly, this review outlines the contributions of autophagy, oxidative stress, and ER stress in neurodegenerative conditions along with a particular focus on the crosstalk among these pathways. Furthermore, we provide a comprehensive discussion on the potential of nanomaterials to target this crosstalk and suggest this potential as a promising opportunity in neuroprotection.

Enhancing autophagy in Alzheimer's disease through drug repositioning.

Alzheimer's disease (AD) is one of the biggest human health threats due to increases in aging of the global population. Unfortunately, drugs for treating AD have been largely ineffective. Interestingly, downregulation of macroautophagy (autophagy) plays an essential role in AD pathogenesis. Therefore, targeting autophagy has drawn considerable attention as a therapeutic approach for the treatment of AD. However, developing new therapeutics is time-consuming and requires huge investments. One of the strategies currently under consideration for many diseases is "drug repositioning" or "drug repurposing". In this comprehensive review, we have provided an overview of the impact of autophagy on AD pathophysiology, reviewed the therapeutics that upregulate autophagy and are currently used in the treatment of other diseases, including cancers, and evaluated their repurposing as a possible treatment option for AD. In addition, we discussed the potential of applying nano-drug delivery to neurodegenerative diseases, such as AD, to overcome the challenge of crossing the blood brain barrier and specifically target molecules/pathways of interest with minimal side effects.

Autophagy: The Potential Link between SARS-CoV-2 and Cancer.

COVID-19 infection survivors suffer from a constellation of symptoms referred to as post-acute COVID-19 syndrome. However, in the wake of recent evidence highlighting the long-term persistence of SARS-CoV-2 antigens in tissues and emerging information regarding the interaction between SARS-CoV-2 proteins and various components of the host cell macroautophagy/autophagy machinery, the unforeseen long-term consequences of this infection, such as increased risk of malignancies, should be explored. Although SARS-CoV-2 is not considered an oncogenic virus, the possibility of increased risk of cancer among COVID-19 survivors cannot be ruled out. Herein, we provide an overview of the possible mechanisms leading to cancer development, particularly obesity-related cancers (e.g., colorectal cancer), resulting from defects in autophagy and the blockade of the autophagic flux, and also immune escape in COVID-19 survivors. We also highlight the potential long-term implications of COVID-19 infection in the prognosis of patients with cancer and their response to different cancer treatments. Finally, we consider future directions for further investigations on this matter.

Alzheimer's Disease Pathogenesis: Role of Autophagy and Mitophagy Focusing in Microglia.

Alzheimer's disease (AD) is a debilitating neurological disorder, and currently, there is no cure for it. Several pathologic alterations have been described in the brain of AD patients, but the ultimate causative mechanisms of AD are still elusive. The classic hallmarks of AD, including amyloid plaques (Aß) and tau tangles (tau), are the most studied features of AD. Unfortunately, all the efforts targeting these pathologies have failed to show the desired efficacy in AD patients so far. Neuroinflammation and impaired autophagy are two other main known pathologies in AD. It has been reported that these pathologies exist in AD brain long before the emergence of any clinical manifestation of AD. Microglia are the main inflammatory cells in the brain and are considered by many researchers as the next hope for finding a viable therapeutic target in AD. Interestingly, it appears that the autophagy and mitophagy are also changed in these cells in AD. Inside the cells, autophagy and inflammation interact in a bidirectional manner. In the current review, we briefly discussed an overview on autophagy and mitophagy in AD and then provided a comprehensive discussion on the role of these pathways in microglia and their involvement in AD pathogenesis.

Mutant Huntingtin stalls ribosomes and represses protein synthesis in a cellular model of Huntington disease.

The polyglutamine expansion of huntingtin (mHTT) causes Huntington disease (HD) and neurodegeneration, but the mechanisms remain unclear. Here, we found that mHtt promotes ribosome stalling and suppresses protein synthesis in mouse HD striatal neuronal cells. Depletion of mHtt enhances protein synthesis and increases the speed of ribosomal translocation, while mHtt directly inhibits protein synthesis in vitro. Fmrp, a known regulator of ribosome stalling, is upregulated in HD, but its depletion has no discernible effect on protein synthesis or ribosome stalling in HD cells. We found interactions of ribosomal proteins and translating ribosomes with mHtt. High-resolution global ribosome footprint profiling (Ribo-Seq) and mRNA-Seq indicates a widespread shift in ribosome occupancy toward the 5' and 3' end and unique single-codon pauses on selected mRNA targets in HD cells, compared to controls. Thus, mHtt impedes ribosomal translocation during translation elongation, a mechanistic defect that can be exploited for HD therapeutics.

Feasibility of a peer-led, manual wheelchair maintenance skills training programme to improve wheelchair efficiency, and knowledge and confidence about wheelchair maintenance: a pre-post study.

BACKGROUND: Wheelchair users typically receive little training about wheelchair maintenance. Therefore, we developed a peer-led, manual wheelchair skills maintenance training programme, with the intention of evaluating its efficacy in a future experimental study. PURPOSE: The purpose of this feasibility study was to examine how well we were able to implement the training programme and to evaluate the feasibility of conducting a larger scale clinical trial. SETTING: Spinal cord injury research centre. PARTICIPANTS: Five mentors and fifteen mentees were recruited to complete this feasibility study. METHOD: We collected information about recruitment capability and sample characteristics, data collection procedure, acceptability of the training programme, resources required, and participants' responses to the intervention. Participants completed all the items and we had little missing data. Participants did not face any difficulty answering the questionnaires or performing the tests. Therefore, we could conclude data collection was feasible moving forward to perform larger efficacy trials. The acceptability of the wheelchair maintenance programme was more than 90%. There was a statistically significant improvement in wheelchair maintenance knowledge test and total rolling resistance. Confidence of mentees increased significantly after the training. Improvements in the 3-cone test and the 6-min push test results were not significant. CONCLUSIONS: If recruitment and scheduling challenges can be overcome, our data suggested that it is feasible to conduct a larger experimental study to test the efficacy of the programme.Implications for RehabilitationWheelchair maintenance skills are important to help wheelchair users keep their wheelchairs working safely and efficiently.The findings from this study suggest that a peer-led wheelchair maintenance training programme may improve participants' wheelchair maintenance knowledge and maintenance self-confidence.The study also suggests that a peer-led wheelchair maintenance training programme may decrease the rolling resistance of participants' wheelchairs.A larger clinical trial is needed to demonstrate the efficacy of this intervention authoritatively.

Injuries Associated with Crutch Use: A Narrative Review.

Crutches are commonly prescribed in physiatric settings to help offload the lower extremities. Crutch use, however, results in abnormal and repetitive weight-bearing through the upper extremities that may result in secondary injury. This narrative review investigates injury types and risk factors associated with crutch use in order to guide healthcare providers on injury prevention strategies. Medline, EMBASE, CINAHL, and the Cochrane Library were systematically reviewed for publications between 1950 and 2018 on neurological, musculoskeletal, or vascular complications associated with crutch use. Titles and abstracts (n = 2395) were screened by two authors. Sixty studies were eligible. Articles were reviewed for level of evidence, crutch type, participant characteristics, and injury characteristics. There were 42 axillary crutch studies, 12 forearm crutch studies, and 6 studies that did not specify crutch type. These studies incorporated 622 individuals, and most were case series or case reports (n = 54). Axillary crutch use was most commonly associated with axillobrachial arterial complications due to pressure from the axillary bar (n = 34). Forearm crutch use was most commonly associated with compressive neuropathies due to pressure from the forearm cuff (n = 6). Improper crutch fitting and/or use were identified as contributing factors to injury in 22 cases. Duration of crutch use and medical comorbidities also influenced the types of injuries seen. There are rare but potentially serious complications associated with crutch use. When prescribing crutches, clinicians should ensure they are properly fit, engage in appropriate gait training, be aware of common crutch-related injuries, and consider potential patient-specific injury risk factors in order to minimize injury risk.

Outcomes of status epilepticus and their predictors in the elderly-A systematic review.

Status epilepticus (SE) is associated with high mortality and morbidity. Although SE is frequently seen in elderly patients, there is a lack of a cohesive report of outcome measures and associated factors within this population. Our aim was to systematically review studies reporting outcomes of SE among elderly patients and factors influencing these outcomes. A literature search was conducted in PubMed/MEDLINE, EMBASE, CINAHL Complete, and Cochrane Library from database conception to April 22, 2018. A total of 85 studies were included in this systematic review. The included studies show that mortality is higher in elderly patients than in adult patients. Lesional etiologies, higher number of comorbidities, NCSE, RSE, longer hospital and intensive care unit stays, and infection during hospitalization are associated with poor outcome. Future studies should consider measuring functional outcomes, comparative studies between elderly and adults and AED clinical trials specific for elderly with SE.

RasGRP1 is a causal factor in the development of l-DOPA-induced dyskinesia in Parkinson's disease.

The therapeutic effects of l-3,4-dihydroxyphenylalanine (l-DOPA) in patients with Parkinson's disease (PD) severely diminishes with the onset of abnormal involuntary movement, l-DOPA-induced dyskinesia (LID). However, the molecular mechanisms that promote LID remain unclear. Here, we demonstrated that RasGRP1 [(guanine nucleotide exchange factor (GEF)] controls the development of LID. l-DOPA treatment rapidly up-regulated RasGRP1 in the striatum of mouse and macaque model of PD. The lack of RasGRP1 in mice (RasGRP1-/- ) dramatically diminished LID without interfering with the therapeutic effects of l-DOPA. Besides acting as a GEF for Ras homolog enriched in the brain (Rheb), the activator of the mammalian target of rapamycin kinase (mTOR), RasGRP1 promotes l-DOPA-induced extracellular signal-regulated kinase (ERK) and the mTOR signaling in the striatum. High-resolution tandem mass spectrometry analysis revealed multiple RasGRP1 downstream targets linked to LID vulnerability. Collectively, the study demonstrated that RasGRP1 is a critical striatal regulator of LID.

Effect of acetazolamide on susceptibility to central sleep apnea in chronic spinal cord injury.

Spinal cord injury (SCI) is an established risk factor for central sleep apnea. Acetazolamide (ACZ), a carbonic anhydrase inhibitor, has been shown to decrease the frequency of central apnea by inducing mild metabolic acidosis. We hypothesized that ACZ would decrease the propensity to develop hypocapnic central apnea and decrease the apneic threshold. We randomized 16 participants with sleep-disordered breathing (8 SCI and 8 able-bodied controls) to receive ACZ (500 mg twice a day for 3 days) or placebo with a 1-wk washout before crossing over to the other drug arm. Study nights included polysomnography and determination of the hypocapnic apneic threshold and CO2 reserve using noninvasive ventilation. For participants with spontaneous central apnea, CO2 was administered until central apnea was abolished, and CO2 reserve was measured as the difference in end-tidal Pco2 (PETCO2) before and after. Steady-state plant gain, the response of end-tidal Pco2 to changes in ventilation, was calculated from PETCO2 and V̇e ratio during stable sleep. Controller gain, the response of ventilatory drive to changes in end-tidal Pco2, was defined as the ratio of change in V̇e between control and hypopnea to the ΔCO2 during stable non-rapid eye movement sleep. Treatment with ACZ for three days resulted in widening of the CO2 reserve (-4.0 ± 1.2 vs. -3.0 ± 0.7 mmHg for able-bodied, -3.4 ± 1.9 vs. -2.2 ± 2.2 mmHg for SCI, P < 0.0001), and a corresponding decrease in the hypocapnic apnea threshold (28.3 ± 5.2 vs. 37.1 ± 5.6 mmHg for able-bodied, 29.9 ± 5.4 vs. 34.8 ± 6.9 mmHg for SCI, P < 0.0001), respectively. ACZ significantly reduced plant gain when compared with placebo (4.1 ± 1.7 vs. 5.4 ± 1.8 mmHg/L min for able-bodied, 4.1 ± 2.0 vs. 5.1 ± 1.7 mmHg·L-1·min for SCI, P < 0.01). Acetazolamide decreased apnea-hypopnea index (28.8 ± 22.9 vs. 39.3 ± 24.1 events/h; P = 0.05), central apnea index (0.6 ± 1.5 vs. 6.3 ± 13.1 events/h; P = 0.05), and oxyhemoglobin desaturation index (7.5 ± 8.3 vs. 19.2 ± 15.2 events/h; P = 0.01) compared with placebo. Our results suggest that treatment with ACZ decreases susceptibility to hypocapnic central apnea due to decreased plant gain. Acetazolamide may attenuate central sleep apnea and improve nocturnal oxygen saturation, but its clinical utility requires further investigation in a larger sample of patients.NEW & NOTEWORTHY Tetraplegia is a risk factor for central sleep-disordered breathing (SDB) and is associated with narrow CO2 reserve (a marker of susceptibility to central apnea). Treatment with high-dose acetazolamide for 3 days decreased susceptibility to hypocapnic central apnea and reduced the frequency of central respiratory events during sleep. Acetazolamide may play a therapeutic role in alleviating central SDB in patients with cervical spinal cord injury, but larger clinical trials are needed.

Rhes, a striatal-enriched protein, promotes mitophagy via Nix.

Elimination of dysfunctional mitochondria via mitophagy is essential for cell survival and neuronal functions. But, how impaired mitophagy participates in tissue-specific vulnerability in the brain remains unclear. Here, we find that striatal-enriched protein, Rhes, is a critical regulator of mitophagy and striatal vulnerability in brain. In vivo interactome and density fractionation reveal that Rhes coimmunoprecipitates and cosediments with mitochondrial and lysosomal proteins. Live-cell imaging of cultured striatal neuronal cell line shows Rhes surrounds globular mitochondria, recruits lysosomes, and ultimately degrades mitochondria. In the presence of 3-nitropropionic acid (3-NP), an inhibitor of succinate dehydrogenase, Rhes disrupts mitochondrial membrane potential (ΔΨ m ) and promotes excessive mitophagy and cell death. Ultrastructural analysis reveals that systemic injection of 3-NP in mice promotes globular mitochondria, accumulation of mitophagosomes, and striatal lesion only in the wild-type (WT), but not in the Rhes knockout (KO), striatum, suggesting that Rhes is critical for mitophagy and neuronal death in vivo. Mechanistically, Rhes requires Nix (BNIP3L), a known receptor of mitophagy, to disrupt ΔΨ m and promote mitophagy and cell death. Rhes interacts with Nix via SUMO E3-ligase domain, and Nix depletion totally abrogates Rhes-mediated mitophagy and cell death in the cultured striatal neuronal cell line. Finally, we find that Rhes, which travels from cell to cell via tunneling nanotube (TNT)-like cellular protrusions, interacts with dysfunctional mitochondria in the neighboring cell in a Nix-dependent manner. Collectively, Rhes is a major regulator of mitophagy via Nix, which may determine striatal vulnerability in the brain.

Pathologic Alterations in the Proteome of Synaptosomes from a Mouse Model of Spinal Muscular Atrophy.

Spinal muscular atrophy (SMA) is a human genetic disorder characterized by muscle weakness, muscle atrophy, and death of motor neurons. SMA is caused by mutations or deletions in a gene called survival motor neuron 1 (SMN1). SMN1 is a housekeeping gene, but the most prominent pathologies in SMA are atrophy of myofibers and death of motor neurons. Further, degeneration of neuromuscular junctions, of synapses, and of axonal regions are features of SMA disease. Here, we have investigated the proteome dynamics of central synapses in P14 Smn2B/- mice, a model of SMA. Label-free quantitative proteomics on isolated synaptosomes from spinal cords of these animals identified 2030 protein groups. Statistical data analysis revealed 65 specific alterations in the proteome of the central synapses at the early onset stage of disease. Functional analysis of the dysregulated proteins indicated a significant enrichment of proteins associated with mitochondrial dynamics, cholesterol biogenesis, and protein clearance. These pathways represent potential targets for therapy development with the goal of providing stability to the central synapses, thereby preserving neuronal integrity in the context of SMA disease. Data are available via ProteomeXchange with identifier PXD012850.

The effect of caster types on global rolling resistance in manual wheelchairs on indoor and outdoor surfaces.

An important aspect of reducing the strain of wheeling is to decrease rolling resistance. Previous laboratory research, using a treadmill, determined that smaller casters significantly increased rolling resistance. The purpose of this study was to determine the effect of caster size on various indoor and outdoor surfaces on global wheelchair rolling resistance. Three caster types with sizes 4 in, 5 in, and 6 in, three indoor surfaces, and three outdoor surfaces were studied. A manual wheelchair was passively pulled along each surface at 1.11 m/s (3.64 ft/s) by a power wheelchair, and the global rolling resistance of the manual wheelchair was measured using a calibrated force transducer. A 3×3 repeated measures analysis of variance (ANOVA) was conducted for both indoor and outdoor environments. The 4-in casters resulted in the highest global rolling resistance on most surfaces. The 5-in casters had the least rolling resistance on most indoor surfaces, and the 6-in casters had the least rolling resistance on most outdoor surfaces. Although 4-in casters are more popular among active wheelchair users, larger casters were shown to have lower rolling resistance on most surfaces. This study may help users select the best caster size depending upon their daily activities and lifestyle.

Effect of genetic background on the phenotype of the Smn2B/- mouse model of spinal muscular atrophy.

Spinal muscular atrophy (SMA) is caused by mutations or deletions in the Survival Motor Neuron 1 (SMN1) gene in humans. Modifiers of the SMA symptoms have been identified and genetic background has a substantial effect in the phenotype and survival of the severe mouse model of SMA. Previously, we generated the less severe Smn2B/- mice on a mixed genetic background. To assess the phenotype of Smn deficiency on a pure genetic background, we produced Smn2B/2B congenic mice on either the C57BL/6 (BL6) or FVB strain background and characterized them at the 6th generation by breeding to Smn+/- mice. Smn2B/- mice from these crosses were evaluated for growth, survival, muscle atrophy, motor neuron loss, motor behaviour, and neuromuscular junction pathology. FVB Smn2B/- mice had a shorter life span than BL6 Smn2B/- mice (median of 19 days vs. 25 days). Similarly, all other defects assessed occurred at earlier stages in FVB Smn2B/-mice when compared to BL6 Smn2B/-mice. However, there were no differences in Smn protein levels in the spinal cords of these mice. Interestingly, levels of Plastin 3, a putative modifier of SMA, were significantly induced in spinal cords of BL6 Smn2B/- mice but not of FVB Smn2B/-mice. Our studies demonstrate that the phenotype in Smn2B/-mice is more severe in the FVB background than in the BL6 background, which could potentially be explained by the differential induction of genetic modifiers.

S100A8/A9: a Janus-faced molecule in cancer therapy and tumorgenesis.

Correlations exist between the abundance of S100 proteins and disease pathologies. Indeed, this is evidenced by the heterodimeric S100 protein complex S100A8/A9 which has been shown to be involved in inflammatory and neoplastic disorders. However, S100A8/A9 appears as a Janus-faced molecule in this context. On the one hand, it is a powerful apoptotic agent produced by immune cells, making it a very fascinating tool in the battle against cancer. It spears the risk to induce auto-immune response and may serve as a lead compound for cancer-selective therapeutics. In contrast, S100A8/A9 expression in cancer cells has also been associated with tumor development, cancer invasion or metastasis. Clearly, there is a dichotomy and future investigations into the role of S100A8/A9 in cancer biology need to consider both sides of the same coin.

Role of BNIP3 in TNF-induced cell death--TNF upregulates BNIP3 expression.

Tumor necrosis factor alpha (TNF) is a cytokine that induces caspase-dependent (apoptotic) and caspase-independent (necrosis-like) cell death in different cells. We used the murine fibrosarcoma cell line model L929 and a stable L929 transfectant over-expressing a mutated dominant-negative form of BNIP3 lacking the C-terminal transmembrane (TM) domain (L929-DeltaTM-BNIP3) to test if TNF-induced cell death involved pro-apoptotic Bcl2 protein BNIP3. Treatment of cells with TNF in the absence of actinomycin D caused a rapid fall in the mitochondrial membrane potential (DeltaPsim) and a prompt increase in reactive oxygen species (ROS) production, which was significantly less pronounced in L929-DeltaTM-BNIP3. TNF did not cause the mitochondrial release of apoptosis inducing factor (AIF) and Endonuclease G (Endo-G) but provoked the release of cytochrome c, Smac/Diablo, and Omi/HtrA2 at similar levels in both L929 and in L929-DeltaTM-BNIP3 cells. We observed TNF-associated increase in the expression of BNIP3 in L929 that was mediated by nitric oxide and significantly inhibited by nitric oxide synthase inhibitor N5-(methylamidino)-L-ornithine acetate. In L929, lysosomal swelling and activation were markedly increased as compared to L929-DeltaTM-BNIP3 and could be inhibited by treatment with inhibitors to vacuolar H+-ATPase and cathepsins -B/-L. Together, these data indicate that TNF-induced cell death involves BNIP3, ROS production, and activation of the lysosomal death pathway.

S100A8/A9 at low concentration promotes tumor cell growth via RAGE ligation and MAP kinase-dependent pathway.

The complex formed by two members of the S100 calcium-binding protein family, S100A8/A9, exerts apoptosis-inducing activity against various cells, especially tumor cells. Here, we present evidence that S100A8/A9 also has cell growth-promoting activity at low concentrations. Receptor of advanced glycation end product (RAGE) gene silencing and cotreatment with a RAGE-specific blocking antibody revealed that this activity was mediated via RAGE ligation. To investigate the signaling pathways, MAPK phosphorylation and NF-kappaB activation were characterized in S100A8/A9-treated cells. S100A8/A9 caused a significant increase in p38 MAPK and p44/42 kinase phosphorylation, and the status of stress-activated protein kinase/JNK phosphorylation remained unchanged. Treatment of cells with S100A8/A9 also enhanced NF-kappaB activation. RAGE small interfering RNA pretreatment abrogated the S100A8/A9-induced NF-kappaB activation. Our data indicate that S100A8/A9-promoted cell growth occurs through RAGE signaling and activation of NF-kappaB.

S100A8/9 induces cell death via a novel, RAGE-independent pathway that involves selective release of Smac/DIABLO and Omi/HtrA2.

A complex of two S100 EF-hand calcium-binding proteins S100A8/A9 induces apoptosis in various cells, especially tumor cells. Using several cell lines, we have shown that S100A8/A9-induced cell death is not mediated by the receptor for advanced glycation endproducts (RAGE), a receptor previously demonstrated to engage S100 proteins. Investigation of cell lines either deficient in, or over-expressing components of the death signaling machinery provided insight into the S100A8/A9-mediated cell death pathway. Treatment of cells with S100A8/A9 caused a rapid decrease in the mitochondrial membrane potential (DeltaPsi(m)) and activated Bak, but did not cause release of apoptosis-inducing factor (AIF), endonuclease G (Endo G) or cytochrome c. However, both Smac/DIABLO and Omi/HtrA2 were selectively released into the cytoplasm concomitantly with a decrease in Drp1 expression, which inhibits mitochondrial fission machinery. S100A8/A9 treatment also resulted in decreased expression of the anti-apoptotic proteins Bcl2 and Bcl-X(L), whereas expression of the pro-apoptotic proteins Bax, Bad and BNIP3 was not altered. Over-expression of Bcl2 partially reversed the cytotoxicity of S100A8/A9. Together, these data indicate that S100A8/A9-induced cell death involves Bak, selective release of Smac/DIABLO and Omi/HtrA2 from mitochondria, and modulation of the balance between pro- and anti-apoptotic proteins.