In a basic science laboratory study of HIV-exposed neurons, fingolimod upregulated the expression of a number of genes, including NESTIN, a structural protein found in progenitor cells; MAP2, a protein involved in microtubule processes; SOX2, a transcription factor found in immature cells; and S1Pr1, S1Pr3 and S1Pr5, three forms of the sphingosine-1-phosphate receptor that fingolimod binds to; as well as native immune response genes such as IFI6, which is thought to play a role in the regulation of apoptosis, lead investigator Micheline McCarthy, MD, of the University of Miami Miller School of Medicine and the Miami VA HealthCare System, told MedPage Today. The work was presented here at the American Neurological Association‘s annual meeting.

Fingolimod is a sphingosine-1-phosphate receptor modulator that prevents MS relapses by sequestering lymphocytes in lymph nodes, it is believed, preventing them from circulating and contributing to an autoimmune reaction. But the current study suggests it may have an independent neuroprotective effect.

“If validated, the data indicate that fingolimod may have a protective role on human neuronal progenitors and maturing neurons by promoting neurogenesis and preventing apoptosis,” McCarthy said. The results were interesting, she added: “People don’t think of neurons as immunologically active cells but they do actually have some capacity to mount an immune response.”

During phase III clinical trials of fingolimod, the first oral disease-modifying drug approved by the FDA for the relapsing form of MS, there were indications that brain volume loss was slower in patients taking the drug, McCarthy said: “That’s raised the question of whether fingolimod has the ability to protect neurons.”

HIV, one of McCarthy’s areas of interests, “is well known for its devastating effects on the brain, and even though neurons are not known to be to be infected directly by HIV, exposure to HIV or HIV proteins causes neuronal toxicity and neuronal cell death,” she said. “Even in well-controlled infection in which antivirals suppress the virus replication in circulation, there is still a long-term impact of the chronic infection and inflammation that goes with it on cognition.”

For the study, McCarthy and colleagues adapted human neuronal progenitor cell line hNP1, derived from human embryonic stem cell line WA09, to test the neuroprotective capacity of fingolimod in neurons exposed to HIV.

HNP1 cells were differentiated in medium alone, or in medium with added supernatants from mock-infected or HIV-infected lymphocytes, with or without added fingolimod. Fingolimod’s effect on the cells initially was studied in concentrations of 10 μM, 1μM, 100 nM, and 10 nM. Higher concentrations of the drug proved to be toxic to the cells.

In other experiments, duplicate cultures of hNP1 cells were incubated with differentiation medium alone (untreated) or with differentiation medium containing 100 nM unphosphorylated fingolimod. On days 11, 12, 18, and 20, McCarthy and colleagues harvested cells and used reverse transcriptase polymerase chain reaction (RT-PCR) to look for expression of genes for neurogenesis, neuronal function, and immune response.

The team also studied the drug’s impact on cells incubated alone or with mock supernatants from uninfected peripheral blood mononuclear cell (PBMC) cultures stimulated with phytohaemagglutinin and interleukin-2, performing RT-PCR on the cells on days 12, 18, and 20. And they studied fingolimod’s effect on hNP1 cells incubated with differentiation medium containing 10 mg p24 equivalent per ml of HIV, or mock supernatants from uninfected, mitogen activated PBMC cultures, conducting RT-PCR on days 12, 18, and 20.

Gene expression in cells exposed to mock supernatants was not affected by fingolimod. “Thus, fingolimod may enhance the expression of certain neuronal genes in HIV-exposed human neurons, possibly protecting against negative viral effects on gene expression,” McCarthy and colleagues wrote in their abstract.

“The implication is that the drug could be used to protect neurons from the degenerative phase of (MS),” McCarthy said. “The other possibility is it might have some role in HIV infection in chronic, well-controlled HIV infection to prevent neurologic decline.” She and her colleagues are planning a larger microarray study of genes affected by HIV and fingolimod.