New Horizons in Chemical Functionalization of Endohedral Metallofullerenes.

This overview explains some new aspects of chemical functionalization of endohedral metallofullerenes (EMFs) that have been unveiled in recent years. After differences in chemical reactivity between EMFs and the corresponding empty fullerenes are discussed, cage-opening reactions of EMFs are examined. Then, the selective bisfunctionalization of EMFs is explained. Finally, single-bonding derivatization of EMFs is addressed. The diversity and applicability of the chemical functionalization of endohedral metallofullerenes are presented to readers worldwide.

Regioselective bis-functionalization of endohedral dimetallofullerene, La2@C80: extremal La-La distance.

Bis-functionalization of endohedral metallofullerene La(2)@C(80) by carbene addition is reported herein. Adducts were characterized using spectroscopic and single-crystal X-ray structure analyses. Crystallographic data for bisadduct La(2)@C(80)(CClPh)Ad (3, Ad = adamantylidene) revealed that both carbene additions occur at the 6,6-bond junction on the C(80) cage with ring cleavages and that La atoms are positioned collinearly with spiro carbons. It is noteworthy that the La-La distance in 3 is highly elongated by carbene bis-functionalization compared to the distance in pristine La(2)@C(80) and reported functionalized derivatives. The metal positions were confirmed through density functional calculations.

CXCL10 and trafficking of virus-specific T cells during coronavirus-induced demyelination.

Chronic expression of CXC chemokine ligand 10 (CXCL10) in the central nervous system (CNS) following infection with the neurotropic JHM strain of mouse hepatitis virus (JHMV) is associated with an immune-mediated demyelinating disease. Treatment of mice with anti-CXCL10 neutralizing antibody results in limited CD4+ T cell infiltration into the CNS accompanied by a reduction in white matter damage. The current study determines the antigen-specificity of the T lymphocytes present during chronic disease and evaluates how blocking CXCL10 signaling affects retention of virus-specific T cells within the CNS. CXCL10 neutralization selectively reduced accumulation and/or retention of virus-specific CD4+ T cells, yet exhibited limited effect on virus-specific CD8+ T cells. The response of CXCL10 neutralization on virus-specific T cell subsets is not due to differential expression of the CXCL10 receptor CXCR3 on T cells as there was no appreciable difference in receptor expression on virus-specific T cells during either acute or chronic disease. These findings emphasize the importance of virus-specific CD4+ T cells in amplifying demyelination in JHMV-infected mice. In addition, differential signals are required for trafficking and retention of virus-specific CD4+ and CD8+ T cells during chronic demyelination in JHMV-infected mice.

Does Gd@C82 have an anomalous endohedral structure? Synthesis and single crystal X-ray structure of the carbene adduct.

We report here the results on single crystal X-ray crystallographic analysis of the Gd@C82 carbene adduct (Gd@C82(Ad), Ad = adamantylidene). The Gd atom in Gd@C82(Ad) is located at an off-centered position near a hexagonal ring in the C2v-C82 cage, as found for M@C82 (M = Sc and La) and La@C82(Ad). Theoretical calculation also confirms the position of the Gd atom in the X-ray crystal structure.

Isolation and characterization of carbene derivatives of La@C82(Cs).

The photochemical reaction of La@C82(Cs) with 2-adamantane-2,3-[3H]-diazirine (1) affords the adduct 2 of La@C82(Cs) with adamantylidene (Ad:) in a high selectivity. The two isomers of La@C82(Cs)(Ad), 2a and 2b, are isolated by HPLC and characterized by electron spin resonance, mass, and UV-vis-near-infrared spectroscopies. The electronic properties of 2a and 2b are very similar to that of the pristine La@C82(Cs), suggesting that 2a and 2b retain the essential electronic and structural character of La@C82(Cs).

Metal atoms collinear with the spiro carbon of 6,6-open adducts, M2@C80(Ad) (M = La and Ce, Ad = adamantylidene).

The photochemical reaction of M2@C80 (M = La and Ce) with 2-adamantane-2,3'-[3H]-diazirine (1) affords the corresponding adducts by carbene addition. The adducts were characterized by spectroscopic and single-crystal X-ray structure analyses. Crystallographic data for the adduct La2@C80(Ad) (2, Ad = adamantylidene) reveal that the two La atoms are collinear with the spiro carbon of the 6,6-open adduct. It is noteworthy that the La-La distance is highly elongated by the addition of carbene. Paramagnetic 13C NMR spectral analysis of the adduct Ce2@C80(Ad) (3) indicates that the two Ce atoms are also collinear with the spiro carbon at room temperature in solution. The unique metal positions were confirmed by density functional calculations.

Structural determination of metallofullerene Sc3C82 revisited: a surprising finding.

We report here the structural determination of the Sc3C82 molecule by 13C NMR spectroscopy and X-ray single-crystal structure analysis. From the present study, it is obvious that the structure of Sc3C82 is not Sc3@C82 but Sc3C2@C80.

Neutralization of chemokines RANTES and MIG increases virus antigen expression and spinal cord pathology during Theiler's virus infection.

The role of chemokines during some viral infections is unpredictable because the inflammatory response regulated by these molecules can have two, contrasting effects-viral immunity and immunopathologic injury to host tissues. Using Theiler's virus infection of SJL mice as a model of this type of disease, we have investigated the roles of two chemokines-regulated on activation, normal T cell-expressed and secreted (RANTES) chemokine and monokine induced by IFN-gamma (MIG)-by treating mice with antisera that block lymphocyte migration. Control, infected mice showed virus persistence, mild inflammation and a small degree of demyelination in the white matter of the spinal cord at 6 weeks post-infection. Treatment of mice with RANTES antiserum starting at 2 weeks post-infection increased both viral antigen expression and the severity of inflammatory demyelination at 6 weeks post-infection. MIG antiserum increased the spread of virus and the proportion of spinal cord white matter with demyelination. Overall, viral antigen levels correlated strongly with the extent of pathology. At the RNA level, high virus expression was associated with low IL-2 and high IL-10 levels, and RANTES antiserum decreased the IL-2/IL-10 ratio. Our results suggest that RANTES and MIG participate in an immune response that attempts to restrict viral expression while limiting immunopathology and that anti-chemokine treatment poses the risk of exacerbating both conditions in the long term.

Isolation and characterization of a carbene derivative of La@C82.

The photochemical reaction of La@C82 with 2-adamantane-2,3-[3H]-diazirine affords adduct 2, La@C82(Ad), in a quantitative and highly selective manner. The structure of compound 2 is confirmed by ESR, MS, and UV-vis-NIR spectroscopies, and the first X-ray crystallographic characterization of an endohedral monometallofullerene derivative is reported.

Antibody targeting of the CC chemokine ligand 5 results in diminished leukocyte infiltration into the central nervous system and reduced neurologic disease in a viral model of multiple sclerosis.

Intracerebral infection of mice with mouse hepatitis virus, a member of the Coronaviridae family, reproducibly results in an acute encephalomyelitis that progresses to a chronic demyelinating disease. The ensuing neuropathology during the chronic stage of disease is primarily immune mediated and similar to that of the human demyelinating disease multiple sclerosis. Secretion of chemokines within the CNS signals the infiltration of leukocytes, which results in destruction of white matter and neurological impairment. The CC chemokine ligand (CCL)5 is localized in white matter tracts undergoing demyelination, suggesting that this chemokine participates in the pathogenesis of disease by attracting inflammatory cells into the CNS. In this study, we administer a mAb directed against CCL5 to mice with established mouse hepatitis virus-induced demyelination and impaired motor skills. Anti-CCL5 treatment decreased T cell accumulation within the CNS based, in part, on viral Ag specificity, indicating the ability to differentially target select populations of T cells. In addition, administration of anti-CCL5 improved neurological function and significantly (p < or = 0.005) reduced the severity of demyelination and macrophage accumulation within the CNS. These results demonstrate that the severity of CNS disease can be reduced through the use of a neutralizing mAb directed against CCL5 in a viral model of demyelination.

Reducing inflammation decreases secondary degeneration and functional deficit after spinal cord injury.

Injury to the spinal cord is followed by degeneration, which leads to progressive tissue loss and usually cystic cavitation. Cellular and humoral immune responses have been implicated as mediators of secondary degeneration, and the expression of leukocyte chemoattractants has been shown to precede immune cell influx. However, the relationship between the increased expression of chemoattractants, the invasion of lymphocytes, and overall lesion evolution is poorly understood. Here, we show that the T-lymphocyte chemoattractant CXCL10 is upregulated after dorsal hemisection injury to the adult mammalian spinal cord of C57/BL6 mice, and that antibody neutralization of CXCL10 beginning 1 day prior to injury dramatically reduces the T-lymphocyte invasion that normally occurs after trauma. Notably, this treatment resulted in a significant reduction of secondary tissue loss and functional deficit. We conclude that CXCL10 plays a critical role in recruitment of T lymphocytes to sites of spinal cord injury, and that a reduction of T-lymphocyte recruitment significantly enhances tissue preservation and functional outcome.

Effect of substituents on the thermal decomposition of diazirines: experimental and computational studies.

The thermal decomposition of phenylchlorodiazirine (1), phenyl-n-butyldiazirine (2), and 2-adamantane-2,3'-[3H]diazirine (3) has been studied in solution in the presence of C(60). The C(60) probe technique indicates that in the decomposition diazirine 1 yielded exclusively phenylchlorocarbene, diazirine 2 yielded mainly a diazo intermediate, and diazirine 3 yielded a mixture of carbene and diazo compound. In the case of diazirine 2, 13% of (E)-1-phenyl-1-pentene resulted from the direct thermal rearrangement of diazirine without the participation of a carbene. As well, the thermal decomposition of these diazirines has been studied theoretically with ab initio and density functional methods. The experimental results are broadly in agreement with the theoretical predictions. The calculations further indicate that the rebound reaction between carbene and molecular nitrogen leading to the formation of a diazo intermediate is an important reaction in the gas-phase decomposition of diazirine.

A nonspectroscopic method to determine the photolytic decomposition pathways of 3-chloro-3-alkyldiazirine: carbene, diazo and rearrangement in excited state.

C(60) acts as a mechanistic probe for the formation of carbene, diazo compound, and for the rearranged product via the excited state in the photolysis of 3-chloro-3-isopropyldiazirine and 3-chloro-3-chloromethyldiazirine. The carbene adds to C(60) to form methanofullerene, whereas the diazo compound adds to C(60) to form fulleroid. The olefin product arises as a result of the rearrangement in the excited state.

Mouse hepatitis virus infection of the central nervous system: chemokine-mediated regulation of host defense and disease.

Infection of the central nervous system (CNS) of susceptible mice with mouse hepatitis virus (MHV), a positive-strand RNA virus that is a member of the Coronaviridae family, reproducibly results in an acute encephalomyelitis followed by a demyelinating disease similar to the human demyelinating disease multiple sclerosis (MS). MHV infection triggers a robust cell-mediated response in which both CD4+ and CD8+ T cells are essential in controlling viral replication and spread. However, viral clearance is incomplete and viral RNA and protein can persist within white matter tracts, areas of viral persistence are often associated with demyelinating lesions, and recent studies have indicated an important role for both T cells and macrophages in contributing to myelin destruction. The molecular mechanisms governing leukocyte trafficking and accumulation within the CNS of MHV-infected mice are just now being understood and recent studies indicate that chemokines and chemokine receptors have an important role in this process. This article will provide an overview on how these molecules regulate T cell and macrophage trafficking into the CNS of MHV-infected mice and illustrate the delicate balance that exists with regards to expression of chemokines and their receptors as it relates to both host defense and disease development.

IFN-gamma-inducible protein 10 (IP-10; CXCL10)-deficient mice reveal a role for IP-10 in effector T cell generation and trafficking.

IFN-gamma-inducible protein 10 (IP-10, CXCL10), a chemokine secreted from cells stimulated with type I and II IFNs and LPS, is a chemoattractant for activated T cells. Expression of IP-10 is seen in many Th1-type inflammatory diseases, where it is thought to play an important role in recruiting activated T cells into sites of tissue inflammation. To determine the in vivo function of IP-10, we constructed an IP-10-deficient mouse (IP-10(-/-)) by targeted gene disruption. Immunological analysis revealed that IP-10(-/-) mice had impaired T cell responses. T cell proliferation to allogeneic and antigenic stimulation and IFN-gamma secretion in response to antigenic challenge were impaired in IP-10(-/-) mice. In addition, IP-10(-/-) mice exhibited an impaired contact hypersensitivity response, characterized by decreased ear swelling and reduced inflammatory cell infiltrates. T cells recovered from draining lymph nodes also had a decreased proliferative response to Ag restimulation. Furthermore, IP-10(-/-) mice infected with a neurotropic mouse hepatitis virus had an impaired ability to control viral replication in the brain. This was associated with decreased recruitment of CD4(+) and CD8(+) lymphocytes into the brain, reduced levels of IFN-gamma and the IFN-gamma-induced chemokines monokine induced by IFN-gamma (Mig, CXCL9) and IFN-inducible T cell alpha chemoattractant (I-TAC, CXCL11) in the brain, decreased numbers of virus-specific IFN-gamma-secreting CD8(+) cells in the spleen, and reduced levels of demyelination in the CNS. Taken together, our data suggest a role for IP-10 in both effector T cell generation and trafficking in vivo.