Roscoe Atkinson

Neural anatomy of the glenohumeral ligaments, labrum, and subacromial bursa☆

The neural histology of the human shoulder ligaments, glenoid labrum, and subacromial bursae were studied using a modified gold chloride stain. Two morphological types of mechanoreceptors and free nerve endings were found in the ligaments. Slow adapting Ruffini end organs and rapidly adapting Pacinian corpuscles were identified in the superior, middle, inferior, and the posterior glenohumeral ligaments. These specialized proprioceptive nerve endings were also found in the coracoclavicular, and coracoacromial ligaments. Only free nerve endings were found in the glenoid labrum and these were located in the peripheral half. Scattered free nerve endings were found throughout the subacromial bursae. This is the first histological evidence of neural receptors in the human shoulder ligaments, glenoid labrum, and the subacromial bursae. Any disruption of the labrum or these ligaments by trauma or surgery can deprive the shoulder of mechanical stability, and may cause a decrease in proprioception because of the loss of these afferent neural receptors. Removal of symptomatic, inflamed bursae may decrease pain signals from this area of the shoulder.

Matrix metalloproteinases in the neocortex and spinal cord of amyotrophic lateral sclerosis patients.

Abstract: Matrix metalloproteinases (MMPs) were analyzed by immunohistochemistry and zymography in amyotrophic lateral sclerosis (ALS) and control brain and spinal cord specimens. Three major bands of enzyme activity (70, 100, and 130 kDa) were consistently observed and were subsequently identified as MMP‐2 (70 kDa; also known as EC 3.4.24.24 or gelatinase A) and MMP‐9 (100 and 130 kDa; also known as EC 3.4.24.35 or gelatinase B). Immunohistochemical studies established the presence of MMP‐2 in astrocytes and MMP‐9 in pyramidal neurons in the motor cortex and motor neurons in the spinal cord of ALS patients. Although a significant decrease in MMP‐2 activity was noticed in the ALS motor cortex, statistically significant increases in MMP‐9 (100‐kDa) activity were observed in ALS frontal and occipital cortices (BA10 and 17) and all three spinal cord regions when compared with control specimens. The highest MMP‐9 (100‐kDa) activities in ALS were found in the motor cortex and thoracic and lumbar cord specimens. The abnormally high amount of MMP‐9 and its possible release at the synapse may destroy the structural integrity of the surrounding matrix, thereby contributing to the pathogenesis of ALS.

Role of Differentiation of Liver Sinusoidal Endothelial Cells in Progression and Regression of Hepatic Fibrosis in Rats

BACKGROUND & AIMS Capillarization, characterized by loss of differentiation of liver sinusoidal endothelial cells (LSECs), precedes the onset of hepatic fibrosis. We investigated whether restoration of LSEC differentiation would normalize crosstalk with activated hepatic stellate cells (HSC) and thereby promote quiescence of HSC and regression of fibrosis. METHODS Rat LSECs were cultured with inhibitors and/or agonists and examined by scanning electron microscopy for fenestrae in sieve plates. Cirrhosis was induced in rats using thioacetamide, followed by administration of BAY 60-2770, an activator of soluble guanylate cyclase (sGC). Fibrosis was assessed by Sirius red staining; expression of α-smooth muscle actin was measured by immunoblot analysis. RESULTS Maintenance of LSEC differentiation requires vascular endothelial growth factor-A stimulation of nitric oxide-dependent signaling (via sGC and cyclic guanosine monophosphate) and nitric oxide-independent signaling. In rats with thioacetamide-induced cirrhosis, BAY 60-2770 accelerated the complete reversal of capillarization (restored differentiation of LSECs) without directly affecting activation of HSCs or fibrosis. Restoration of differentiation to LSECs led to quiescence of HSCs and regression of fibrosis in the absence of further exposure to BAY 60-2770. Activation of sGC with BAY 60-2770 prevented progression of cirrhosis, despite continued administration of thioacetamide. CONCLUSIONS The state of LSEC differentiation plays a pivotal role in HSC activation and the fibrotic process.

Mechanisms of central nervous system viral persistence: the critical role of antibody and B cells.

Contributions of humoral and cellular immunity in controlling neurotropic mouse hepatitis virus persistence within the CNS were determined in B cell-deficient JHD and syngeneic H-2d B cell+ Ab-deficient mice. Virus clearance followed similar kinetics in all mice, confirming initial control of virus replication by cellular immunity. Nevertheless, virus reemerged within the CNS of all Ab-deficient mice. In contrast to diminished T cell responses in H-2b B cell-deficient μMT mice, the absence of B cells or Ab in the H-2d mice did not compromise expansion, recruitment into the CNS, or function of virus-specific CD4+ and CD8+ T cells. The lack of B cells and lymphoid architecture thus appears to manifest itself on T cell responses in a genetically biased manner. Increasing viral load did not enhance frequencies or effector function of virus-specific T cells within the CNS, indicating down-regulation of T cell responses. Although an Ab-independent antiviral function of B cells was not evident during acute infection, the presence of B cells altered CNS cellular tropism during viral recrudescence. Reemerging virus localized almost exclusively to oligodendroglia in B cell+ Ab-deficient mice, whereas it also replicated in astrocytes in B cell-deficient mice. Altered tropism coincided with distinct regulation of CNS virus-specific CD4+ T cells. These data conclusively demonstrate that the Ab component of humoral immunity is critical in preventing virus reactivation within CNS glial cells. B cells themselves may also play a subtle role in modulating pathogenesis by influencing tropism.

Type I Interferons Are Essential in Controlling Neurotropic Coronavirus Infection Irrespective of Functional CD8 T Cells

ABSTRACT Neurotropic coronavirus infection induces expression of both beta interferon (IFN-β) RNA and protein in the infected rodent central nervous system (CNS). However, the relative contributions of type I IFN (IFN-I) to direct, cell-type-specific virus control or CD8 T-cell-mediated effectors in the CNS are unclear. IFN-I receptor-deficient (IFNAR−/−) mice infected with a sublethal and demyelinating neurotropic virus variant and those infected with a nonpathogenic neurotropic virus variant both succumbed to infection within 9 days. Compared to wild-type (wt) mice, replication was prominently increased in all glial cell types and spread to neurons, demonstrating expanded cell tropism. Furthermore, increased pathogenesis was associated with significantly enhanced accumulation of neutrophils, tumor necrosis factor alpha, interleukin-6, chemokine (C-C motif) ligand 2, and IFN-γ within the CNS. The absence of IFN-I signaling did not impair induction or recruitment of virus-specific CD8 T cells, the primary adaptive mediators of virus clearance in wt mice. Despite similar IFN-γ-mediated major histocompatibility complex class II upregulation on microglia in infected IFNAR−/− mice, class I expression was reduced compared to that on microglia in wt mice, suggesting a synergistic role of IFN-I and IFN-γ in optimizing class I antigen presentation. These data demonstrate a critical direct antiviral role of IFN-I in controlling virus dissemination within the CNS, even in the presence of potent cellular immune responses. By limiting early viral replication and tropism, IFN-I controls the balance of viral replication and immune control in favor of CD8 T-cell-mediated protective functions.

Liver X receptor activation decreases the severity of experimental autoimmune encephalomyelitis

Agonists of liver X receptors (LXR), members of the nuclear hormone receptor superfamily, alter secretion of proinflammatory cytokines, suggesting potential antiinflammatory effects. A synthetic LXR agonist inhibited T‐cell proliferation and cytokine release in a dose‐dependent manner. Treatment of mice during induction of experimental autoimmune encephalomyelitis reduced clinical symptoms, central nervous system cellular inflammation, and major histocompatibility class II expression on microglia, as well as demyelination. In contrast to in vitro analysis, no reductions in peripheral neuroantigen specific T‐cell responses were detected in comparing ligand and vehicle treated mice. These data suggest that LXR agonists play an important protective role in the regulation of T‐cell‐mediated inflammatory disease of the central nervous system.

Prevention of Hepatic Fibrosis in a Murine Model of Metabolic Syndrome with Nonalcoholic Steatohepatitis

The endocannabinoid pathway plays an important role in the regulation of appetite and body weight, hepatic lipid metabolism, and fibrosis. Blockade of the endocannabinoid receptor CB1 with SR141716 promotes weight loss, reduces hepatocyte fatty acid synthesis, and is antifibrotic. D-4F, an apolipoprotein A-1 mimetic with antioxidant properties, is currently in clinical trials for the treatment of atherosclerosis. C57BL/6J mice were fed a high-fat diet for 7 months, followed by a 2.5-month treatment with either SR141716 or D-4F. SR141716 markedly improved body weight, liver weight, serum transaminases, insulin resistance, hyperglycemia, hypercholesterolemia, hyperleptinemia, and oxidative stress, accompanied by the significant prevention of fibrosis progression. D-4F improved hypercholesterolemia and hyperleptinemia without improvement in body weight, steatohepatitis, insulin resistance, or oxidative stress, and yet, there was significant prevention of fibrosis. D-4F prevented culture-induced activation of stellate cells in vitro. In summary, C57BL/6J mice given a high-fat diet developed features of metabolic syndrome with nonalcoholic steatohepatitis and fibrosis. Both SR141716 and D-4F prevented progression of fibrosis after onset of steatohepatitis, ie, a situation comparable to a common clinical scenario, with D-4F seeming to have a more general antifibrotic effect. Either compound therefore has the potential to be of clinical benefit.

CNS viral infection diverts homing of antibody-secreting cells from lymphoid organs to the CNS

Neurotropic coronavirus infection of mice results in acute encephalomyelitis followed by viral persistence. Whereas cellular immunity controls acute infection, humoral immunity regulates central nervous system (CNS) persistence. Maintenance of serum Ab was correlated with tissue distribution of virus‐specific Ab‐secreting cells (ASC). Although virus‐specific ASC declined in cervical lymph node and spleen after infectious virus clearance, virus‐specific serum Ab was sustained at steady levels, with a delay in neutralizing Ab. Virus‐specific ASC within the CNS peaked rapidly 1 wk after control of infectious virus and were retained throughout chronic infection, consistent with intrathecal Ab synthesis. Surprisingly, frequencies of ASC in the BM remained low and only increased gradually. Nevertheless, virus‐specific ASC induced by peripheral infection localized to both spleen and BM. The data suggest that CNS infection provides strong stimuli to recruit ASC into the inflamed tissue through sustained up‐regulation of the CXCR3 ligands CXCL9 and CXCL10. Irrespective of Ag deprivation, CNS retention of ASC coincided with elevated BAFF expression and ongoing differentiation of class II+ to class II–CD138+CD19+ plasmablasts. These results confirm the CNS as a major ASC‐supporting environment, even after resolution of viral infection and in the absence of chronic ongoing inflammation.

Monocytes Regulate T Cell Migration through the Glia Limitans during Acute Viral Encephalitis

ABSTRACT Leukocyte access into the central nervous system (CNS) parenchyma is tightly regulated by the blood-brain barrier (BBB). Leukocyte migration through the endothelial cell wall into the perivascular space is well characterized; however, mechanisms regulating their penetration through the glia limitans into the parenchyma are less well studied, and the role of monocytes relative to neutrophils is poorly defined. Acute viral encephalitis was thus induced in CCL2-deficient (CCL2−/−) mice to specifically abrogate monocyte recruitment. Impaired monocyte recruitment prolonged T cell retention in the perivascular space, although no difference in overall CNS accumulation of CD4 or CD8 T cells was detected by flow cytometry. Delayed penetration to the CNS parenchyma was not associated with reduced or altered expression of either matrix metalloproteinases (MMP) or the T cell chemoattractants CXCL10 and CCL5. Nevertheless, decreased parenchymal leukocyte infiltration delayed T cell-mediated control of virus replication as well as clinical disease. These data are the first to demonstrate that the rapid monocyte recruitment into the CNS during viral encephalitis is dispensable for T cell migration across the blood vessel endothelium. However, monocytes facilitate penetration through the glia limitans. Thus, the rapid monocyte response to viral encephalitis constitutes an indirect antiviral pathway by aiding access of effector T cells to the site of viral infection.

Contributions of Fas-Fas Ligand Interactions to the Pathogenesis of Mouse Hepatitis Virus in the Central Nervous System

ABSTRACT The pathogenesis of the neurotropic strain of mouse hepatitis virus in Fas-deficient mice suggested that Fas-mediated cytotoxicity may be required during viral clearance after the loss of perforin-mediated cytotoxicity. The absence of both Fas- and perforin-mediated cytolysis resulted in an uncontrolled infection, suggesting a redundancy of cytolytic pathways to control virus replication.