Breakdown Of Blood-nerve Barrier Research Articles

Selective blood-nerve barrier leakiness with claudin-1 and vessel-associated macrophage loss in diabetic polyneuropathy

Diabetic polyneuropathy (DPN) is the most common complication in diabetes and can be painful in up to 26% of all diabetic patients. Peripheral nerves are shielded by the blood-nerve barrier (BNB) consisting of the perineurium and endoneurial vessels. So far, there are conflicting results regarding the role and function of the BNB in the pathophysiology of DPN. In this study, we analyzed the spatiotemporal tight junction protein profile, barrier permeability, and vessel-associated macrophages in Wistar rats with streptozotocin-induced DPN. In these rats, mechanical hypersensitivity developed after 2 weeks and loss of motor function after 8 weeks, while the BNB and the blood-DRG barrier were leakier for small, but not for large molecules after 8 weeks only. The blood-spinal cord barrier remained sealed throughout the observation period. No gross changes in tight junction protein or cytokine expression were observed in all barriers to blood. However, expression of Cldn1 mRNA in perineurium was specifically downregulated in conjunction with weaker vessel-associated macrophage shielding of the BNB. Our results underline the role of specific tight junction proteins and BNB breakdown in DPN maintenance and differentiate DPN from traumatic nerve injury. Targeting claudins and sealing the BNB could stabilize pain and prevent further nerve damage.Key messages• In diabetic painful neuropathy in rats:• Blood nerve barrier and blood DRG barrier are leaky for micromolecules.• Perineurial Cldn1 sealing the blood nerve barrier is specifically downregulated.• Endoneurial vessel-associated macrophages are also decreased.• These changes occur after onset of hyperalgesia thereby maintaining rather than inducing pain.Graphical abstract

Different distribution of demyelination in chronic inflammatory demyelinating polyneuropathy subtypes

In demyelinating polyneuropathies, distribution patterns of demyelination reflect underlying pathogenesis. Median and ulnar nerve conduction studies were reviewed in 85 typical chronic inflammatory demyelinating polyneuropathy (CIDP) patients and 29 multifocal acquired demyelinating sensory and motor neuropathy (MADSAM). Distal latencies were prolonged in typical CIDP and near normal in MADSAM. Abnormal amplitude reductions in the nerve trunks were more frequent in MADSAM than typical CIDP. Presumably because the blood-nerve barrier is anatomically deficient at the distal nerve terminals, antibody-mediated demyelination is a major pathophysiology in typical CIDP. In contrast, blood-nerve barrier breakdown is likely to be predominant in MADSAM.

Regional Differences in Tight Junction Protein Expression in the Blood-DRG Barrier and Their Alterations after Nerve Traumatic Injury in Rats.

The nervous system is shielded by special barriers. Nerve injury results in blood–nerve barrier breakdown with downregulation of certain tight junction proteins accompanying the painful neuropathic phenotype. The dorsal root ganglion (DRG) consists of a neuron-rich region (NRR, somata of somatosensory and nociceptive neurons) and a fibre-rich region (FRR), and their putative epi-/perineurium (EPN). Here, we analysed blood–DRG barrier (BDB) properties in these physiologically distinct regions in Wistar rats after chronic constriction injury (CCI). Cldn5, Cldn12, and Tjp1 (rats) mRNA were downregulated 1 week after traumatic nerve injury. Claudin-1 immunoreactivity (IR) found in the EPN, claudin-19-IR in the FRR, and ZO-1-IR in FRR-EPN were unaltered after CCI. However, laser-assisted, vessel specific qPCR, and IR studies confirmed a significant loss of claudin-5 in the NRR. The NRR was three-times more permeable compared to the FRR for high and low molecular weight markers. NRR permeability was not further increased 1-week after CCI, but significantly more CD68+ macrophages had migrated into the NRR. In summary, NRR and FRR are different in naïve rats. Short-term traumatic nerve injury leaves the already highly permeable BDB in the NRR unaltered for small and large molecules. Claudin-5 is downregulated in the NRR. This could facilitate macrophage invasion, and thereby neuronal sensitisation and hyperalgesia. Targeting the stabilisation of claudin-5 in microvessels and the BDB barrier could be a future approach for neuropathic pain therapy.

Can we assess severity of Guillain-Barré syndrome using absolute monocyte count?

Guillain-Barré syndrome (GBS) is an inflammatory demyelinating autoimmune disease, associated with blood-nerve barrier breakdown, inflammatory cells infiltration, and cytokine leakage in the peripheral nervous system. Currently, it has been revealed that monocytes play key roles in the inflammatory response. Therefore, we aimed to assess the correlation between monocyte count and GBS in this study. Retrospective study was conducted in 114 patients with GBS and 120 age- and gender-matched individuals. Absolute monocyte count in patients with GBS was higher than that in healthy controls (0.61±0.24 vs 0.41±0.10; P <.001). Interestingly, monocyte count had significant positive correlations with CRP, ESR, and disease severity of GBS (r=.244, P=.009; r=.269, P=.004; r=.322, P<.001). A cutoff value of 0.515 for monocyte count was observed in patients with GBS (areas under the curve=0.808, 95% confidence interval=0.749-0.868, P <.001). Meanwhile, absolute monocyte count was independently associated with GBS in logistic regression analysis (odds ratio=2.291, 95% confidence interval=3.557-27.493, P<.001). Our findings demonstrated that elevated monocyte count is independently associated with GBS patients, and suggested monocyte count is positively associated with disease severity of GBS.

Severity and Patterns of Blood-Nerve Barrier Breakdown in Patients with Chronic Inflammatory Demyelinating Polyradiculoneuropathy: Correlations with Clinical Subtypes

ObjectiveChronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is currently classified into clinical subtypes, including typical and atypical forms (multifocal acquired demyelinating sensory and motor neuropathy (MADSAM) and distal acquired demyelinating symmetric neuropathy (DADS)). The aim of this study was to elucidate the patterns and severity of breakdown of the blood-nerve barrier (BNB) in each CIDP subtype.MethodsWe evaluated the effects of sera obtained from patients with typical CIDP, MADSAM and DADS and control subjects on the expression levels of tight junction proteins and transendothelial electrical resistance (TEER) value in human peripheral nerve microvascular endothelial cells (PnMECs).ResultsThe sera obtained from the patients with the three clinical phenotypes of CIDP decreased the amount of claudin-5 protein levels and TEER values in the PnMECs. In addition, the sera obtained from typical CIDP patients more prominently reduced claudin-5 protein levels and TEER values in the PnMECs than did that obtained from the MADSAM and DADS patients. Furthermore, the severity of BNB disruption after exposure to the sera was associated with higher Hughes grade, lower MRC score, more pronounced slowing of motor nerve conduction in the median nerve and higher frequency of abnormal temporal dispersion.ConclusionsSera derived from typical CIDP patients destroy the BNB more severely than those from MADSAM or DADS patients. The extent of BNB disruption in the setting of CIDP is associated with clinical disability and demyelination in the nerve trunk. These observations may explain the phenotypical differences between CIDP subtypes.

血液神経関門と糖尿病性ニューロパチー －糖尿病性ニューロパチーでは血液神経関門が破綻する－

血液神経関門と糖尿病性ニューロパチー －糖尿病性ニューロパチーでは血液神経関門が破綻する－

Pathogenesis of chronic inflammatory demyelinating polyradiculoneuropathy.

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a term applied to a spectrum of immune-mediated demyelinating neuropathies that are heterogeneous in clinical manifestations and probably in pathogenesis. Although histopathologic studies of CIDP have been complicated by a relapsing course of the inflammatory reaction and its predominance in proximal nerve segments, many clues point to involvement of both cellular and humoral immune factors in the pathogenesis. Uncertainties remain regarding the provoking antigen(s) and location of the initial T cell activation. Breakdown of blood nerve barrier by activated T cells and its cytokines is followed by a local intraneural immune response with recruitment of macrophages and secretion of toxic factors, which cause damage to the myelin and axons. Activated T cells may also induce B cells to produce antibodies against nerve/myelin antigens. This review summarizes our current knowledge of the immunopathogenesis and insight from animal models of CIDP.

Endothelial cell loss in irradiated optic nerves

ObjectiveRadiation optic neuropathy usually occurs months to years after exposure of the anterior visual pathways to ionizing radiation. It is characterized by high signal on gadolinium-enhanced T1-weighted magnetic resonance imaging. Radiation-induced endothelial cell damage resulting in blood-nerve barrier breakdown is hypothesized to produce this pattern, but histologic evidence of this in the optic nerve is lacking. We attempted to evaluate the effect of radiation on endothelial cells in the optic nerve. DesignCase-controlled histologic study. MethodsWe studied the optic nerves of 16 enucleated eyes from patients with uveal melanoma treated with proton beam irradiation, 6 from normal eyes and 5 from eyes with unirradiated uveal melanomas. Binding of Ulex europaeus agglutinin I (UEA-I) lectin was used to identify endothelial cells in single paraffin sections. Transverse and longitudinal sections of vessels were counted in masked fashion. ResultsThere were 49.4 ± 6.9 transversely sectioned endothelial cells per millimeter of nerve in 6 optic nerves exposed to 0 to 1000 cGyE (“low-dose”) compared with 17.3 ± 5.3 in 10 nerves exposed to 5500 to 7000 cGyE (“high-dose”) (P = 0.002). Longitudinally sectioned vessels stained with UEA-I were separately identified, with 11.5 ± 2.1 in the low-dose group and 5.6 ± 1.6 in the high-dose group (P = 0.044). The thickness and staining of the endothelial cell layer appeared greater in the high-dose group. Endothelial cell counts did not correlate with age, gender, acuity, or interval after irradiation. ConclusionsIncreased radiation dosage to the optic nerve correlates with smaller numbers of endothelial cells.

Restimulation of Resting Autoreactive T Cells by Schwann Cells in Vitro

This study demonstrates that rat Schwann cells can reactivate resting experimental allergic neuritis generating P2 and P2 peptide specific CD4+ T cell lines. T cell proliferation was significantly greater to P2 than to P2 peptide (SP-26) or ovalbumin (OA). Four-level analysis of variance showed that T cell proliferation with endogenous or exogenous P2 was not significantly different for Schwann cells plus cytokine IFN-γ (P = 0.5071) unlike P2 peptide or OA specific T cells (P = 0.0056 and 0.0003, respectively). Untreated Schwann cells were more effective inducers than irradiated or fixed Schwann cells. As stimulated CD4+ P2 T cells produce IFN-γ and TNF-α, this could exacerbate blood nerve barrier breakdown that has been increasingly implicated in inflammatory demyelinating neuropathies (IDNs). This would permit entry of antibodies and complement, thereby contributing to the demyelination process. Schwann cell induced reactivation of CD4+ T cells may therefore play a role in IDNs.

Matrix metalloproteinases in inflammatory demyelination: targets for treatment.

Matrix metalloproteinases (MMPs) degrade all protein components of the extracellular matrix. Functionally, they contribute to several different physiologic conditions, such as angiogenesis or bone remodeling, as well as pathologic conditions in humans, such as rheumatoid arthritis and tumor growth. MMPs seem to be important in the pathogenesis of inflammatory demyelinating diseases of the central and peripheral nervous system, especially in MS and in Guillain-Barré syndrome (GBS). Key mechanisms in the genesis of inflammatory demyelination, such as leukocyte recruitment, blood-brain barrier or blood-nerve barrier breakdown, myelin destruction, and release of disease-promoting cytokines, are considered to be MMP-dependent processes. In experimental autoimmune encephalomyelitis, an animal model of MS, and experimental autoimmune neuritis, an animal model of GBS, different synthetic inhibitors targeting MMP activity are able to suppress and even reverse ongoing disease. This evidence points to MMPs as new targets for treatment in inflammatory demyelination.

Nerve Crush Injuries—A Model for Axonotmesis

Nerve crush is a commonly used experimental model in the rat; however, a standard method of inducing this injury has not been defined. This study examined six crush techniques that are frequently used and characterized the subsequent nerve injury. Five types of nerve crush using a No. 5 jeweler's forceps and a sixth using a 30-s single crush with a serrated hemostat were studied in the posterior tibial nerve of the Lewis rat. Regeneration was evaluated using serial walking track assessments at 1, 2, 4, 6, and 8 weeks postoperatively. Nerve conduction studies and histological examination were performed at 2 days, 2 weeks, and 8 weeks. Blood-nerve barrier breakdown was observed at 2 days and recovered by 2 weeks. By 4 weeks normal walking track patterns were obtained in all groups. A pattern of Wallerian degeneration and axonal regeneration was noted at 2 weeks, with histological recovery in all groups by 8 weeks. Nerve crush, induced by any of the six methods tested, was similar and provides a reliable model of axonotmesis.

Neurosteroids in cerebrospinal fluid in neurologic disorders

In order to investigate the role of “neurosteroids” in the central nervous system (CNS), cerebrospinal fluid (CSF) levels of dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) were determined by radioimmunoassay in 57 patients with various neurologic disorders and 26 patients with non-neurologic disorders. The content of CSF DHEA and DHEAS in patients with Guillain-Barré syndrome (GBS), and the content of CSF DHEAS in patients with carcinomatous meningitis were significantly higher as compared to non-neurological control patients. These changes may be explained by the breakdown of blood-nerve barrier in these disorders. A significant positive correlation was observed between DHEAS and total protein in CSF. In males but not females, a negative correlation was observed between CSF DHEAS and aging. The level of CSF DHEAS, but not DHEA, was significantly higher in males than in females.

Gd-DTPA enhanced MR of the lumbar spinal canal in patients with claudication.

The purpose of this work was to study the findings on intravenous gadolinium-enhanced MRI of the lumbar spinal canal in patients with clinically suspected neurogenic claudication. A prospective gadolinium-enhanced MR evaluation of seven adult patients presenting with clinical claudication thought to be related to the lumbosacral spine was undertaken. Of seven consecutive enhanced conventional SE MRI examinations of the lumbosacral spine in patients presenting with lower extremity claudication, five patients (71.4%) revealed abnormal intrathecal enhancement on MR at and extending craniad from the level(s) of severe spinal stenosis. Each of the seven patients (100%) showed relatively severe central stenosis of the lumbar spinal canal. The enhancement pattern was linear, curvilinear, punctate, and/or diffuse in configuration. Two of the five patients with intrathecal enhancement also showed similar abnormal intrathecal enhancement extending caudal to the severely stenotic levels. The clinically significant intrathecal enhancement on intravenous gadolinium-enhanced MRI identified above the level of a severely stenotic lumbar spinal canal hypothetically might represent enhancement of dilated, obstructed venous structures serving the cauda equina. More likely, however, the major factor in such enhancement at, above, and/or below the stenosis signals blood-nerve barrier breakdown associated with mechanical injury, inflammatory response, and wallerian degeneration/regeneration of axons within chronically compressed nerve roots.

Restoration of Blood-Nerve Barrier in Neuropathy is Associated with Axonal Regeneration and Remyelination

We investigated the temporal course of blood-nerve barrier (BNB) breakdown during the evolution of tellurium neuropathy, ricin neuropathy, and Wallerian degeneration following nerve transection or nerve crush. Blood-nerve barrier permeability was assessed with a 4,000-molecular weight fluoresceinated dextran from three days to 19 weeks after onset of neuropathy. Blood-nerve barrier breakdown was present during the first two weeks in all four models of neuropathy. Restoration of the BNB to the dextran began within four weeks and was complete by 14 weeks in tellurium neuropathy, a model of demyelinating neuropathy characterized by rapid remyelination, and after nerve crush, a model of Wallerian degeneration characterized by rapid axonal regeneration into distal stump. In contrast, there was persistence of BNB breakdown beyond 14 weeks in ricin neuropathy, a model of neuropathy with no axonal regeneration or remyelination, and after nerve transection, a model of Wallerian degeneration characterized by minimal axonal regeneration into distal stump. We conclude from these data that alterations in the BNB over the course of neuropathy differ among various types of neuropathy, and that these alterations are dependent on the form of nerve fiber injury. The lack of regenerating or remyelinating axons in ricin neuropathy and after nerve transection may be responsible for the persistent BNB breakdown found in these neuropathies.