The effect of high mobility group box-1 protein on cerebral edema, blood-brain barrier, oxidative stress and apoptosis in an experimental traumatic brain injury model

The effect of N-acetylcysteine on the neurotoxicity of sevoflurane in developing hippocampus cells

Sevoflurane, a common pediatric anesthetic, has been linked to neurodegeneration, raising safety concerns. This study explored N-acetylcysteine's protective potential against sevoflurane-induced neurotoxicity in rat hippocampi. Four groups were examined: Control: Received 6 hours of 3 l/min gas (air and 30 % O2) and intraperitoneal saline. NAC: Received 6 hours of 3 l/min gas and 150 mg/kg NAC intraperitoneally. Sev: Exposed to 6 hours of 3 l/min gas and 3 % sevoflurane. Sev+NAC: Received 6 hours of 3 l/min gas, 3 % sevoflurane, and 150 mg/kg NAC. Protein levels of NRF-2, NLRP3, IL-1β, caspase-1, Beclin 1, p62, LC3A, and apoptosis markers were assessed. Sevoflurane and NAC alone reduced autophagy, while Sev+NAC group maintained autophagy levels. Sev group had elevated NRF-2, NLRP3, pNRF2, Caspase-1, and IL-1β, which were reduced in Sev+NAC. Apoptosis was higher in Sev, but Sev+NAC showed reduced apoptosis compared to the control. In summary, sevoflurane induced neurotoxicity in developing hippocampus, which was mitigated by N-acetylcysteine administration.

Psychedelics for acquired brain injury: a review of molecular mechanisms and therapeutic potential

Acquired brain injury (ABI), such as traumatic brain injury and stroke, is a leading cause of disability worldwide, resulting in debilitating acute and chronic symptoms, as well as an increased risk of developing neurological and neurodegenerative disorders. These symptoms can stem from various neurophysiological insults, including neuroinflammation, oxidative stress, imbalances in neurotransmission, and impaired neuroplasticity. Despite advancements in medical technology and treatment interventions, managing ABI remains a significant challenge. Emerging evidence suggests that psychedelics may rapidly improve neurobehavioral outcomes in patients with various disorders that share physiological similarities with ABI. However, research specifically focussed on psychedelics for ABI is limited. This narrative literature review explores the neurochemical properties of psychedelics as a therapeutic intervention for ABI, with a focus on serotonin receptors, sigma-1 receptors, and neurotrophic signalling associated with neuroprotection, neuroplasticity, and neuroinflammation. The promotion of neuronal growth, cell survival, and anti-inflammatory properties exhibited by psychedelics strongly supports their potential benefit in managing ABI. Further research and translational efforts are required to elucidate their therapeutic mechanisms of action and to evaluate their effectiveness in treating the acute and chronic phases of ABI.

Serum biomarkers of hypoxic-ischemic brain injury

Brain injury is a multifaceted condition arising from nonspecific damage to nervous tissue. The resulting cognitive developmental impairments reverberate through patients' lives, affecting their families, and even the broader economic landscape. The significance of early brain injury detection lies in its potential to stave off severe consequences and enhance the effectiveness of tailored therapeutic interventions. While established methods like neuroimaging and neurophysiology serve as valuable diagnostic tools, their demanding nature restricts their accessibility, particularly in scenarios such as small hospitals, nocturnal or weekend shifts, and cases involving unstable patients. Hence, there is a pressing need for more accessible and efficient diagnostic avenues. Among the spectrum of brain injuries, hypoxic-ischemic encephalopathy stands out as a predominant affliction in the pediatric population. Diagnosing brain injuries in newborns presents challenges due to the subjective nature of assessments like Apgar scores and the inherent uncertainty in neurological examinations. In this context, methods like magnetic resonance and ultrasound hold recommendations for more accurate diagnosis. Recognizing the potential of serum biomarkers derived from blood samples, this paper underscores their promise as a more expedient and resource-efficient means of assessing brain injuries. The review compiles current insights into serum biomarkers, drawing from experiments conducted on animal models as well as human brain pathologies. The authors aim to elucidate specific characteristics, temporal profiles, and the available corpus of experimental and clinical data for serum biomarkers specific to brain injuries. These include neuron-specific enolase (NSE), ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), S100 calcium-binding protein beta (S100B), glial fibrillary acidic protein (GFAP), and high-mobility-group-protein-box-1 (HMGB1). This comprehensive endeavor contributes to advancing the understanding of brain injury diagnostics and potential avenues for therapeutic intervention.

Estrogenic regulation of claudin 5 and tight junction protein 1 gene expression in zebrafish: A role on blood-brain barrier?

The blood-brain barrier (BBB) is a physical interface between the blood and the brain parenchyma, playing key roles in brain homeostasis. In mammals, the BBB is established thanks to tight junctions between cerebral endothelial cells, involving claudin, occludin, and zonula occludens proteins. Estrogens have been documented to modulate BBB permeability. Interestingly, in the brain of zebrafish, the estrogen-synthesizing activity is strong due to the high expression of Aromatase B protein, encoded by the cyp19a1b gene, in radial glial cells (neural stem cells). Given the roles of estrogens in BBB function, we investigated their impact on the expression of genes involved in BBB tight junctions. We treated zebrafish embryos and adult males with 17β-estradiol and observed an increased cerebral expression of tight junction and claudin 5 genes in adult males only. In females, treatment with the nuclear estrogen receptor antagonist (ICI182,780 ) had no impact. Interestingly, telencephalic injuries performed in males decreased tight junction gene expression that was partially reversed with 17β-estradiol. This was further confirmed by extravasation experiments of Evans blue showing that estrogenic treatment limits BBB leakage. We also highlighted the intimate links between endothelial cells and neural stem cells, suggesting that cholesterol and peripheral steroids could be taken up by endothelial cells and used as precursors for estrogen synthesis by neural stem cells. Together, our results show that zebrafish provides an alternative model to further investigate the role of steroids on the expression of genes involved in BBB integrity, both in constitutive and regenerative physiological conditions. The link we described between capillaries endothelial cells and steroidogenic neural cells encourages the use of this model in understanding the mechanisms by which peripheral steroids get into neural tissue and modulate neurogenic activity.

Sesquiterpene nootkatone counteracted the melamine-induced neurotoxicity via repressing of oxidative stress, inflammatory, and apoptotic trajectories

Melamine (ML), a chemical substance of high nitrogen content, is used as a food adulterant. Former evidences implied that ML could induce a variety of toxic effects including neurotoxicity and cognitive impairment. Therefore, the aim of this study was to delineate the protective effect of the nootkatone (NK) against ML-induced neural adverse effects. Rats were orally pretreated with NK (5 and 10 mg/kg) prior to the oral administration of ML (700 mg/kg) for a period of 28 days. Our findings unveiled remarkable alleviating effect of NK on MK-induced neurobehavioral disturbance in open field test. Furthermore, NK lessened ML-caused increases in the acetylcholine esterase level in the brain tissue of exposed rats. NK also decreased the neural oxidative stress as represented by elevated levels of SOD, CAT, and GSH along with decreased MDA and NO levels. Upregulated mRNA expression levels of neural NRF-2 and HO-1 were noticed after NK administration. Remarkable anti-inflammatory impact was prominent by decreased neural IL-1β, and TNF-α along with downregulated NF-κB and TLR-4 gene expression levels in NK-treated rats. Noteworthily, pre-treatment with NK decreased the immune reaction of RAGE and HMGB-1 induced by oral ML exposure. Brain histological examination validated the obtained biochemical and molecular results. To sum up, these outcomes reveal that NK successfully alleviated the neural damage induced by ML via blocking of oxidative stress, and inflammatory signaling pathways. Consequently, our study may suggest NK as a new effective therapeutic supplement for treatment of ML-mediated neurotoxicity in rats via inhibition of HMGB-1-RAGE/TLR-4/NF-κB.

Circulating extracellular vesicles from patients with traumatic brain injury induce cerebrovascular endothelial dysfunction

Endothelial dysfunction is a key proponent of pathophysiological process of traumatic brain injury (TBI). We previously demonstrated that extracellular vesicles (EVs) released from injured brains led to endothelial barrier disruption and vascular leakage. However, the molecular mechanisms of this EV-induced endothelial dysfunction (endotheliopathy) remain unclear. Here, we enriched plasma EVs from TBI patients (TEVs), and detected high mobility group box 1 (HMGB1) exposure to 50.33 ± 10.17% of TEVs and the number of HMGB1⁺TEVs correlated with injury severity. We then investigated for the first time the impact of TEVs on endothelial function using adoptive transfer models. We found that TEVs induced dysfunction of cultured human umbilical vein endothelial cells and mediated endothelial dysfunction in both normal and TBI mice, which were propagated through the HMGB1-activated receptor for advanced glycation end products (RAGE)/Cathepsin B signaling, and the resultant NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome activation and canonical caspase-1/gasdermin D (GSDMD)-dependent pyroptosis. Finally, von Willebrand factor (VWF) was detected on the surface of 77.01 ± 7.51% of HMGB1⁺TEVs. The TEV-mediated endotheliopathy was reversed by a polyclonal VWF antibody, indicating that VWF might serve a coupling factor that tethered TEVs to ECs, thus facilitating HMGB1-induced endotheliopathy. These results suggest that circulating EVs isolated from patients with TBI alone are sufficient to induce endothelial dysfunction and contribute to secondary brain injury that are dependent on immunologically active HMGB1 exposed on their surface. This finding provided new insight for the development of potential therapeutic targets and diagnostic biomarkers for TBI.

The role of high mobility group box 1 in neuroinflammatory related diseases

High mobility group box 1 (HMGB1) is a ubiquitous and highly conserved non-histone DNA-binding protein with different biological functions according to its subcellular localization. It is widely believed that HMGB1, which is released into the extracellular space, plays a key role in the inflammatory response. In recent years, numerous studies have shown that the development of various neurological diseases such as epilepsy, Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), cerebrovascular disease and traumatic brain injury (TBI) are inextricably linked to inflammation. We will review the mechanisms of HMGB1 and its receptors in nervous system inflammation to provide a basis for further development of new HMGB1-based therapies.

A Focal Impact Model of Traumatic Brain Injury in Xenopus Tadpoles Reveals Behavioral Alterations, Neuroinflammation, and an Astroglial Response

Traumatic Brain Injury (TBI) is a global driver of disability, and we currently lack effective therapies to promote neural repair and recovery. TBI is characterized by an initial insult, followed by a secondary injury cascade, including inflammation, excitotoxicity, and glial cellular response. This cascade incorporates molecular mechanisms that represent potential targets of therapeutic intervention. In this study, we investigate the response to focal impact injury to the optic tectum of Xenopus laevis tadpoles. This injury disrupts the blood-brain barrier, causing edema, and produces deficits in visually-driven behaviors which are resolved within one week. Within 3 h, injured brains show a dramatic transcriptional activation of inflammatory cytokines, upregulation of genes associated with inflammation, and recruitment of microglia to the injury site and surrounding tissue. Shortly afterward, astrocytes undergo morphological alterations and accumulate near the injury site, and these changes persist for at least 48 h following injury. Genes associated with astrocyte reactivity and neuroprotective functions also show elevated levels of expression following injury. Since our results demonstrate that the response to focal impact injury in Xenopus resembles the cellular alterations observed in rodents and other mammalian models, the Xenopus tadpole offers a new, scalable vertebrate model for TBI.

Nonoxid-HMGB1 Attenuates Cognitive Impairment After Traumatic Brain Injury in Rats

Traumatic brain injury (TBI) is a major global burden of health. As an accepted inflammatory mediator, high mobility group box 1 (HMGB1) is found to be effective in facilitating neurogenesis and axonal regeneration. SH3RF2 (also known as POSHER), an E3 ligase SH3 domain-containing ring finger 2, belongs to the SH3RF family of proteins. Here, we aimed to investigate the role of redox states of HMGB1 on neurite outgrowth and regeneration both in vitro and in vivo. In this study, distinct recombinant HMGB1 redox isoforms were used. Sequencing for RNA-seq and data analysis were performed to find the potential downstream target of nonoxid-HMGB1 (3S-HMGB1). Protein changes and distribution of SH3RF2 were evaluated by western blot assays and immunofluorescence. Lentivirus and adeno-associated virus were used to regulate the expression of genes. Nonoxid-HMGB1-enriched exosomes were constructed and used to treat TBI rats. Neurological function was evaluated by OF test and NOR test. Results demonstrated that nonoxid-HMGB1 and fr-HMGB1, but not ds-HMGB1, promoted neurite outgrowth and axon elongation. RNA-seq and western blot assay indicated a significant increase of SH3RF2 in neurons after treated with nonoxid-HMGB1 or fr-HMGB1. Notably, the beneficial effects of nonoxid-HMGB1 were attenuated by downregulation of SH3RF2. Furthermore, nonoxid-HMGB1 ameliorated cognitive impairment in rats post-TBI via SH3RF2. Altogether, our experimental results suggest that one of the promoting neurite outgrowth and regeneration mechanisms of nonoxid-HMGB1 is mediated through the upregulated expression of SH3RF2. Nonoxid-HMGB1 is an attractive therapeutic candidate for the treatment of TBI.

Neural stem cell therapy in conjunction with curcumin loaded in niosomal nanoparticles enhanced recovery from traumatic brain injury

Despite a great amount of effort, there is still a need for reliable treatments of traumatic brain injury (TBI). Recently, stem cell therapy has emerged as a new avenue to address neuronal regeneration after TBI. However, the environment of TBI lesions exerts negative effects on the stem cells efficacy. Therefore, to maximize the beneficial effects of stem cells in the course of TBI, we evaluated the effect of human neural stem/progenitor cells (hNS/PCs) and curcumin-loaded niosome nanoparticles (CM-NPs) on behavioral changes, brain edema, gliosis, and inflammatory responses in a rat model of TBI. After TBI, hNS/PCs were transplanted within the injury site and CM-NPs were orally administered for 10 days. Finally, the effect of combination therapy was compared to several control groups. Our results indicated a significant improvement of general locomotor activity in the hNS/PCs + CM-NPs treatment group compared to the control groups. We also observed a significant improvement in brain edema in the hNS/PCs + CM-NPs treatment group compared to the other groups. Furthermore, a significant decrease in astrogliosis was seen in the combined treatment group. Moreover, TLR4-, NF-κB-, and TNF-α- positive cells were significantly decreased in hNS/PCs + CM-NPs group compared to the control groups. Taken together, this study indicated that combination therapy of stem cells with CM-NPs can be an effective therapy for TBI.

Microenvironmental Variations After Blood-Brain Barrier Breakdown in Traumatic Brain Injury

Traumatic brain injury (TBI) is linked to several pathologies. The blood-brain barrier (BBB) breakdown is considered to be one of the initial changes. Further, the microenvironmental alteration following TBI-induced BBB breakdown can be multi-scaled, constant, and dramatic. The microenvironmental variations after disruption of BBB includes several pathological changes, such as cerebral blood flow (CBF) alteration, brain edema, cerebral metabolism imbalances, and accumulation of inflammatory molecules. The modulation of the microenvironment presents attractive targets for TBI recovery, such as reducing toxic substances, inhibiting inflammation, and promoting neurogenesis. Herein, we briefly review the pathological alterations of the microenvironmental changes following BBB breakdown and outline potential interventions for TBI recovery based on microenvironmental modulation.

The Role of HMGB1 in Traumatic Brain Injury-Bridging the Gap Between the Laboratory and Clinical Studies

PURPOSE OF REVIEW

Traumatic brain injury (TBI) is amongst the leading causes of mortality and morbidity worldwide. However, several pharmacological strategies in the clinical setting remain unsuccessful. Mounting evidence implicates High Mobility Group Box protein 1 (HMGB1) as a unique alternative target following brain injury. Herein, we discuss current understanding of HMGB1 in TBI and obstacles to clinical translation.

RECENT FINDINGS

HMGB1 plays a pivotal role as a 'master-switch' of neuro-inflammation following injury and in the regulation of neurogenesis during normal development. Animal models point towards the involvement of HMGB1 signalling in prolonged activation of glial cells and widespread neuronal death. Early experimental studies demonstrate positive effects of HMGB1 antagonism on both immunohistochemical and neuro-behavioural parameters following injury. Raised serum/CSF HMGB1 in humans is associated with poor outcomes post-TBI. HMGB1 is a promising therapeutic target post-TBI. However, further studies elucidating receptor, cell, isoform, and temporal effects are required prior to clinical translation.

LPS Primes Brain Responsiveness to High Mobility Group Box-1 Protein

High mobility group box (HMGB)1 action contributes to late phases of sepsis, but the effects of increased endogenous plasma HMGB1 levels on brain cells during inflammation are unclear. Here, we aimed to further investigate the role of HMGB1 in the brain during septic-like lipopolysaccharide-induced inflammation in rats (LPS, 10 mg/kg, i.p.). HMGB-1 mRNA expression and release were measured in the periphery/brain by RT-PCR, immunohistochemistry and ELISA. In vitro experiments with disulfide-HMGB1 in primary neuro-glial cell cultures of the area postrema (AP), a circumventricular organ with a leaky blood–brain barrier and direct access to circulating mediators like HMGB1 and LPS, were performed to determine the direct influence of HMGB1 on this pivotal brain structure for immune-to-brain communication. Indeed, HMGB1 plasma levels stayed elevated after LPS injection. Immunohistochemistry of brains and AP cultures confirmed LPS-stimulated cytoplasmatic translocation of HMGB1 indicative of local HMGB1 release. Moreover, disulfide-HMGB1 stimulation induced nuclear factor (NF)-κB activation and a significant release of interleukin-6, but not tumor necrosis factor α, into AP culture supernatants. However, only a few AP cells directly responded to HMGB1 with increased intracellular calcium concentration. Interestingly, priming with LPS induced a seven-fold higher percentage of responsive cells to HMGB1. We conclude that, as a humoral and local mediator, HMGB1 enhances brain inflammatory responses, after LPS priming, linked to sustained sepsis symptoms.

Hydroxysafflor yellow A acutely attenuates blood-brain barrier permeability, oxidative stress, inflammation and apoptosis in traumatic brain injury in rats1

Purpose:

To investigate the therapeutic benefits of Hydroxysafflor yellow A (HSYA) on blood-brain barrier (BBB) vulnerability after traumatic brain injury (TBI) and identify its potential action of mechanisms on TBIinduced injuries.

Methods:

The rat TBI model was performed by using a controlled cortical impact device. The BBB permeability induced by TBI was measured through Evans Blue dye superflux and western blotting or polymerase chain reaction (PCR) for tight junctional proteins (TJPs). The post-TBI changes in oxidative stress markers, inflammatory response and neuron apoptosis in brain tissue were also tested.

Results:

Herein, the results showed that HSYA acutely attenuated BBB permeability via increasing the production of the TJPs, including occludin, claudin-1 and zonula occludens protein 24 h after TBI. Additionally, HSYA could suppress the secretion of proinflammatory factors, such as interleukin-1β, interleukin-6, and tumor necrosis factor-α (IL-1β, IL-6, and TNF-α), and also concurrently down-regulate the expression of inflammation-related Toll-like receptor 4/nuclear factor kappa-B (TLR4/NF-kB) protein. These HSYA challenged changes were accompanied by the decreased TBI induced oxidative stress markers and inhibited the expression of apoptosis proteins Bax, caspase-3 and caspase-9.

Conclusions:

Taken together, all findings suggested that HSYA (30 mg/kg) are against TBI through improving the integrity in BBB, which are associated with the antioxidant, anti-inflammation and antiapoptosis via the probable mechanism of down-regulation of the TLR4/NF-kB pathway, and its in-detail protective mechanisms are under study.

Extracellular Vesicle-Derived microRNA-410 From Mesenchymal Stem Cells Protects Against Neonatal Hypoxia-Ischemia Brain Damage Through an HDAC1-Dependent EGR2/Bcl2 Axis

Hypoxia-ischemia brain damage (HIBD) is a neurological disorder occring in neonates, which is exacerbated by neuronal apoptosis. Mesenchymal stem cells (MSCs)-derived extracellular vesicles (EVs) have been proposed as a promising strategy for treating or preventing ischemia-related diseases. However, their mechanisms in HIBD remain unclear. Thus, we aimed to address the role of EV-derived microRNA (miR)-410 in HIBD. Neonatal HIBD mouse model was constructed using HI insult, from which neurons were isolated, followed by exposure to oxygen glucose deprivation (OGD). EVs were isolated from human umbilical cord (hUC)-derived MSCs. In silico analyses, dual-luciferase reporter gene and chromatin immunoprecipitation assays were adopted to determine relationships among miR-410, histone deacetylase 1 (HDAC1), early growth response protein 2 (EGR2), and B cell lymphoma/leukemia 2 (Bcl2). The functional roles of EV-derived miR-410 were determined using loss- and gain-of functions experiments, and by evaluating neuronal viability, cell-cycle distribution and neuronal apoptosis in vitro as well as modified neurological severity score (mNSS), edema formation, and cerebral infarction volume in vivo. hUC-MSCs-derived EVs protected against HIBD in vivo and inhibited the OGD-induced neuronal apoptosis in vitro. miR-410 was successfully delivered to neurons by hUC-MSCs-EVs and negatively targeted HDAC1, which inversely mediated the expression of EGR2/Bcl2. Upregulation of EV-derived miR-410 promoted the viability but inhibited apoptosis of neurons, which was reversed by HDAC1 overexpression. EV-derived miR-410 elevation reduced mNSS, edema formation, and cerebral infarction volume by increasing EGR2/Bcl2 expression through downregulating HDAC1 expression in vivo. In summary, EV-derived miR-410 impeded neuronal apoptosis by elevating the expression of EGR2/Bcl2 via HDAC1 downregulation, thereby providing a potential strategy for treating or preventing HIBD.

Neurogenesis after traumatic brain injury - The complex role of HMGB1 and neuroinflammation

INTRODUCTION

Traumatic brain injury (TBI) is amongst the leading causes of morbidity and mortality worldwide. Despite evidence of neurogenesis post-TBI, survival and integration of newborn neurons remains impaired. High Mobility Group Box protein 1 (HMGB1) is an 'alarmin' released hyper-acutely following TBI and implicated in hosting the neuro-inflammatory response to injury. It is also instrumental in mediating neurogenesis under physiological conditions. Given its dual role in mediating neuro-inflammation and neurogenesis, it serves as a promising putative target for therapeutic modulation. In this review, we discuss neurogenesis post-TBI, neuro-pharmacological aspects of HMGB1, and its potential as a therapeutic target.

METHODS

PubMed database was searched with varying combinations of the following search terms: HMGB1, isoforms, neurogenesis, traumatic brain injury, Toll-like receptor (TLR), receptor for advanced glycation end-products (RAGE).

RESULTS

Several in vitro and in vivo studies demonstrate evidence of neurogenesis post-injury. The HMGB1-RAGE axis mediates neurogenesis throughout development, whilst interaction with TLR-4 promotes the innate immune response. Studies in the context of injury demonstrate that these receptor effects are not mutually exclusive. Despite recognition of different HMGB1 isoforms based on redox/acetylation status, effects on neurogenesis post-injury remain unexplored. Recent animal in vivo studies examining HMGB1 antagonism post-TBI demonstrate predominantly positive results, but specific effects on neurogenesis and longer-term outcomes remain unclear.

CONCLUSION

HMGB1 is a promising therapeutic target but its effects on neurogenesis post-TBI remains unclear. Given the failure of several pharmacological strategies to improve outcomes following TBI, accurate delineation of HMGB1 signalling pathways and effects on post-injury neurogenesis are vital.

HMGB1-Mediated Neuroinflammatory Responses in Brain Injuries: Potential Mechanisms and Therapeutic Opportunities

Brain injuries are devastating conditions, representing a global cause of mortality and morbidity, with no effective treatment to date. Increased evidence supports the role of neuroinflammation in driving several forms of brain injuries. High mobility group box 1 (HMGB1) protein is a pro-inflammatory-like cytokine with an initiator role in neuroinflammation that has been implicated in Traumatic brain injury (TBI) as well as in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Herein, we discuss the implication of HMGB1-induced neuroinflammatory responses in these brain injuries, mediated through binding to the receptor for advanced glycation end products (RAGE), toll-like receptor4 (TLR4) and other inflammatory mediators. Moreover, we provide evidence on the biomarker potential of HMGB1 and the significance of its nucleocytoplasmic translocation during brain injuries along with the promising neuroprotective effects observed upon HMGB1 inhibition/neutralization in TBI and EBI induced by SAH. Overall, this review addresses the current advances on neuroinflammation driven by HMGB1 in brain injuries indicating a future treatment opportunity that may overcome current therapeutic gaps.