Acute effect of Ghrelin on ischemia/reperfusion injury in the rat spinal cord

Molecular Mechanisms and Health Benefits of Ghrelin: A Narrative Review

Ghrelin, an endogenous brain-gut peptide, is secreted in large quantities, mainly from the stomach, in humans and rodents. It can perform the biological function of activating the growth hormone secretagogue receptor (GHSR). Since its discovery in 1999, ample research has focused on promoting its effects on the human appetite and pleasure-reward eating. Extensive, in-depth studies have shown that ghrelin is widely secreted and distributed in tissues. Its role in neurohumoral regulation, such as metabolic homeostasis, inflammation, cardiovascular regulation, anxiety and depression, and advanced cancer cachexia, has attracted increasing attention. However, the effects and regulatory mechanisms of ghrelin on obesity, gastrointestinal (GI) inflammation, cardiovascular disease, stress regulation, cachexia treatment, and the prognosis of advanced cancer have not been fully summarized. This review summarizes ghrelin's numerous effects in participating in a variety of biochemical pathways and the clinical significance of ghrelin in the regulation of the homeostasis of organisms. In addition, potential mechanisms are also introduced.

Ghrelin inhibits early brain injury due to subarachnoid hemorrhage via the Tim-3-mediated HMGB1/NF-κB pathway

OBJECTIVE

To explore the protective effect of Ghrelin on EBI caused by SAH through the HMGB1/NF-κB pathway mediated by Tim-3.

METHODS

Rats were divided into four groups (n = 6): Sham group (Sham), SAH+vehicle group (SAH), SAH + 0.02 μg/kg rhGhrelin group (rhGhrelin-L), SAH + 0.04 μg/kg rhGhrelin group (rhGhrelin-H). At 48 h after SAH, the behavioral impairment in rats was examined for using neurobehavioral scores. The pathological change in the temporal basal brain tissue was observed by HE, and the expression of GHSR-1α and Tim-3 in the temporal basal brain tissue was observed by Western blot. To further validate that rhGhrelin could inhibit SAH-induced EBI by the Tim-3-mediated HMGB1/NF-κB pathway, we treated rats with the AAV-Tim-3. The contents of the inflammatory factors IL-1β, TNF-α, IL-6 was determined by ELISA, apoptosis was detected by TUNEL, the neurons were visualized by Nissl staining, the expression of GHSR-1α，Tim-3, HMGB1, RAGE, NF-κB p65 was determined by Western blot.

RESULTS

Compared with the SAH group, rats treated with rhGhrelin had a significantly lower neurobehavioral score, significantly decreased inflammatory factors IL-1β, TNF-α, IL-6 expression, significantly decreased apoptosis index, and significantly decreased Tim-3, HMGB1, RAGE, NF-κB p65 expression(p < 0.01). The protective effect of rhGhrelin on the SAH-induced EBI was reversed by the AAV-Tim-3.

CONCLUSION

Ghrelin has beneficial effects against SAH-induced EBI by inhibiting the HMGB1/NF-κB pathway, which may be regulated by Tim-3.

Identification of the Fosl1/AMPK/autophagy axis involved in apoptotic and inflammatory effects following spinal cord injury

Strategies for reducing spinal cord injury (SCI) have become a research focus because an effective treatment of SCI is unavailable. The objective of this study was to explore the underlying mechanisms of Fosl1 following SCI. Based on the analysis of the Gene Expression Omnibus (GEO) database, Fosl1 was found to be highly enhanced in SCI. This result was confirmed in our animal model, and Fosl1 was found to be obviously expressed in neurons. Next, we treated PC-12 cells with H₂O₂ to mimic injured neurons and further verified that Fosl1 silencing upregulated AMPK expression, promoted autophagy and inhibited inflammation and apoptosis. Subsequently, a special inhibitor of AMPK was used to examine the role of AMPK, and we learned that the inhibition of AMPK suppressed autophagy and promoted inflammation and apoptosis following Fosl1 silencing. These changes completely reversed the beneficial effects of Fosl1 silencing on injured PC-12 cells. Moreover, treatment with an AMPK activator resulted in effects that were opposite those of the inhibitor. Finally, rats were injected intrathecally with si-Fosl1 to detect its role in vivo. The results showed that si-Fosl1 improved neurological function and decreased apoptosis and inflammation at 14 d postoperation, and the activator further benefited the rats of si-Fosl1 treatment. In conclusion, Fosl1 inhibits autophagy and promotes inflammation and apoptosis through the AMPK signaling pathway following SCI in vivo and in vitro.

Polydatin Attenuates OGD/R-Induced Neuronal Injury and Spinal Cord Ischemia/Reperfusion Injury by Protecting Mitochondrial Function via Nrf2/ARE Signaling Pathway

Spinal cord ischemia/reperfusion injury (SCII) is a devastating complication of spinal or thoracic surgical procedures and can lead to paraplegia or quadriplegia. Neuronal cell damage involving mitochondrial dysfunction plays an important role in the pathogenesis of SCII. Despite the availability of various treatment options, there are currently no mitochondria-targeting drugs that have proven effective against SCII. Polydatin (PD), a glucoside of resveratrol, is known to preserve mitochondrial function in central nervous system (CNS) diseases. The aim of the present study was to explore the neuro- and mito-protective functions of PD and its underlying mechanisms. An in vitro model of SCII was established by exposing spinal cord motor neurons (SMNs) to oxygen–glucose-deprivation/reperfusion (OGD/R), and the cells were treated with different dosages of PD for varying durations. PD improved neuronal viability and protected against OGD/R-induced apoptosis and mitochondrial injury in a dose-dependent manner. In addition, PD restored the activity of neuronal mitochondria in terms of mitochondrial membrane potential (MMP), intracellular calcium levels, mitochondrial permeability transition pore (mPTP) opening, generation of reactive oxygen species (ROS), and adenosine triphosphate (ATP) levels. Mechanistically, PD downregulated Keap1 and upregulated Nrf2, NQO-1, and HO-1 in the OGD/R-treated SMNs. Likewise, PD treatment also reversed the neuronal and mitochondrial damage induced by SCII in a mouse model. Furthermore, the protective effects of PD were partially blocked by the Nrf2 inhibitor. Taken together, PD relieves mitochondrial dysfunction-induced neuronal cell damage by activating the Nrf2/ARE pathway and is a suitable therapeutic option for SCII.

Heal the heart through gut (hormone) ghrelin: a potential player to combat heart failure

Ghrelin, a small peptide hormone (28 aa), secreted mainly by X/A-like cells of gastric mucosa, is also locally produced in cardiomyocytes. Being an orexigenic factor (appetite stimulant), it promotes release of growth hormone (GH) and exerts diverse physiological functions, viz. regulation of energy balance, glucose, and/or fat metabolism for body weight maintenance. Interestingly, administration of exogenous ghrelin significantly improves cardiac functions in CVD patients as well as experimental animal models of heart failure. Ghrelin ameliorates pathophysiological condition of the heart in myocardial infarction, cardiac hypertrophy, fibrosis, cachexia, and ischemia reperfusion injury. This peptide also exerts significant impact at the level of vasculature leading to lowering high blood pressure and reversal of endothelial dysfunction and atherosclerosis. However, the molecular mechanism of actions elucidating the healing effects of ghrelin on the cardiovascular system is still a matter of conjecture. Some experimental data indicate its beneficial effects via complex cellular cross talks between autonomic nervous system and cardiovascular cells, some other suggest more direct receptor-mediated molecular actions via autophagy or ionotropic regulation and interfering with apoptotic and inflammatory pathways of cardiomyocytes and vascular endothelial cells. Here, in this review, we summarise available recent data to encourage more research to find the missing links of unknown ghrelin receptor-mediated pathways as we see ghrelin as a future novel therapy in cardiovascular protection.

Angiopoietin-1 Protects Spinal Cord Ischemia and Reperfusion Injury by Inhibiting Autophagy in Rats

Spinal cord ischemia and reperfusion (SCIR) injury can induce autophagy, which is involved in the survival of neurons. However, whether autophagy plays a neuroprotective or a detrimental role in SCIR injury remains controversial. Angiopoietin-1 (Ang-1), an endothelial growth factor, has been shown to have neuroprotective effects. The present study aimed to explore the neuroprotective mechanisms of Ang-1 in neuronal cells in a rat model of SCIR injury in vivo. Ang-1 protein and rapamycin were injected intrathecally. Basso Beattie Bresnahan (BBB) scoring and hematoxylin and eosin staining were used to assess the degree of SCIR injury. Proteins that reflected the level of autophagy expression, such as Beclin-1 and LC3, were evaluated by western blotting. The results indicated that SCIR injury resulted in loss in lower limb motor function. Ang-1 protein inhibited the expression of Beclin-1 and LC3, which improved the BBB score and alleviated spinal cord injury. In contrast, rapamycin, an autophagy activator, caused the opposite effect. This study provides evidence that Ang-1 plays a neuroprotective role by inhibiting of autophagy expression in SCIR injury. Overall, findings could be useful for the treatment of SCIR injury.

Ghrelin attenuates oxidative stress and neuronal apoptosis via GHSR-1α/AMPK/Sirt1/PGC-1α/UCP2 pathway in a rat model of neonatal HIE

Neuronal apoptosis induced by oxidative stress is one of the major pathological processes involved in neurological impairment after hypoxic-ischemic encephalopathy (HIE). Ghrelin, the unique endogenous ligand for the growth hormone secretagogue receptor-1α (GHSR-1α), could take an anti-apoptotic role in the brain. However, whether ghrelin can attenuate neuronal apoptosis by attenuating oxidative stress after hypoxia-ischemia (HI) insult remains unknown. To investigate the beneficial effects of ghrelin on oxidative stress injury and neuronal apoptosis induced by HI, ten-day old unsexed rat pups were subjected to HI injury and exogenous recombinant human ghrelin(rh-Ghrelin) was administered intranasally at 1 h and 24 h after HI induction. [D-Lys³]-GHRP-6, a selective inhibitor of GHSR-1α and Ex527, a selective inhibitor of GHSR-1α were administered intranasally at 1 h before HI induction respectively. Small interfering ribonucleic acid (siRNA) for GHSR-1α were administered by intracerebroventricular (i.c.v) injection at 24 h before HI induction. Neurological tests, immunofluorescence, MitoSox staining, Fluoro-Jade C staining, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, and western blot experiments were performed. Our results indicated that ghrelin significantly improved neurobehavioral outcomes and reduced oxidative stress and neuronal apoptosis. Moreover, ghrelin treatment significantly promoted phosphorylation of AMPK, upregulated the expression of Sirt1, PGC-1α, UCP2 and the ratio of Bcl2/Bax, while it downregulated cleaved caspase-3 levels. The protective effects of ghrelin were reversed by [D-Lys³]-GHRP-6, GHSR-1α siRNA or Ex527. In conclusion, our data demonstrated that ghrelin reduced oxidative stress injury and neuronal apoptosis which was in part via the GHSR-1α/AMPK/Sirt1/PGC-1α/UCP2 signalling pathway after HI. Ghrelin may be a novel therapeutic target for treatment after neonatasl HI injury.

Hydrogen sulfide plays an important protective role by influencing autophagy in diseases

Autophagy can regulate cell growth, proliferation, and stability of cell environment. Its dysfunction can be involved in a variety of diseases. Hydrogen sulfide (H(2)S) is an important signaling molecule that regulates many physiological and pathological processes. Recent studies indicate that H(2)S plays an important protective role in many diseases through influencing autophagy, but its mechanism is not fully understood. This article reviewed the progress about the effect of H(2)S on autophagy in diseases in recent years in order to provide theoretical basis for the further research on the interaction of H(2)S and autophagy and the mechanisms involved.

The Role of Ghrelin in Anorexia Nervosa

Ghrelin, a 28-amino acid peptide hormone expressed in X/A-like endocrine cells of the stomach, is the only known peripherally produced and centrally acting peptide that stimulates food intake and therefore attracted a lot of attention with one major focus on the treatment of conditions where an increased energy intake or body weight gain is desired. Anorexia nervosa is an eating disorder characterized by a pronounced reduction of body weight, a disturbed body image and hormonal alterations. Ghrelin signaling has been thoroughly investigated under conditions of anorexia nervosa. The present review will highlight these alterations of ghrelin in anorexia and discuss possible treatment strategies targeting ghrelin signaling. Lastly, gaps in knowledge will be mentioned to foster future research.

Administration of ghrelin associated with decreased expression of matrix metalloproteinase-9 following normobaric systemic hypoxia in the brain

OBJECTIVE

According to our previous studies, ghrelin protects blood brain barrier (BBB) integrity and it attenuates hypoxia-induced brain edema in the hypoxic conditions. However, the underlying mechanisms remain poorly understood. Several studies suggest a role for matrix metal-loproteinase-9 (MMP9) in the BBB disruption and cerebral edema formation. The present study was conducted to determine the effect of ghrelin on MMP9 protein expression in the model of acute and chronic systemic hypoxia.

METHODS

Adult male Wistar rats were divided into acute or chronic controls, acute or chronic hypoxia and ghrelin-treated acute or chronic hypoxia groups. The hypoxic groups were kept in the hypoxic chamber (10-11% O2) for two (acute) or ten days (chronic). Effect of ghrelin on MMP9 protein expression was assessed using immunoblotting.

RESULTS

Our results showed that acute and chronic systemic hypoxia increased the MMP9 protein expression in the brain (p<0.001). Treatment with ghrelin significantly attenuated this expression in the cerebral hypoxia (p<0.05).

CONCLUSION

Our results demonstrate that the neuroprotective effects of ghrelin may be mediated, in part, by decreasing in MMP9 production in the hypoxic brain.

Insulin-Like Growth Factor-1 as a Possible Alternative to Bone Morphogenetic Protein-7 to Induce Osteogenic Differentiation of Human Mesenchymal Stem Cells in Vitro

Growth factors and mesenchymal stem cells (MSC) support consolidation of bone defects. Bone Morphogenetic Protein-7 (BMP-7) has been used clinically and experimentally, but the outcomes remain controversial. Increased systemic expression of Insulin-like Growth Factor-1 (IGF-1) significantly correlates with successful regeneration of bone healing disorders, making IGF-1 a promising alternative to BMP-7. There is no experimental data comparing the osteoinductive potential of IGF-1 and BMP-7. Therefore, in this study, the influence of IGF-1 and BMP-7 in different concentrations on the osteogenic differentiation of two human MSC-subtypes, isolated from reaming debris (RMSC) and iliac crest bone marrow (BMSC) has been assessed. A more sensitive reaction of BMSC towards stimulation with IGF-1 in concentrations of 400–800 ng/mL was found, leading to a significantly higher degree of osteogenic differentiation compared to stimulation with BMP-7. RMSC react more sensitively to stimulation with BMP-7 compared to BMSC. Lower concentrations of IGF-1 were necessary to significantly increase osteogenic differentiation of RMSC and BMSC compared to BMP-7. Therefore, IGF-1 should be considered as a valuable option to improve osteogenic differentiation of MSC and merits further experimental consideration. The MSC subtype and method of differentiation factor application also have to be considered, as they affect the outcome of osteogenic differentiation.

Evaluation of mTOR signaling pathway proteins in rat gastric mucosa exposed to sulfite and ghrelin

BACKGROUND/AIMS

Mammalian target of rapamycin (mTOR) signaling serves as a central regulator of cell growth, proliferation, and survival. In this study, we planned to evaluate the expressions of mTOR signaling constituents (p-p70S6K, p-mTOR, and p-Tuberin) in rat gastric mucosa and to compare the results in sulfite- and sulfite+ghrelin-exposed groups.

MATERIALS AND METHODS

Rats were divided into three groups: the control group (C), the sodium metabisulfite (Na2S2O5) (S) group, and sulfite+ghrelin (SG) group. Sodium metabisulfite at 100 mg/kg/day was administered via gavage, and ghrelin at 20 μg/kg/day was administered intraperitoneally for 35 days. We have used immunohistochemistry for mTOR signaling pathway components.

RESULTS

There were no significant differences for p-p70S6K and p-mTOR expression among the C, S, and SG groups. Tuberin expression was significantly increased in the S group compared to the C group. Furthermore, tuberin expression was found to be significantly decreased in the SG group.

CONCLUSION

This study is the first one in the literature that shows the expression of mTOR signaling proteins in gastric mucosa of rats exposed to sulfite and ghrelin. Furthermore, it demonstrates that ghrelin treatment reduces p-Tuberin expression induced by ingested sulfite.

The inhibition of microRNA-31 weakens acute spinal cord injury through nuclear factor-κB and TGF-β/Smad 2 in rat

Therefore, the aim of the present study is to evaluate that the therapeutic potential of microRNA-31 after spinal cord injury (SCI) in rats and to expound the potential neuroprotective mechanisms. In SCI model, microRNA-31 expression was up-regulated, compared with negative group. In vitro model, over-expression of microRNA-31 increases cell apoptosis and inflammation, compared with negative control group. Over-expression of microRNA-31 induced nuclear factor-κB (NF-κB), TGF-β and p-Smad 2 protein expression in vitro model of SCI, compared with negative control group. NF-κB inhibitor suppressed the effects of microRNA-31 on inflammation of vitro model of SCI. Meanwhile, TGF-β inhibitor suppressed the effects of microRNA-31 on apoptosis of in vitro model of SCI. The results clearly show that anti-microRNA-31 weakens inflammation and apoptosis by NF-κB and TGF-β/Smad 2 pathway in SCI.

Hydrogen Sulfide Inhibits Autophagic Neuronal Cell Death by Reducing Oxidative Stress in Spinal Cord Ischemia Reperfusion Injury

Autophagy is upregulated in spinal cord ischemia reperfusion (SCIR) injury; however, its expression mechanism is largely unknown; moreover, whether autophagy plays a neuroprotective or neurodegenerative role in SCIR injury remains controversial. To explore these issues, we created an SCIR injury rat model via aortic arch occlusion. Compared with normal controls, autophagic cell death was upregulated in neurons after SCIR injury. We found that autophagy promoted neuronal cell death during SCIR, shown by a significant number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling- (TUNEL-) positive cells colabeled with the autophagy marker microtubule-associated protein 1 light chain 3, while the autophagy inhibitor 3-methyladenine reduced the number of TUNEL-positive cells and restored neurological and motor function. Additionally, we showed that oxidative stress was the main trigger of autophagic neuronal cell death after SCIR injury and N-acetylcysteine inhibited autophagic cell death and restored neurological and motor function in SCIR injury. Finally, we found that hydrogen sulfide (H₂S) inhibited autophagic cell death significantly by reducing oxidative stress in SCIR injury via the AKT-the mammalian target of rapamycin (mTOR) pathway. These findings reveal that oxidative stress induces autophagic cell death and that H₂S plays a neuroprotective role by reducing oxidative stress in SCIR.

Protective roles of bioactive peptides during ischemia-reperfusion injury: From bench to bedside

Ischemia-reperfusion (I/R) is a well-known pathological condition which may lead to disability and mortality. I/R injury remains an unresolved and complicated situation in a number of clinical conditions, such as cardiac arrest with successful reanimation, as well as ischemic events in brain and heart. Peptides have many attractive advantages which make them suitable candidate drugs in treating I/R injury, such as low toxicity and immunogenicity, good solubility property, distinct tissue distribution pattern, and favorable pharmacokinetic profile. An increasing number of studies indicate that peptides could protect against I/R injury in many different organs and tissues. Peptides also face several therapeutic challenges that limit their clinical application. In this review, we present the mechanisms of action of peptides in reducing I/R injury, as well as further discuss modification strategies to improve the functional properties of bioactive peptides.

Nicotinamide Adenine Dinucleotide Protects against Spinal Cord Ischemia Reperfusion Injury-Induced Apoptosis by Blocking Autophagy

The role of autophagy, neuroprotective mechanisms of nicotinamide adenine dinucleotide (NAD⁺), and their relationship in spinal cord ischemic reperfusion injury (SCIR) was assessed. Forty-eight Sprague-Dawley rats were divided into four groups: sham, ischemia reperfusion (I/R), 10 mg/kg NAD⁺, and 75 mg/kg NAD⁺. Western blotting, immunofluorescence, and immunohistochemistry were used to assess autophagy and apoptosis. Basso, Beattie, and Bresnahan (BBB) scores were used to assess neurological function. Expression levels of Beclin-1, Atg12-Atg5, LC3B-II, cleaved caspase 3, and Bax were upregulated in the I/R group and downregulated in the 75 mg/kg NAD⁺ group; p-mTOR, p-AKT, p62, and Bcl-2 were downregulated in the I/R group and upregulated in the 75 mg/kg NAD⁺ group. Numbers of LC3B-positive, caspase 3-positive, Bax-positive, and TUNEL-positive cells were significantly increased in the I/R group and decreased in the 75 mg/kg NAD⁺ group. The mean integrated option density of Bax increased and that of Nissl decreased in the I/R group, and it decreased and increased, respectively, in the 75 mg/kg NAD⁺ group. BBB scores significantly increased in the 75 mg/kg NAD⁺ group relative to the I/R group. No difference was observed between I/R and 10 mg/kg NAD⁺ groups for these indicators. Therefore, excessive and sustained autophagy aggravates SCIR; administration of NAD⁺ alleviates injury.

Ghrelin and the Cardiovascular System

Ghrelin is a small peptide released primarily from the stomach. It is a potent stimulator of growth hormone secretion from the pituitary gland and is well known for its regulation of metabolism and appetite. There is also a strong relationship between ghrelin and the cardiovascular system. Ghrelin receptors are present throughout the heart and vasculature and have been linked with molecular pathways, including, but not limited to, the regulation of intracellular calcium concentration, inhibition of proapoptotic cascades, and protection against oxidative damage. Ghrelin shows robust cardioprotective effects including enhancing endothelial and vascular function, preventing atherosclerosis, inhibiting sympathetic drive, and decreasing blood pressure. After myocardial infarction, exogenous administration of ghrelin preserves cardiac function, reduces the incidence of fatal arrhythmias, and attenuates apoptosis and ventricular remodeling, leading to improvements in heart failure. It ameliorates cachexia in end-stage congestive heart failure patients and has shown clinical benefit in pulmonary hypertension. Nonetheless, since ghrelin's discovery is relatively recent, there remains a substantial amount of research needed to fully understand its clinical significance in cardiovascular disease.

The neurological effects of ghrelin in brain diseases: Beyond metabolic functions

Ghrelin, a peptide released by the stomach that plays a major role in regulating energy metabolism, has recently been shown to have effects on neurobiological behaviors. Ghrelin enhances neuronal survival by reducing apoptosis, alleviating inflammation and oxidative stress, and accordingly improving mitochondrial function. Ghrelin also stimulates the proliferation, differentiation and migration of neural stem/progenitor cells (NS/PCs). Additionally, the ghrelin is benefit for the recovery of memory, mood and cognitive dysfunction after stroke or traumatic brain injury. Because of its neuroprotective and neurogenic roles, ghrelin may be used as a therapeutic agent in the brain to combat neurodegenerative disease. In this review, we highlight the pre-clinical evidence and the proposed mechanisms underlying the role of ghrelin in physiological and pathological brain function.

Exogenous Ghrelin Accelerates the Healing of Acetic Acid-Induced Colitis in Rats

Previous studies have shown that ghrelin reduces colonic inflammation induced by trinitrobenzene sulfonic acid and dextran sodium sulfate. In the present study we determined the effect of treatment with ghrelin on the course of acetic acid-induced colitis in rats. Rectal administration of 3% acetic acid solution led to induction of colitis in all animals. Damage of the colonic wall was accompanied by an increase in mucosal concentration of pro-inflammatory interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), as well mucosal activity of myeloperoxidase. Moreover, induction of colitis led to a reduction in colonic blood flow and DNA synthesis. Administration of ghrelin after induction of colitis led to faster regeneration of the colonic wall and reduction in colonic levels of IL-1β, TNF-α, and myeloperoxidase. In addition, treatment with ghrelin improved mucosal DNA synthesis and blood flow. Our study disclosed that ghrelin exhibits a strong anti-inflammatory and healing effect in acetic acid-induced colitis. Our current observation in association with previous findings that ghrelin exhibits curative effect in trinitrobenzene sulfonic acid- and dextran sodium sulfate-induced colitis suggest that therapeutic effect of ghrelin in the colon is universal and independent of the primary cause of colitis.

Protective actions of des-acylated ghrelin on brain injury and blood–brain barrier disruption after stroke in mice

Stroke is a leading cause of death, but treatments are limited. This experimental study reveals that the hormone ghrelin powerfully protects the brain and its blood vessels against injury after stroke, raising the possibility that it could be exploited therapeutically.

Effects of Aloe Vera on Spinal Cord Ischemia-Reperfusion Injury of Rats

AIM

The purpose of this study was to evaluate the possible protective/therapeutic effects of aloe vera (AV) on ischemia-reperfusion injury (I/R) of spinal cord in rats.

MATERIALS AND METHODS

A total of 28 Wistar Albino rats were divided into four random groups of equal number (n = 7). Group I (control) had no medication or surgery; Group II underwent spinal cord ischemia and was given no medication; Group III was administered AV by gastric gavage for 30 days as pre-treatment; Group IV was administered single dose intraperitoneal methylprednisolone (MP) after the ischemia. Nuclear respiratory factor-1 (NRF1), malondialdehyde (MDA) and superoxide dismutase (SOD) levels were evaluated. Tissue samples were examined histopathologically and neuronal nitric oxide synthase (nNOS) and nuclear factor-kappa B (NF-κB) protein expressions were assessed by immunohistochemical staining.

RESULTS

NRF1 and SOD levels of ischemia group were found to be lower compared to the other groups. MDA levels significantly increased after I/R. Treatment with AV and MP resulted in reduced MDA levels and also alleviated hemorrhage, edema, inflammatory cell migration and neurons were partially protected from ischemic injury. When AV treatment was compared with MP, there was no statistical difference between them in terms of reduction of neuronal damage. I/R injury increased NF-κB and nNOS expressions. AV and MP treatments decreased NF-κB and nNOS expressions.

CONCLUSIONS

It was observed that aloe vera attenuated neuronal damage histopathologically and biochemically as pretreatment. Further studies may provide more evidence to determine the additional role of aloe vera in spinal cord ischemia reperfusion injury.

Ghrelin partially protects against cisplatin-induced male murine gonadal toxicity in a GHSR-1a-dependent manner

The chemotherapeutic drug cisplatin causes a number of dose-dependent side effects, including cachexia and testicular damage. Patients receiving a high cumulative dose of cisplatin may develop permanent azoospermia and subsequent infertility. Thus, the development of chemotherapeutic regimens with the optimal postsurvival quality of life (fertility) is of high importance. This study tested the hypothesis that ghrelin administration can prevent or minimize cisplatin-induced testicular damage and cachexia. Ghrelin and its receptor, the growth hormone secretagogue receptor (GHSR-1a), are expressed and function in the testis. Targeted deletion of ghrelin, or its receptor, significantly increases the rate of cell death in the testis, suggesting a protective role. Intraperitoneal administration of vehicle, ghrelin, or cisplatin alone or in combination with ghrelin, in cycles of 9 or 18 days, to adult male C57Bl/6 mice was performed. Body weight was measured daily and testicular and epididymal weight, sperm density and motility, testicular histology, and testicular cell death were analyzed at the time of euthanization. Ghrelin coadministration decreased the severity of cisplatin-induced cachexia and gonadal toxicity. Body, testicular, and epididymal weights significantly increased as testicular cell death decreased with ghrelin coadministration. The widespread damage to the seminiferous epithelium induced by cisplatin administration was less severe in mice simultaneously treated with ghrelin. Furthermore, ghrelin diminished the deleterious effects of cisplatin on testis and body weight homeostasis in wild-type but not Ghsr(-/-) mice, showing that ghrelin's actions are mediated via GHSR. Ghrelin or more stable GHSR agonists potentially offer a novel therapeutic approach to minimize the testicular damage that occurs after gonadotoxin exposure.

Effects of ghrelin on sepsis-induced acute kidney injury: one step forward

BACKGROUND

Among the several disorders induced by sepsis, acute kidney injury (AKI) represents the most important economic burden problem that is associated with high mortality and morbidity rates. The aim of this study was to investigate the anti-inflammatory effects of ghrelin in sepsis-induced AKI and the possible role of vagus nerve.

METHODS

Five groups were included: sham, cecal ligation and puncture (CLP), CLP-ghrelin, CLP-vagotomy and CLP-vagotomy-ghrelin group.

RESULTS

Ghrelin treatment immediately after induction of CLP, significantly improved renal Glomerular filtration rate (GFR), serum creatinine, BUN and renal necrosis score as compared to the unprotected CLP group. In addition, ghrelin significantly decreased renal TNF alpha (111.5 ± 10.35 vs. 291.8 ± 15.8 pg/mg ptn), VCAM1 (6.28 ± 1.7 vs. 12.9 ± 1.2 µ/g ptn) and MPO (0.95 ± 0.13 vs. 2.5 ± 0.4 µ/g ptn) without significant increase in renal IL-10. Those effects were abolished by vagotomy.

CONCLUSION

We concluded that ghrelin could represent new therapeutic window in early treatment of sepsis-induced AKI and this could be mainly due to its anti-inflammatory effects.

Supplement zinc as an effective treatment for spinal cord ischemia/reperfusion injury in rats

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) plays a key role in the pathophysiology process and therapy of spinal cord injury (SCI). Accordingly, zinc regulates the expression of BDNF and its receptor in the central nervous system, the mechanism of which is still unknown. The present study investigates whether supplement zinc could reduce neurological damage in a rat model, with spinal cord ischemia-reperfusion (I/R) injury and how the effect of zinc transporter 1(ZnT-1) was involved.

METHODS

100 Sprague-Dawley male rats were randomly and evenly divided into four groups. They were subjected to spinal cord ischemia by clamping the abdominal aorta for 45 min. Rats in the zinc-deficient dietary model group (ZD), zinc-adequate dietary model group (ZA), and zinc-high dietary model group (ZH) were given free access to purified diet, containing 5, 30, or 180 mg Zn/kg. Sham operation rats were subjected to laparotomy without clamping of the aorta and were fed by ZA diet (30 mg Zn/kg). Neurological function was scored by Tarlov's score. The spinal cord segments (L5) were harvested for histological examination, auto-metallographic (AMG) analysis, myeloperoxidase (MPO) activity analysis, expression of ZnT-1 and BDNF.

RESULTS

The rats in the ZH group have shown the higher neurological scores, slighter histological changes and the attenuated MPO activity, compared with those in the ZD and ZA groups at the four observation time points (p<0.05). The AMG staining density in the ZH group was significantly higher than that of ZD group in 14 days later after the operation. Compared with other groups, ZH group's expression of Zn-T1 and BDNF were significantly increased, and was positively correlated with the same time points after surgery (Spearman rho=0.403, p=0.0152.)

CONCLUSION

These findings suggest that zinc supplement can significantly reduce the spinal cord I/R injury in rats. The mechanism may be related with restraining the MPO activity and increasing of ZnT-1, which promoted the synthesis and release of BDNF.

Monitoring somatosensory evoked potentials in spinal cord ischemia-reperfusion injury

It remains unclear whether spinal cord ischemia-reperfusion injury caused by ischemia and other non-mechanical factors can be monitored by somatosensory evoked potentials. Therefore, we monitored spinal cord ischemia-reperfusion injury in rabbits using somatosensory evoked potential detection technology. The results showed that the somatosensory evoked potential latency was significantly prolonged and the amplitude significantly reduced until it disappeared during the period of spinal cord ischemia. After reperfusion for 30–180 minutes, the amplitude and latency began to gradually recover; at 360 minutes of reperfusion, the latency showed no significant difference compared with the pre-ischemic value, while the somatosensory evoked potential amplitude in-creased, and severe hindlimb motor dysfunctions were detected. Experimental findings suggest that changes in somatosensory evoked potential latency can reflect the degree of spinal cord ischemic injury, while the amplitude variations are indicators of the late spinal cord reperfusion injury, which provide evidence for the assessment of limb motor function and avoid iatrogenic spinal cord injury.

Development and treatments of inflammatory cells and cytokines in spinal cord ischemia-reperfusion injury

During aortic surgery, interruption of spinal cord blood flow might cause spinal cord ischemia-reperfusion injury (IRI). The incidence of spinal cord IRI after aortic surgery is up to 28%, and patients with spinal cord IRI might suffer from postoperative paraplegia or paraparesis. Spinal cord IRI includes two phases. The immediate spinal cord injury is related to acute ischemia. And the delayed spinal cord injury involves both ischemic cellular death and reperfusion injury. Inflammation is a subsequent event of spinal cord ischemia and possibly a major contributor to spinal cord IRI. However, the development of inflammatory mediators is incompletely demonstrated. And treatments available for inflammation in spinal cord IRI are insufficient. Improved understanding about spinal cord IRI and the development of inflammatory cells and cytokines in this process will provide novel therapeutic strategies for spinal cord IRI. Inflammatory cytokines (e.g., TNF-α and IL-1) may play an important role in spinal cord IRI. For treatment of several intractable autoimmune diseases (e.g., rheumatoid arthritis), where inflammatory cytokines are involved in disease progression, anti-inflammatory cytokine antagonist is now available. Hence, there is great potential of anti-inflammatory cytokine antagonist for therapeutic use of spinal cord IRI. We here review the mediators and several possibilities of treatment in spinal cord IRI.

Ischemic preconditioning protects against spinal cord ischemia-reperfusion injury in rabbits by attenuating blood spinal cord barrier disruption

Ischemic preconditioning has been reported to protect against spinal cord ischemia-reperfusion (I-R) injury, but the underlying mechanisms are not fully understood. To investigate this, Japanese white rabbits underwent I-R (30 min aortic occlusion followed by reperfusion), ischemic preconditioning (three cycles of 5 min aortic occlusion plus 5 min reperfusion) followed by I-R, or sham surgery. At 4 and 24 h following reperfusion, neurological function was assessed using Tarlov scores, blood spinal cord barrier permeability was measured by Evan’s Blue extravasation, spinal cord edema was evaluated using the wet-dry method, and spinal cord expression of zonula occluden-1 (ZO-1), matrix metalloproteinase-9 (MMP-9), and tumor necrosis factor-α (TNF-α) were measured by Western blot and a real-time polymerase chain reaction. ZO-1 was also assessed using immunofluorescence. Spinal cord I-R injury reduced neurologic scores, and ischemic preconditioning treatment ameliorated this effect. Ischemic preconditioning inhibited I-R-induced increases in blood spinal cord barrier permeability and water content, increased ZO-1 mRNA and protein expression, and reduced MMP-9 and TNF-α mRNA and protein expression. These findings suggest that ischemic preconditioning attenuates the increase in blood spinal cord barrier permeability due to spinal cord I-R injury by preservation of tight junction protein ZO-1 and reducing MMP-9 and TNF-α expression.

The role of ghrelin in neuroprotection after ischemic brain injury

Ghrelin, a gastrointestinal peptide with a major role in regulating feeding and metabolism, has recently been investigated for its neuroprotective effects. In this review we discuss pre-clinical evidence suggesting ghrelin may be a useful therapeutic in protecting the brain against injury after ischemic stroke. Specifically, we will discuss evidence showing ghrelin administration can improve neuronal cell survival in animal models of focal cerebral ischemia, as well as rescue memory deficits. We will also discuss its proposed mechanisms of action, including anti-apoptotic and anti-inflammatory effects, and suggest ghrelin treatment may be a useful intervention after stroke in the clinic.

Ghrelin inhibits sodium metabisulfite induced oxidative stress and apoptosis in rat gastric mucosa

This study aimed to investigate the effect of ghrelin administration on sulfite induced oxidative and apoptotic changes in rat gastric mucosa. Forty male albino Wistar rats were randomized into control (C), sodium metabisulfite (Na2S2O5) treated (S), ghrelin treated (G) and, Na2S2O5+ghrelin treated (SG) groups. Sodium metabisulfite (100 mg/kg/day) was given by gastric gavage and, ghrelin (20 μg/kg/day) was given intraperitoneally for 5 weeks. Plasma-S-sulfonate level was increased in S and SG groups. Na2S2O5 administration significantly elevated total oxidant status (TOS) levels while depleting total antioxidant status (TAS) levels in gastric mucosa. Ghrelin significantly decreased gastric TOS levels in the SG group compared with the S group. Additionally, TAS levels were found to be higher in SG group in reference to S group. Na2S2O5 administration also markedly increased the number of apoptotic cells, cleaved caspase-3 and PAR expression (PARP activity indicator) and, decreased Ki67 expression (cell proliferation index) in gastric mucosal cells. Ghrelin treatment decreased the number apoptotic cells, cytochrome C release, PAR and, caspase-3 expressions while increasing Ki67 expression in gastric mucosa exposed to Na2S2O5. In conclusion, we suggest that ghrelin treatment might ameliorate ingested-Na2S2O5 induced gastric mucosal injury stemming from apoptosis and oxidative stress in rats.

Ghrelin: a novel neuromuscular recovery promoting factor?

Promoting neuromuscular recovery after neural injury is a major clinical issue. While techniques for nerve reconstruction are continuously improving and most peripheral nerve lesions can be repaired today, recovery of the lost function is usually unsatisfactory. This evidence claims for innovative nonsurgical therapeutic strategies that can implement the outcome after neural repair. Although no pharmacological approach for improving posttraumatic neuromuscular recovery has still entered clinical practice, various molecules are explored in experimental models of neural repair. One of such molecules is the circulating peptide hormone ghrelin. This hormone has proved to have a positive effect on neural repair after central nervous system lesion, and very recently its effectiveness has also been demonstrated in preventing posttraumatic skeletal muscle atrophy. By contrast, no information is still available about its effectiveness on peripheral nerve regeneration although preliminary data from our laboratory suggest that this molecule can have an effect also in promoting axonal regeneration after nerve injury and repair. Should this be confirmed, ghrelin might represent an ideal candidate as a therapeutic agent for improving posttraumatic neuromuscular recovery because of its putative effects at all the various structural levels involved in this regeneration process, namely, the central nervous system, the peripheral nerve, and the target skeletal muscle.