Laminin as a Biomarker of Blood-Brain Barrier Disruption under Neuroinflammation: A Systematic Review

LAMC1 attenuates neuronal apoptosis via FAK/PI3K/AKT signaling pathway after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

The poor prognosis in patients with subarachnoid hemorrhage (SAH) is often attributed to neuronal apoptosis. Recent evidence suggests that Laminin subunit gamma 1 (LAMC1) is essential for cell survival and proliferation. However, the effects of LAMC1 on early brain injury after SAH and the underlying mechanisms are unknown. The current study aimed to reveal the anti-neuronal apoptotic effect and the potential mechanism of LAMC1 in the rat and in the in vitro SAH models.

METHODS

The SAH model of Sprague-Dawley rats was established by endovascular perforation. Recombinant LAMC1 (rLAMC1) was administered intranasally 30 min after modeling. LAMC1 small interfering RNA (LAMC1 siRNA), focal adhesion kinase (FAK)-specific inhibitor Y15 and PI3K-specific inhibitor LY294002 were administered before SAH modeling to explore the neuroprotection mechanism of rLAMC1. HT22 cells were cultured and stimulated by oxyhemoglobin to establish an in vitro model of SAH. Subsequently, SAH grades, neurobehavioral tests, brain water content, blood-brain barrier permeability, western blotting, immunofluorescence, TUNEL, and Fluoro-Jade C staining were performed.

RESULTS

The expression of endogenous LAMC1 was markedly decreased after SAH, both in vitro and in vivo. rLAMC1 significantly reduced the brain water content and blood-brain barrier permeability, improved short- and long-term neurobehavior, and decreased neuronal apoptosis. Furthermore, rLAMC1 treatment significantly increased the expression of p-FAK, p-PI3K, p-AKT, Bcl-XL, and Bcl-2 and decreased the expression of Bax and cleaved caspase -3. Conversely, knockdown of endogenous LAMC1 aggravated the neurological impairment, suppressed the expression of Bcl-XL and Bcl-2, and upregulated the expression of Bax and cleaved caspase-3. Additionally, the administration of Y15 and LY294002 abolished the protective roles of rLAMC1. In vitro, rLAMC1 significantly reduced neuronal apoptosis, and the protective effects were also abolished by Y15 and LY294002.

CONCLUSION

Exogenous LAMC1 treatment improved neurological deficits after SAH in rats, and attenuated neuronal apoptosis in both in vitro and in vivo SAH models, at least partially through the FAK/PI3K/AKT pathway.

Blood-brain barrier biomarkers

The blood-brain barrier (BBB) is a dynamic interface that regulates the exchange of molecules and cells between the brain parenchyma and the peripheral blood. The BBB is mainly composed of endothelial cells, astrocytes and pericytes. The integrity of this structure is essential for maintaining brain and spinal cord homeostasis and protection from injury or disease. However, in various neurological disorders, such as traumatic brain injury, Alzheimer's disease, and multiple sclerosis, the BBB can become compromised thus allowing passage of molecules and cells in and out of the central nervous system parenchyma. These agents, however, can serve as biomarkers of BBB permeability and neuronal damage, and provide valuable information for diagnosis, prognosis and treatment. Herein, we provide an overview of the BBB and changes due to aging, and summarize current knowledge on biomarkers of BBB disruption and neurodegeneration, including permeability, cellular, molecular and imaging biomarkers. We also discuss the challenges and opportunities for developing a biomarker toolkit that can reliably assess the BBB in physiologic and pathophysiologic states.

Specific nanoprobe design for MRI: Targeting laminin in the blood-brain barrier to follow alteration due to neuroinflammation

Chronic neuroinflammation is characterized by increased blood-brain barrier (BBB) permeability, leading to molecular changes in the central nervous system that can be explored with biomarkers of active neuroinflammatory processes. Magnetic resonance imaging (MRI) has contributed to detecting lesions and permeability of the BBB. Ultra-small superparamagnetic particles of iron oxide (USPIO) are used as contrast agents to improve MRI observations. Therefore, we validate the interaction of peptide-88 with laminin, vectorized on USPIO, to explore BBB molecular alterations occurring during neuroinflammation as a potential tool for use in MRI. The specific labeling of NPS-P88 was verified in endothelial cells (hCMEC/D3) and astrocytes (T98G) under inflammation induced by interleukin 1β (IL-1β) for 3 and 24 hours. IL-1β for 3 hours in hCMEC/D3 cells increased their co-localization with NPS-P88, compared with controls. At 24 hours, no significant differences were observed between groups. In T98G cells, NPS-P88 showed similar nonspecific labeling among treatments. These results indicate that NPS-P88 has a higher affinity towards brain endothelial cells than astrocytes under inflammation. This affinity decreases over time with reduced laminin expression. In vivo results suggest that following a 30-minute post-injection, there is an increased presence of NPS-P88 in the blood and brain, diminishing over time. Lastly, EAE animals displayed a significant accumulation of NPS-P88 in MRI, primarily in the cortex, attributed to inflammation and disruption of the BBB. Altogether, these results revealed NPS-P88 as a biomarker to evaluate changes in the BBB due to neuroinflammation by MRI in biological models targeting laminin.

Building a pathway to recovery: Targeting ECM remodeling in CNS injuries

Extracellular matrix (ECM) is a complex and dynamic network of proteoglycans, proteins, and other macromolecules that surrounds cells in tissues. The ECM provides structural support to cells and plays a critical role in regulating various cellular functions. ECM remodeling is a dynamic process involving the breakdown and reconstruction of the ECM. This process occurs naturally during tissue growth, wound healing, and tissue repair. However, in the context of central nervous system (CNS) injuries, dysregulated ECM remodeling can lead to the formation of fibrotic and glial scars. CNS injuries encompass various traumatic events, including concussions and fractures. Following CNS trauma, the formation of glial and fibrotic scars becomes prominent. Glial scars primarily consist of reactive astrocytes, while fibrotic scars are characterized by an abundance of ECM proteins. ECM remodeling plays a pivotal and tightly regulated role in the development of these scars after spinal cord and brain injuries. Various factors like ECM components, ECM remodeling enzymes, cell surface receptors of ECM molecules, and downstream pathways of ECM molecules are responsible for the remodeling of the ECM. The aim of this review article is to explore the changes in ECM during normal physiological conditions and following CNS injuries. Additionally, we discuss various approaches that target various factors responsible for ECM remodeling, with a focus on promoting axon regeneration and functional recovery after CNS injuries. By targeting ECM remodeling, it may be possible to enhance axonal regeneration and facilitate functional recovery after CNS injuries.

Inter-Alpha Inhibitor Proteins Modify the Microvasculature after Exposure to Hypoxia-Ischemia and Hypoxia in Neonatal Rats

Microvasculature develops during early brain development. Hypoxia-ischemia (HI) and hypoxia (H) predispose to brain injury in neonates. Inter-alpha inhibitor proteins (IAIPs) attenuate injury to the neonatal brain after exposure to HI. However, the effects of IAIPs on the brain microvasculature after exposure to HI have not been examined in neonates. Postnatal day-7 rats were exposed to sham treatment or right carotid artery ligation and 8% oxygen for 90 min. HI comprises hypoxia (H) and ischemia to the right hemisphere (HI-right) and hypoxia to the whole body, including the left hemisphere (H-left). Human IAIPs (hIAIPs, 30 mg/kg) or placebo were injected immediately, 24 and 48 h after HI/H. The brains were analyzed 72 h after HI/H to determine the effects of hIAIPs on the microvasculature by laminin immunohistochemistry and calculation of (1) the percentage area stained by laminin, (2) cumulative microvessel length, and (3) density of tunneling nanotubes (TNTs), which are sensitive indicators of the earliest phases of neo-vascularization/collateralization. hIAIPs mainly affected the percent of the laminin-stained area after HI/H, cumulative vessel length after H but not HI, and TNT density in females but not males. hIAIPs modify the effects of HI/H on the microvasculature after brain injury in neonatal rats and exhibit sex-related differential effects. Our findings suggest that treatment with hIAIPs after exposure to H and HI in neonatal rats affects the laminin content of the vessel basal lamina and angiogenic responses in a sex-related fashion.

Time Dependent Changes in the Ovine Neurovascular Unit; A Potential Neuroprotective Role of Annexin A1 in Neonatal Hypoxic-Ischemic Encephalopathy

Perinatal brain injury following hypoxia-ischemia (HI) is characterized by high mortality rates and long-term disabilities. Previously, we demonstrated that depletion of Annexin A1, an essential mediator in BBB integrity, was associated with a temporal loss of blood-brain barrier (BBB) integrity after HI. Since the molecular and cellular mechanisms mediating the impact of HI are not fully scrutinized, we aimed to gain mechanistic insight into the dynamics of essential BBB structures following global HI in relation to ANXA1 expression. Global HI was induced in instrumented preterm ovine fetuses by transient umbilical cord occlusion (UCO) or sham occlusion (control). BBB structures were assessed at 1, 3, or 7 days post-UCO by immunohistochemical analyses of ANXA1, laminin, collagen type IV, and PDGFRβ for pericytes. Our study revealed that within 24 h after HI, cerebrovascular ANXA1 was depleted, which was followed by depletion of laminin and collagen type IV 3 days after HI. Seven days post-HI, increased pericyte coverage, laminin and collagen type IV expression were detected, indicating vascular remodeling. Our data demonstrate novel mechanistic insights into the loss of BBB integrity after HI, and effective strategies to restore BBB integrity should potentially be applied within 48 h after HI. ANXA1 has great therapeutic potential to target HI-driven brain injury.

Rapid and Stable Formation Method of Human Astrocyte Spheroid in a High Viscous Methylcellulose Medium and Its Functional Advantages

Astrocytes, a type of glial cell in the brain, are thought to be functionally and morphologically diverse cells that regulate brain homeostasis. Cell immortalization is a promising technique for the propagation of primary human astrocytes. The immortalized cells retain their astrocytic marker mRNA expression at lower levels than the primary cells. Therefore, improvement of the differentiation status is required. The use of a 3D formation technique to mimic structural tissue is a good strategy for reflecting physiological cell–cell interactions. Previously, we developed a spheroid formation method using highly viscous methyl cellulose (MC) medium. In this study, we applied this formation method to the well-established immortalized human astrocyte cell line HASTR/ci35. Stable HASTR/ci35 spheroids were successfully formed in MC medium, and laminin deposition was detected inside of the spheroids. Their functional markers were enhanced compared to conventional spheroids formed in U-bottom plates. The inflammatory response was moderately sensitive, and the ability to support neurite growth was confirmed. The HASTR/ci35 spheroid in the MC medium demonstrated the differentiation phenotype and could serve as a potent in vitro model for matured astrocytes.

Astrocytes as a Therapeutic Target in Alzheimer's Disease-Comprehensive Review and Recent Developments

Alzheimer's disease (AD) is a frequent and disabling neurodegenerative disorder, in which astrocytes participate in several pathophysiological processes including neuroinflammation, excitotoxicity, oxidative stress and lipid metabolism (along with a critical role in apolipoprotein E function). Current evidence shows that astrocytes have both neuroprotective and neurotoxic effects depending on the disease stage and microenvironmental factors. Furthermore, astrocytes appear to be affected by the presence of amyloid-beta (Aβ), with alterations in calcium levels, gliotransmission and proinflammatory activity via RAGE-NF-κB pathway. In addition, astrocytes play an important role in the metabolism of tau and clearance of Aβ through the glymphatic system. In this review, we will discuss novel pharmacological and non-pharmacological treatments focused on astrocytes as therapeutic targets for AD. These interventions include effects on anti-inflammatory/antioxidant systems, glutamate activity, lipid metabolism, neurovascular coupling and glymphatic system, calcium dysregulation, and in the release of peptides which affects glial and neuronal function. According to the AD stage, these therapies may be of benefit in either preventing or delaying the progression of the disease.

Beneficial effects of natural flavonoids on neuroinflammation

Neuroinflammation is the fundamental immune response against multiple factors in the central nervous system and is characterized by the production of inflammatory mediators, activated microglia and astrocytes, and the recruitment of innate and adaptive immune cells to inflammatory sites, that contributes to the pathological process of related brain diseases, such as Alzheimer’s disease, Parkinson’s disease, depression, and stroke. Flavonoids, as a species of important natural compounds, have been widely revealed to alleviate neuroinflammation by inhibiting the production of pro-inflammatory mediators, elevating the secretion of anti-inflammatory factors, and modulating the polarization of microglia and astrocyte, mainly via suppressing the activation of NLRP3 inflammasome, as well as NF-κB, MAPK, and JAK/STAT pathways, promoting Nrf2, AMPK, BDNF/CREB, Wnt/β-Catenin, PI3k/Akt signals and SIRT1-mediated HMGB1 deacetylation. This review will provide the latest and comprehensive knowledge on the therapeutic benefits and mechanisms of natural flavonoids in neuroinflammation, and the natural flavonoids might be developed into food supplements or lead compounds for neuroinflammation-associated brain disorders.

Crotalphine Modulates Microglia M1/M2 Phenotypes and Induces Spinal Analgesia Mediated by Opioid-Cannabinoid Systems

Pain is a worldwide public health problem and its treatment is still a challenge since clinically available drugs do not completely reverse chronic painful states or induce undesirable effects. Crotalphine is a 14 amino acids synthetic peptide that induces a potent and long-lasting analgesic effect on acute and chronic pain models, peripherally mediated by the endogenous release of dynorphin A and the desensitization of the transient receptor potential ankyrin 1 (TRPA1) receptor. However, the effects of crotalphine on the central nervous system (CNS) and the signaling pathway have not been investigated. Thus, the central effect of crotalphine was evaluated on the partial sciatic nerve ligation (PSNL)-induced chronic neuropathic pain model. Crotalphine (100 µg/kg, p.o.)-induced analgesia on the 14th day after surgery lasting up to 24 h after administration. This effect was prevented by intrathecal administration of CB1 (AM251) or CB2 (AM630) cannabinoid receptor antagonists. Besides that, crotalphine-induced analgesia was reversed by CTOP, nor-BNI, and naltrindole, antagonists of mu, kappa, and delta-opioid receptors, respectively, and also by the specific antibodies for β-endorphin, dynorphin-A, and met-enkephalin. Likewise, the analgesic effect of crotalphine was blocked by the intrathecal administration of minocycline, an inhibitor of microglial activation and proliferation. Additionally, crotalphine decreased the PSNL-induced IL-6 release in the spinal cord. Importantly, in vitro, crotalphine inhibited LPS-induced CD86 expression and upregulated CD206 expression in BV-2 cells, demonstrating a polarization of microglial cells towards the M2 phenotype. These results demonstrated that crotalphine, besides activating opioid and cannabinoid analgesic systems, impairs central neuroinflammation, confirming the neuromodulatory mechanism involved in the crotalphine analgesic effect.