Formulation and Profile of FMX101 4% Minocycline Topical Foam for the Treatment of Acne Vulgaris.

FMX101 4% minocycline is a hydrophobic, topical foam formulation of minocycline recently approved by the United States Food and Drug Administration (FDA) for the treatment of non-nodular inflammatory lesions in moderate-to-severe acne vulgaris. It was developed to harness the anti-inflammatory and antibiotic activity of minocycline while minimizing potentially serious systemic adverse events associated with oral delivery. The composition and profile of this novel treatment have yet to be described. This article discusses the components of the foam-based product and the rationale for their selection. It reviews microbiologic data for FMX101 4% and presents previously unpublished data regarding sebum penetration, minocycline permeation, and disposition into skin structures. The effects of FMX101 4% were compared with those of several commercially available acne preparations to determine how the FMX101 4% formulation affects the physical properties of model human sebum in vitro. The hydrophobic formulation of FMX101 4% was found to lower the melting temperature of model human sebum below that of normal skin temperature, decreasing its viscosity. FMX101 4% achieved high concentrations of minocycline in the sebaceous appendage, while minimizing permeation beyond the dermal layer. Finally, this article summarizes efficacy and safety data for FMX101 4% from three Phase III studies (FX2014-04, FX2014-05, and FX2017-22). FMX101 4% appeared to be safe, effective, and well tolerated for the treatment of non-nodular inflammatory lesions in moderate-to-severe acne vulgaris. In conclusion, the topical formulation of minocycline in FMX101 4% represents a unique treatment for acne vulgaris and a viable alternative to oral administration.

CNS repair requires both effector and regulatory T cells with distinct temporal and spatial profiles.

Monocyte-derived macrophages (mo-MΦs) and T cells have been shown to contribute to spinal cord repair. Recently, the remote brain choroid plexus epithelium (CP) was identified as a portal for monocyte recruitment, and its activation for leukocyte trafficking was found to be IFN-γ-dependent. Here, we addressed how the need for effector T cells can be reconciled with the role of inflammation-resolving immune cells in the repair process. Using an acute spinal cord injury model, we show that in mice deficient in IFN-γ-producing T cells, the CP was not activated, and recruitment of inflammation-resolving mo-MΦ to the spinal cord parenchyma was limited. We further demonstrate that mo-MΦ locally regulated recruitment of thymic-derived Foxp3(+) regulatory T (Treg) cells to the injured spinal cord parenchyma at the subacute/chronic phase. Importantly, an ablation protocol that resulted in reduced Tregs at this stage interfered with tissue remodeling, in contrast to Treg transient ablation, restricted to the 4 d period before the injury, which favored repair. The enhanced functional recovery observed following such a controlled decrease of Tregs suggests that reduced systemic immunosuppression at the time of the insult can enhance CNS repair. Overall, our data highlight a dynamic immune cell network needed for repair, acting in discrete compartments and stages, and involving effector and regulatory T cells, interconnected by mo-MΦ. Any of these populations may be detrimental to the repair process if their level or activity become dysregulated. Accordingly, therapeutic interventions must be both temporally and spatially controlled.

Microglia and monocyte-derived macrophages: functionally distinct populations that act in concert in CNS plasticity and repair.

Functional macrophage heterogeneity is recognized outside the central nervous system (CNS), where alternatively activated macrophages can perform immune-resolving functions. Such functional heterogeneity was largely ignored in the CNS, with respect to the resident microglia and the myeloid-derived cells recruited from the blood following injury or disease, previously defined as blood-derived microglia; both were indistinguishably perceived detrimental. Our studies have led us to view the myeloid-derived infiltrating cells as functionally distinct from the resident microglia, and accordingly, to name them monocyte-derived macrophages (mo-MΦ). Although microglia perform various maintenance and protective roles, under certain conditions when they can no longer provide protection, mo-MΦ are recruited to the damaged CNS; there, they act not as microglial replacements but rather assistant cells, providing activities that cannot be timely performed by the resident cells. Here, we focus on the functional heterogeneity of microglia/mo-MΦ, emphasizing that, as opposed to the mo-MΦ, microglia often fail to timely acquire the phenotype essential for CNS repair.

Recruitment of beneficial M2 macrophages to injured spinal cord is orchestrated by remote brain choroid plexus.

Monocyte-derived macrophages are essential for recovery after spinal cord injury, but their homing mechanism is poorly understood. Here, we show that although of common origin, the homing of proinflammatory (M1) and the "alternatively activated" anti-inflammatory (M2) macrophages to traumatized spinal cord (SC) was distinctly regulated, neither being through breached blood-brain barrier. The M1 macrophages (Ly6c(hi)CX3CR1(lo)) derived from monocytes homed in a CCL2 chemokine-dependent manner through the adjacent SC leptomeninges. The resolving M2 macrophages (Ly6c(lo)CX3CR1(hi)) derived from monocytes trafficked through a remote blood-cerebrospinal-fluid (CSF) barrier, the brain-ventricular choroid plexus (CP), via VCAM-1-VLA-4 adhesion molecules and epithelial CD73 enzyme for extravasation and epithelial transmigration. Blockage of these determinants, or mechanical CSF flow obstruction, inhibited M2 macrophage recruitment and impaired motor-function recovery. The CP, along with the CSF and the central canal, provided an anti-inflammatory supporting milieu, potentially priming the trafficking monocytes. Overall, our finding demonstrates that the route of monocyte entry to central nervous system provides an instructional environment to shape their function.

Functional macrophage heterogeneity in a mouse model of autoimmune central nervous system pathology.

Functional macrophage heterogeneity is well appreciated outside the CNS in wound healing and cancer, and was recently also demonstrated in several CNS compartments after "sterile" insults. Yet, such heterogeneity was largely overlooked in the context of inflammatory autoimmune pathology, in which macrophages were mainly associated with disease induction and propagation. In this article, we show the diversity of monocyte-derived macrophages along the course of experimental autoimmune uveitis, an inflammatory condition affecting the ocular system, serving as a model for CNS autoimmune pathology. Disease induction resulted in the appearance of a distinct myeloid population in the retina, and in the infiltration of monocyte-derived macrophages that were absent from control eyes. During the disease course, the frequency of CX3CR1(high) infiltrating macrophages that express markers associated with inflammation-resolving activity was increased, along with a decrease in the frequency of inflammation-associated Ly6C(+) macrophages. Inhibition of monocyte infiltration at the induction phase of experimental autoimmune uveitis prevented disease onset, whereas monocyte depletion at the resolution phase resulted in a decrease in Foxp3(+) regulatory T cells and in exacerbated disease. Thus, monocyte-derived macrophages display distinct phenotypes throughout the disease course, even in an immune-induced pathology, reflecting their differential roles in disease induction and resolution.

Orchestrated leukocyte recruitment to immune-privileged sites: absolute barriers versus educational gates.

Complex barriers separate immune-privileged tissues from the circulation. Here, we propose that cell entry to immune-privileged sites through barriers composed of tight junction-interconnected endothelium is associated with destructive inflammation, whereas border structures comprised of fenestrated vasculature enveloped by tightly regulated epithelium serve as active and selective immune-skewing gates in the steady state. Based on emerging knowledge of the central nervous system and information from other immune-privileged sites, we propose that these sites are endowed either with absolute endothelial-based barriers and epithelial gates that enable selective and educative transfer of trafficking leukocytes or with selective epithelial gates only.

Hypothalamic neuronal toll-like receptor 2 protects against age-induced obesity.

Toll-like receptors (TLRs) are traditionally associated with immune-mediated host defense. Here, we ascribe a novel extra-immune, hypothalamic-associated function to TLR2, a TLR-family member known to recognize lipid components, in the protection against obesity. We found that TLR2-deficient mice exhibited mature-onset obesity and susceptibility to high-fat diet (HFD)-induced weight gain, via modulation of food intake. Age-related obesity was still evident in chimeric mice, carrying comparable TLR2(+) immune cells, suggesting a non-hematopoietic-related involvement of this receptor. TLR2 was up-regulated with age or HFD in pro-opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus, a brain area participating in central-metabolic regulation, possibly modulating the hypothalamic-anorexigenic peptide, α-melanocyte-stimulating hormone (α-MSH). Direct activation of TLR2 in a hypothalamic-neuronal cell-line via its known ligands, further supports its capacity to mediate non-immune related metabolic regulation. Thus, our findings identify TLR2 expressed by hypothalamic neurons as a potential novel regulator of age-related weight gain and energy expenditure.

The retina as a window to the brain-from eye research to CNS disorders.

Philosophers defined the eye as a window to the soul long before scientists addressed this cliché to determine its scientific basis and clinical relevance. Anatomically and developmentally, the retina is known as an extension of the CNS; it consists of retinal ganglion cells, the axons of which form the optic nerve, whose fibres are, in effect, CNS axons. The eye has unique physical structures and a local array of surface molecules and cytokines, and is host to specialized immune responses similar to those in the brain and spinal cord. Several well-defined neurodegenerative conditions that affect the brain and spinal cord have manifestations in the eye, and ocular symptoms often precede conventional diagnosis of such CNS disorders. Furthermore, various eye-specific pathologies share characteristics of other CNS pathologies. In this Review, we summarize data that support examination of the eye as a noninvasive approach to the diagnosis of select CNS diseases, and the use of the eye as a valuable model to study the CNS. Translation of eye research to CNS disease, and deciphering the role of immune cells in these two systems, could improve our understanding and, potentially, the treatment of neurodegenerative disorders.

The privileged immunity of immune privileged organs: the case of the eye.

Understanding of ocular diseases and the search for their cure have been based on the common assumption that the eye is an immune privileged site, and the consequent conclusion that entry of immune cells to this organ is forbidden. Accordingly, it was assumed that when immune cell entry does occur, this reflects an undesired outcome of breached barriers. However, studies spanning more than a decade have demonstrated that acute insults to the retina, or chronic conditions resulting in retinal ganglion cell loss, such as in glaucoma, result in an inferior outcome in immunocompromised mice; likewise, steroidal treatment was found to be detrimental under these conditions. Moreover, even conditions that are associated with inflammation, such as age-related macular degeneration, are not currently believed to require immune suppression for treatment, but rather, are thought to benefit from immune modulation. Here, we propose that the immune privilege of the eye is its ability to enable, upon need, the entry of selected immune cells for its repair and healing, rather than to altogether prevent immune cell entry. The implications for acute and chronic degenerative diseases, as well as for infection and inflammatory diseases, are discussed.

The glial scar-monocyte interplay: a pivotal resolution phase in spinal cord repair.

The inflammatory response in the injured spinal cord, an immune privileged site, has been mainly associated with the poor prognosis. However, recent data demonstrated that, in fact, some leukocytes, namely monocytes, are pivotal for repair due to their alternative anti-inflammatory phenotype. Given the pro-inflammatory milieu within the traumatized spinal cord, known to skew monocytes towards a classical phenotype, a pertinent question is how parenchymal-invading monocytes acquire resolving properties essential for healing, under such unfavorable conditions. In light of the spatial association between resolving (interleukin (IL)-10 producing) monocytes and the glial scar matrix chondroitin sulfate proteoglycan (CSPG), in this study we examined the mutual relationship between these two components. By inhibiting the de novo production of CSPG following spinal cord injury, we demonstrated that this extracellular matrix, mainly known for its ability to inhibit axonal growth, serves as a critical template skewing the entering monocytes towards the resolving phenotype. In vitro cell culture studies demonstrated that this matrix alone is sufficient to induce such monocyte polarization. Reciprocal conditional ablation of the monocyte-derived macrophages concentrated at the lesion margins, using diphtheria toxin, revealed that these cells have scar matrix-resolving properties. Replenishment of monocytic cell populations to the ablated mice demonstrated that this extracellular remodeling ability of the infiltrating monocytes requires their expression of the matrix-degrading enzyme, matrix metalloproteinase 13 (MMP-13), a property that was found here to be crucial for functional recovery. Altogether, this study demonstrates that the glial scar-matrix, a known obstacle to regeneration, is a critical component skewing the encountering monocytes towards a resolving phenotype. In an apparent feedback loop, monocytes were found to regulate scar resolution. This cross-regulation between the glial scar and monocytes primes the resolution of this interim phase of spinal cord repair, thereby providing a fundamental platform for the dynamic healing response.

Neuroprotection and progenitor cell renewal in the injured adult murine retina requires healing monocyte-derived macrophages.

The death of retinal ganglion cells (RGCs) is a hallmark of many retinal neuropathies. Neuroprotection, axonal regeneration, and cell renewal are vital for the integrity of the visual system after insult but are scarce in the adult mammalian retina. We hypothesized that monocyte-derived macrophages, known to promote healing in peripheral tissues, are required after an insult to the visual system, where their role has been largely overlooked. We found that after glutamate eye intoxication, monocyte-derived macrophages infiltrated the damaged retina of mice. Inhibition of this infiltration resulted in reduced survival of RGCs and diminished numbers of proliferating retinal progenitor cells (RPCs) in the ciliary body. Enhancement of the circulating monocyte pool led to increased RGC survival and RPC renewal. The infiltrating monocyte-derived macrophages skewed the milieu of the injured retina toward an antiinflammatory and neuroprotective one and down-regulated accumulation of other immune cells, thereby resolving local inflammation. The beneficial effect on RGC survival depended on expression of interleukin 10 and major histocompatibility complex class II molecules by monocyte-derived macrophages. Thus, we attribute to infiltrating monocyte-derived macrophages a novel role in neuroprotection and progenitor cell renewal in the injured retina, with far-reaching potential implications to retinal neuropathies and other neurodegenerative disorders.

Immune maintenance in glaucoma: boosting the body's own neuroprotective potential.

Glaucoma, a slow progressive neurodegenerative disorder associated with death of retinal ganglion cells and degeneration of their connected optic nerve fibers, has been classically linked to high intraocular pressure. Regardless of the primary risk factor, degeneration may continue, resulting in further loss of neurons and subsequent glaucomatous damage. During the past decade, scientists and clinicians began to accept that, in addition or as an alternative to fighting off the primary risk factor(s), there is a need to protect the tissue from the ongoing spread of damage-an approach collectively termed "neuroprotection." We found that the immune system, the body's own defense mechanism, plays a key role in the ability of the optic nerve and the retina to withstand glaucomatous conditions. This defense involves recruitment of both innate and adaptive immune cells that together create a protective niche and thereby halt disease progression. The spontaneous immune response might not be sufficient, and therefore, we suggest boosting it by immunization (with the appropriate antigen, at specific timing and predetermined optimal dosing) which may be developed into a suitable therapeutic vaccination to treat glaucoma. This view of immune system involvement in glaucoma will raise new challenges in glaucoma research, changing the way in which clinicians perceive the disease and the approach to therapy.

Infiltrating blood-derived macrophages are vital cells playing an anti-inflammatory role in recovery from spinal cord injury in mice.

BACKGROUND: Although macrophages (MPhi) are known as essential players in wound healing, their contribution to recovery from spinal cord injury (SCI) is a subject of debate. The difficulties in distinguishing between different MPhi subpopulations at the lesion site have further contributed to the controversy and led to the common view of MPhi as functionally homogenous. Given the massive accumulation in the injured spinal cord of activated resident microglia, which are the native immune occupants of the central nervous system (CNS), the recruitment of additional infiltrating monocytes from the peripheral blood seems puzzling. A key question that remains is whether the infiltrating monocyte-derived MPhi contribute to repair, or represent an unavoidable detrimental response. The hypothesis of the current study is that a specific population of infiltrating monocyte-derived MPhi is functionally distinct from the inflammatory resident microglia and is essential for recovery from SCI. METHODS AND FINDINGS: We inflicted SCI in adult mice, and tested the effect of infiltrating monocyte-derived MPhi on the recovery process. Adoptive transfer experiments and bone marrow chimeras were used to functionally distinguish between the resident microglia and the infiltrating monocyte-derived MPhi. We followed the infiltration of the monocyte-derived MPhi to the injured site and characterized their spatial distribution and phenotype. Increasing the naïve monocyte pool by either adoptive transfer or CNS-specific vaccination resulted in a higher number of spontaneously recruited cells and improved recovery. Selective ablation of infiltrating monocyte-derived MPhi following SCI while sparing the resident microglia, using either antibody-mediated depletion or conditional ablation by diphtheria toxin, impaired recovery. Reconstitution of the peripheral blood with monocytes resistant to ablation restored the lost motor functions. Importantly, the infiltrating monocyte-derived MPhi displayed a local anti-inflammatory beneficial role, which was critically dependent upon their expression of interleukin 10. CONCLUSIONS: The results of this study attribute a novel anti-inflammatory role to a unique subset of infiltrating monocyte-derived MPhi in SCI recovery, which cannot be provided by the activated resident microglia. According to our results, limited recovery following SCI can be attributed in part to the inadequate, untimely, spontaneous recruitment of monocytes. This process is amenable to boosting either by active vaccination with a myelin-derived altered peptide ligand, which indicates involvement of adaptive immunity in monocyte recruitment, or by augmenting the naïve monocyte pool in the peripheral blood. Thus, our study sheds new light on the long-held debate regarding the contribution of MPhi to recovery from CNS injuries, and has potentially far-reaching therapeutic implications.

Erratum to: Immune maintenance in glaucoma: boosting the body's own neuroprotective potential.

Glaucoma, a slow progressive neurodegenerative disorder associated with death of retinal ganglion cells and degeneration of their connected optic nerve fibers, has been classically linked to high intraocular pressure. Regardless of the primary risk factor, degeneration may continue, resulting in further loss of neurons and subsequent glaucomatous damage. During the past decade, scientists and clinicians began to accept that, in addition or as an alternative to fighting off the primary risk factor(s), there is a need to protect the tissue from the ongoing spread of damage-an approach collectively termed "neuroprotection." We found that the immune system, the body's own defense mechanism, plays a key role in the ability of the optic nerve and the retina to withstand glaucomatous conditions. This defense involves recruitment of both innate and adaptive immune cells that together create a protective niche and thereby halt disease progression. The spontaneous immune response might not be sufficient, and therefore, we suggest boosting it by immunization (with the appropriate antigen, at specific timing and predetermined optimal dosing) which may be developed into a suitable therapeutic vaccination to treat glaucoma. This view of immune system involvement in glaucoma will raise new challenges in glaucoma research, changing the way in which clinicians perceive the disease and the approach to therapy.[This corrects the article on p. in vol. .].

Toll-like receptor 4 restricts retinal progenitor cell proliferation.

Retinal neurogenesis ceases by the early postnatal period, although retinal progenitor cells (RPCs) persist throughout life. In this study, we show that in the mammalian eye, the function of Toll-like receptor 4 (TLR4) extends beyond regulation of the innate immune response; it restricts RPC proliferation. In TLR4-deficient mice, enhanced proliferation of cells reminiscent of RPCs is evident during the early postnatal period. In vitro experiments demonstrate that TLR4 acts as an intrinsic regulator of RPC fate decision. Increased TLR4 expression in the eye correlates with the postnatal cessation of cell proliferation. However, deficient TLR4 expression is not sufficient to extend the proliferative period but rather contributes to resumption of proliferation in combination with growth factors. Proliferation in vivo is inhibited by both MyD88-dependent and -independent pathways, similar to the mechanisms activated by TLR4 in immune cells. Thus, our study attributes a novel role to TLR4 as a negative regulator of RPC proliferation.

Glaucoma as a neuropathy amenable to neuroprotection and immune manipulation.

Glaucoma, once thought as a single disease, is actually a group of diseases of the optic nerve involving loss of retinal ganglion cells. The process of cell death occurs in a characteristic pattern of optic neuropathy, a broad term for a certain pattern of damage to the optic nerve (the bundle of nerve fibers that carries information from the eye to the brain). Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness. Worldwide, it is estimated that about 66.8 million people have visual impairment as a result of glaucoma, with 6.7 million suffering from blindness.

Two faces of chondroitin sulfate proteoglycan in spinal cord repair: a role in microglia/macrophage activation.

BACKGROUND: Chondroitin sulfate proteoglycan (CSPG) is a major component of the glial scar. It is considered to be a major obstacle for central nervous system (CNS) recovery after injury, especially in light of its well-known activity in limiting axonal growth. Therefore, its degradation has become a key therapeutic goal in the field of CNS regeneration. Yet, the abundant de novo synthesis of CSPG in response to CNS injury is puzzling. This apparent dichotomy led us to hypothesize that CSPG plays a beneficial role in the repair process, which might have been previously overlooked because of nonoptimal regulation of its levels. This hypothesis is tested in the present study. METHODS AND FINDINGS: We inflicted spinal cord injury in adult mice and examined the effects of CSPG on the recovery process. We used xyloside to inhibit CSPG formation at different time points after the injury and analyzed the phenotype acquired by the microglia/macrophages in the lesion site. To distinguish between the resident microglia and infiltrating monocytes, we used chimeric mice whose bone marrow-derived myeloid cells expressed GFP. We found that CSPG plays a key role during the acute recovery stage after spinal cord injury in mice. Inhibition of CSPG synthesis immediately after injury impaired functional motor recovery and increased tissue loss. Using the chimeric mice we found that the immediate inhibition of CSPG production caused a dramatic effect on the spatial organization of the infiltrating myeloid cells around the lesion site, decreased insulin-like growth factor 1 (IGF-1) production by microglia/macrophages, and increased tumor necrosis factor alpha (TNF-alpha) levels. In contrast, delayed inhibition, allowing CSPG synthesis during the first 2 d following injury, with subsequent inhibition, improved recovery. Using in vitro studies, we showed that CSPG directly activated microglia/macrophages via the CD44 receptor and modulated neurotrophic factor secretion by these cells. CONCLUSIONS: Our results show that CSPG plays a pivotal role in the repair of injured spinal cord and in the recovery of motor function during the acute phase after the injury; CSPG spatially and temporally controls activity of infiltrating blood-borne monocytes and resident microglia. The distinction made in this study between the beneficial role of CSPG during the acute stage and its deleterious effect at later stages emphasizes the need to retain the endogenous potential of this molecule in repair by controlling its levels at different stages of post-injury repair.

Toll-like receptors modulate adult hippocampal neurogenesis.

Neurogenesis - the formation of new neurons in the adult brain - is considered to be one of the mechanisms by which the brain maintains its lifelong plasticity in response to extrinsic and intrinsic changes. The mechanisms underlying the regulation of neurogenesis are largely unknown. Here, we show that Toll-like receptors (TLRs), a family of highly conserved pattern-recognizing receptors involved in neural system development in Drosophila and innate immune activity in mammals, regulate adult hippocampal neurogenesis. We show that TLR2 and TLR4 are found on adult neural stem/progenitor cells (NPCs) and have distinct and opposing functions in NPC proliferation and differentiation both in vitro and in vivo. TLR2 deficiency in mice impaired hippocampal neurogenesis, whereas the absence of TLR4 resulted in enhanced proliferation and neuronal differentiation. In vitro studies further indicated that TLR2 and TLR4 directly modulated self-renewal and the cell-fate decision of NPCs. The activation of TLRs on the NPCs was mediated via MyD88 and induced PKCalpha/beta-dependent activation of the NF-kappaB signalling pathway. Thus, our study identified TLRs as players in adult neurogenesis and emphasizes their specified and diverse role in cell renewal.