Effects of erythropoietin and methylprednisolone on AQP4 expression in astrocytes

Therapeutic strategies that modulate the acute phase of secondary spinal cord injury scarring and inflammation and improve injury outcomes

INTRODUCTION

The acute phase of secondary spinal cord injury (SCI) is a crucial therapeutic window to mitigate ongoing damage and promote tissue repair. The present systematic review critically evaluates the efficacy and safety of current management modalities for this phase, identifying gaps in knowledge and providing insights for future research directions.

METHODS

In December 2024, PubMed, Web of Science, Google Scholar, and Embase were accessed with no time constraints. All the clinical studies investigating the pharmacological management of secondary SCI were accessed.

RESULTS

Data from 3017 patients (385 women) were collected. The mean length of the follow-up was 6 ± 3.4 months, and the mean age of the patients was 43.3 ± 10.3 years.

CONCLUSION

Erythropoietin (EPO) improves motor function, reduces impairment in secondary spinal cord injury, modulates antioxidation and neurogenesis, and minimizes apoptosis and inflammation. Although commonly administered, methylprednisolone shows uncertain efficacy. The rho-GTPases inhibitor VX-210 and levetiracetam did not demonstrate effectiveness in treatment. Monosialotetrahexosylganglioside Sodium Salt (GM-1) and riluzole are associated with favorable neurological outcomes. Granulocyte Colony-Stimulating Factor (G-CSF) and Hepatocyte Growth Factor (HGF) offer improved motor scores with fewer side effects.

Erythropoietin and glial cells in central and peripheral nervous systems

Erythropoietin (EPO) is the main hematopoietic growth factor prescribed to overcome anemia. It is also a neuroprotective agent. EPO binds to the erythropoietin receptor (EPOR), expressed on neurons and glial cells in the central nervous system (CNS), and exerts its neuroprotective potencies through the EPO-EPOR complex. The mechanism of the signal transduction pathways of EPO on glial cells is defined. EPO-EPOR complex can affect neurological disorders, such as Alzheimer's disease, Parkinson's disease, ischemia, retinal injury, stroke, hypoxia, trauma, and demyelinating diseases, through acting downstream signaling pathways. This review focuses on the roles of EPO in different types of glial cells (astrocytes, microglia, oligodendrocytes, and Schwann cells) and their relationships with signaling pathways. Information on the non-erythropoietic action of EPO and related signaling systems in connection with glial cells could enhance EPO treatment to restore different CNS disorders and propose new perspectives on the neuroprotective potential of EPO.

Multivalent Display of Erythropoietin on Quantum Dots Enhances Aquaporin-4 Expression and Water Transport in Human Astrocytes In Vitro

In mammalian cells, growth factor-induced intracellular signaling and protein synthesis play a critical role in cellular physiology and homeostasis. In the brain's glymphatic system (GS), the water-conducting activity of aquaporin-4 (AQPN-4) membrane channels (expressed in polarized fashion on astrocyte end-feet) mediates the clearance of wastes through the convective transport of fluid and solutes through the perivascular space. The glycoprotein erythropoietin (EPO) has been shown to induce the astrocyte expression of AQPN-4 via signaling through the EPO receptor and the JAK/STAT signaling pathway. Here, we self-assemble EPO in a multivalent fashion onto the surface of semiconductor quantum dots (QDs) (driven by polyhistidine-based self-assembly) to drive the interaction of the bioconjugates with EPOR on human astrocytes (HA). This results in a 2-fold augmentation of JAK/STAT signaling activity and a 1.8-fold enhancement in the expression of AQPN-4 in cultured primary HA compared to free EPO. This translates into a 2-fold increase in the water transport rate in HA cells as measured by the calcein AM water transport assay. Importantly, EPO-QD-induced augmented AQPN-4 expression does not elicit any deleterious effect on the astrocyte viability. We discuss our results in the context of the implications of EPO-nanoparticle (NP) bioconjugates for use as research tools to understand the GS and their potential as therapeutics for the modulation of GS function. More generally, our results illustrate the utility of NP bioconjugates for the controlled modulation of growth factor-induced intracellular signaling.

A hydrogen sulfide donor suppresses pentylenetetrazol-induced seizures in rats via PKC signaling

Epilepsy is a serious neurological disorder. Available antiepileptic drugs are still lacking. Hydrogen sulfide (H2S), a neuron-protective endogenous gasotransmitter, is reported to have effect on epilepsy. But it remains to be determined for its mechanism. In the present study, we found that a novel carbazole-based H2S donor could effectively suppress pentylenetetrazol-induced seizures in rats. The H2S donor could alleviate not only the epileptic behavior of animals but also the hippocampal EEG activity of seizures. The H2S donor down-regulated the expression of aquaporin 4 in the hippocampus of epilepsy rats. The H2S donor also decreased the seizure-induced release of inflammatory cytokines including IL-1β, IL-6 and TNF-α. In addition, the H2S donor increased protein kinase C (PKC) expression in the hippocampus of epilepsy rats. These effects of the H2S donor on epilepsy rats were attenuated after blockade of PKC signaling by Go6983, suggesting that PKC signaling participated in the antiepileptic process of H2S donor. Taken together, the H2S donor has a beneficial effect on epilepsy control in a PKC-dependent manner.

The Efficacy of Combined Medication With Methylprednisolone and Erythropoietin in the Treatment of Ischemia-Reperfusion Injury to the Spinal Cord in Patients With Cervical Spondylotic Myelopathy

Introduction

Cervical myelopathy (CM) is caused by degenerative or congenital changes in the discs and soft tissues of the cervical spine, leading to chronic compression of the spinal cord. The current treatment for moderate-to-severe CM is surgical decompression, which is effective in most cases; however, it can cause inflammation of the nervous system and spinal cord reperfusion injury, resulting in perioperative neurological complications and suboptimal neurological recovery. The aim of this study was to investigate the therapeutic effects of the combination of erythropoietin and methylprednisolone in the treatment of ischemia-reperfusion injury to the spinal cord and to analyze its effects on the levels of interleukin-1 beta (IL-1β), interleukin-1 receptor antagonist (IL-1RA), and interleukin-8 (IL-8).

Materials and methods

This study included 110 patients admitted to the hospital due to cervical spondylotic myelopathy. They were randomized into two groups of 55 patients each: a control and an observation group. In both groups of patients, fusion internal fixation and anterior cervical discectomy were performed. The difference, however, was that the control group received a rapid intravenous injection of 30 mg/kg methylprednisolone 30 minutes prior to spinal cord decompression, while the observation group received an intravenous injection of 30 mg/kg methylprednisolone and 3,000 U/kg erythropoietin 30 minutes before spinal cord decompression. The study was approved by the Hospital Ethical Committee of the Dow University of Health Sciences, Karachi. The neurological function of both groups of patients was assessed before the procedure and three months after the treatment using the Japanese Orthopedic Association (JOA) method of assessing spinal cord function (40-point rating method). Enzyme-linked immunosorbent assay (ELISA) was performed to measure the levels of neuron-specific enolase (NSE), S-100β, IL-1RA, IL-1β, and IL-8 in both groups. The quality of life of patients in both groups was assessed three months after the treatment with the World Health Organization Quality of Life assessment instrument (WHOQOL-100).

Results

Before the treatment, there was no significant variance between the two groups in the JOA score and the 40-point rating method. Similarly, there was no significant difference in the levels of IL-1β, IL-1RA, and IL-8 between the two groups (p-value = 0.262, 0.387, and 0.154 respectively) prior to the treatment. Three months after the treatment, the levels of IL-1β and IL-8 in the observation group were 21.83 ±3.65 ng/l and 357.07 ±32.36 ng/l respectively, both lower than the control group value (p-value = 0.026, 0.028 respectively). The level of IL-1RA in follow-up was 21.59 ±1.15 ng/l, which was higher than that in the control group. Three months after the treatment, all the WHOQOL-100 parameters of the observation group for psychology, physiology, social relations, independence, spirituality, environment, and general quality of life were higher than those of the control group; the variance among the groups was statistically significant (p-value: <0.001).

Conclusions

The combination therapy with erythropoietin and methylprednisolone is effective for ischemia-reperfusion injuries of the spinal cord. It also reduces S-100β and NSE, inhibits IL-1β, and increases IL-8 and IL-1RA. Therefore, it preserves and improves spinal nerve function and the quality of life of patients.