Decreased Hepatic Functional Reserve Increases the Risk of Piperacillin/Tazobactam-Induced Abnormal Liver Enzyme Levels: A Retrospective Case-Control Study.

BACKGROUND: Piperacillin/tazobactam (PIPC/TAZ), which is a combination of a beta-lactam/beta-lactamase inhibitor, often causes liver enzyme abnormalities. The albumin-bilirubin (ALBI) score is a simple index that uses the serum albumin and total bilirubin levels for estimating hepatic functional reserve. Although patients with low hepatic reserve may be at high risk for drug-induced liver enzyme abnormalities, the relationship between PIPC/TAZ-induced abnormal liver enzymes levels and the ALBI score remains unknown. OBJECTIVE: This study aimed to elucidate the relationship between PIPC/TAZ-induced abnormal liver enzyme levels and the ALBI score. METHODS: This single-center retrospective case-control study included 335 patients. The primary outcome was PIPC/TAZ-induced abnormal liver enzyme levels. We performed COX regression analysis with male gender, age (≥75 years), alanine aminotransferase level (≥20 IU/L), and ALBI score (≥-2.00) as explanatory factors. To investigate the influence of the ALBI score on the development of abnormal liver enzyme levels, 1:1 propensity score matching between the ≤-2.00 and ≥-2.00 ALBI score groups was performed using the risk factors for drug-induced abnormal liver enzyme levels. RESULTS: The incidence of abnormal liver enzyme levels was 14.0% (47/335). COX regression analysis revealed that an ALBI score ≥-2.00 was an independent risk factor for PIPC/TAZ-induced abnormal liver enzyme levels (adjusted hazard ratio: 3.08, 95% coefficient interval: 1.207-7.835, P = 0.019). After 1:1 propensity score matching, the Kaplan-Meier curve revealed that the cumulative risk for PIPC/TAZ-induced abnormal liver enzyme levels was significantly higher in the ALBI score ≥-2.00 group (n = 76) than in the <-2.00 group (n = 76) (P = 0.033). CONCLUSION AND RELEVANCE: An ALBI score ≥-2.00 may predict the development of PIPC/TAZ-induced abnormal liver enzyme levels. Therefore, frequent monitoring of liver enzymes should be conducted to minimize the risk of severe PIPC/TAZ-induced abnormal liver enzyme levels in patients with low hepatic functional reserve.

Effect of Ceftriaxone Dosage and Albumin-Bilirubin Score on the Risk of Ceftriaxone-Induced Liver Injury.

The albumin-bilirubin (ALBI) score is an index of hepatic functional reserve and is calculated from serum albumin and total bilirubin levels. However, the relationship between ceftriaxone (CTRX)-induced liver injury and ALBI score remains unknown. Therefore, we aimed to elucidate the risk of CTRX-induced liver injury based on the ALBI scores and CTRX dosage. This was a single-center, retrospective, case-control study of 490 patients and the primary outcome was CTRX-induced liver injury. We performed a COX regression analysis using age ≥75 years, male sex, alanine aminotransferase levels, ALBI score, and CTRX dosage regimen (4 ≥2 or 1 g/d) as explanatory factors. We also performed 1 : 1 propensity score matching between non-liver injury and liver injury groups. The incidence of liver injury was 10.0% (49/490). In COX regression analysis, CTRX 4 g/d was an independent risk factor for liver injury (95% coefficient interval: 1.05-6.96, p = 0.04). Meanwhile, ALBI score ≥-1.61 was an independent factor for liver injury (95% coefficient interval: 1.03-3.22, p = 0.04) with the explanatory factor of ≥2 and 1 g/d. The Kaplan-Meier curve indicated that the cumulative risk for CTRX-induced liver injury was significantly higher in the ALBI score ≥-1.61 group than in the ALBI score <-1.61 group before propensity score matching (p = 0.032); however, no significant differences were observed after propensity score matching (p = 0.791). These findings suggest that in patients treated with CTRX with ALBI score ≥-1.61, frequent liver function monitoring should be considered.

TC10, a Rho family GTPase, is required for efficient axon regeneration in a neuron-autonomous manner.

Intracellular signaling pathways that promote axon regeneration are closely linked to the mechanism of neurite outgrowth. TC10, a signaling molecule that acts on neurite outgrowth through membrane transport, is a member of the Rho family G proteins. Axon injury increases the TC10 levels in motor neurons, suggesting that TC10 may be involved in axon regeneration. In this study, we tried to understand the roles of TC10 in the nervous system using TC10 knock-out mice. In cultured hippocampal neurons, TC10 ablation significantly reduced axon elongation without affecting ordinary polarization. We determined a role of TC10 in microtubule stabilization at the growth cone neck; therefore, we assume that TC10 limits axon retraction and promotes in vitro axon outgrowth. In addition, there were no notable differences in the size and structure of brains during prenatal and postnatal development between wild-type and TC10 knock-out mice. In motor neurons, axon regeneration after injury was strongly suppressed in mice lacking TC10 (both in conventional and injured nerve specific deletion). In retinal ganglion cells, TC10 ablation suppressed the axon regeneration stimulated by intraocular inflammation and cAMP after optic nerve crush. These results show that TC10 plays an important role in axon regeneration in both the peripheral and central nervous systems, and the role of TC10 in peripheral axon regeneration is neuron-intrinsic.

A novel activation mechanism of cellular Factor XIII in zebrafish retina after optic nerve injury.

Cellular Factor XIII (cFXIII) mRNA is rapidly upregulated in the fish retina after optic nerve injury (ONI). Here, we investigated the molecular mechanism of cFXIII gene activation using genetic information from the A-subunit of cFXIII (cFXIII-A). Real-time PCR that amplified the active site (exons 7-8) of cFXIII-A showed increased cFXIII-A mRNA in the retina after ONI, whereas the PCR that amplified the activation peptide (exons 1-2) showed no change. RT-PCR analysis that amplified exons 1-8 showed two bands, a faint long band in the control retina and a dense short band in the injured retina. Therefore, we conclude that activated cFXIII-A mRNA after ONI is shorter than that of the control retina. Western blot analysis also confirmed an active form of 65 kDa cFXIII-A protein in the injured retina compared to the control 84 kDa protein. 5'-RACE analysis using injured retina revealed that the short cFXIII-A mRNA lacked exons 1, 2 and part of exon 3. Exon 3 has two sites of heat shock factor 1 (HSF-1) binding consensus sequence. Intraocular injection of HSF inhibitor suppressed the expression of cFXIII-A mRNA in the retina 1 day after ONI to 40% of levels normally seen after ONI. Chromatin immunoprecipitation provides direct evidence of enrichment of cFXIII-A genomic DNA bound with HSF-1. The present data indicate that rapid HSF-1 binding to the cFXIII-A gene results in cleavage of activation peptide and an active form of short cFXIII-A mRNA and protein in the zebrafish retina after ONI without thrombin.

S-Nitrosylation Regulates Cell Survival and Death in the Central Nervous System.

Nitric oxide (NO), which is produced from nitric oxide synthase, is an important cell signaling molecule that is crucial for many physiological functions such as neuronal death, neuronal survival, synaptic plasticity, and vascular homeostasis. This diffusible gaseous compound functions as an effector or second messenger in many intercellular communications and/or cell signaling pathways. Protein S-nitrosylation is a posttranslational modification that involves the covalent attachment of an NO group to the thiol side chain of select cysteine residues on target proteins. This process is thought to be very important for the regulation of cell death, cell survival, and gene expression in the central nervous system (CNS). However, there have been few reports on the role of protein S-nitrosylation in CNS disorders. Here, we briefly review specific examples of S-nitrosylation, with particular emphasis on its functions in neuronal cell death and survival. An understanding of the role and mechanisms underlying the effects of protein S-nitrosylation on neurodegenerative/neuroprotective events may reveal a novel therapeutic strategy for rescuing neurons in neurodegenerative diseases.

Protein Carbonylation-Dependent Photoreceptor Cell Death Induced by N-Methyl-N-nitrosourea in Mice.

Retinal degenerative diseases, such as retinitis pigmentosa, are characterized by night blindness and peripheral vision loss caused by the slowly progressive loss of photoreceptor cells. A comprehensive molecular mechanism of the photoreceptor cell death remains unclear. We previously reported that heat shock protein 70 (HSP70), which has a protective effect on neuronal cells, was cleaved by a calcium-dependent protease, calpain, in N-methyl-N-nitrosourea (MNU)-treated mice retina. Carbonylated HSP70 is much more vulnerable than noncarbonylated HSP70 to calpain cleavage. However, it was not known whether protein carbonylation occurs in MNU-treated mice retina. In this study, we clearly show protein carbonylation-dependent photoreceptor cell death induced by MNU in mice. Therefore, protein carbonylation and subsequent calpain-dependent cleavage of HSP70 are key events in MNU-mediated photoreceptor cell death. Our data provide a comprehensive molecular mechanism of the photoreceptor cell death.

Alternative Splicing for Activation of Coagulation Factor XIII-A in the Fish Retina After Optic Nerve Injury.

Factor XIII-A (FXIII-A), which has become known as cellular transglutaminase, plays important roles in mediating cross-linking reactions in various tissues. FXIII-A acts as one of the regeneration molecules in the fish retina and optic nerve after optic nerve injury and becomes activated at the site of injury within a few hours. Previous research has shown that activated FXIII-A induces neurite outgrowth from injured retinal ganglion cells and supports elongation of the regenerating optic nerve. However, the activation mechanism of FXIII-A remains unknown. Furthermore, the injured tissues do not express thrombin, a known activator of plasma FXIII. Here, we investigated the mRNA expression of FXIII-A based on two different regions, one encoding the activation peptide and the other encoding the enzymatic active site. We found that expression of the region encoding the activation peptide was markedly suppressed compared with the region encoding the active site. An overexpression study with a short-type FXIII-A cDNA lacking the activation peptide revealed induction of long neurite outgrowth in fish retinal explant cultures compared with full-length FXIII-A cDNA. The present findings suggest that alternative splicing may occur in the FXIII-A gene, resulting in deletion of the region encoding the activation peptide and thus allowing direct production of activated FXIII-A protein in the fish retina and optic nerve after optic nerve injury.

Talaumidin Promotes Neurite Outgrowth of Staurosporine-Differentiated RGC-5 Cells Through PI3K/Akt-Dependent Pathways.

Talaumidin, a tetrahydrofuran neolignan isolated from the root of Aristolochia arcuata, was an interesting small molecule with neurotrophic activity in the cultured neuron. Talaumidin can promote neurite outgrowth from neurons. However, the mechanism by which talaumidin exerts its neurotrophic actions on retinal neurons has not been elucidated to date. In this study, we describe that talaumidin has neurotrophic properties such as neurite outgrowth in neuroretinal cell line, RGC-5. Talaumidin promotes staurosporine-induced neurite outgrowth in RGC-5 cells. The neurite outgrowth effect of talaumidin was inhibited by phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, but not by Erk inhibitor, PD98059. These data suggest that talaumidin promotes neurite outgrowth through PI3K/Akt pathway and that the potential of talaumidin serves as a promising lead compound for the treatment of retinal degenerative disorders.

A novel function of neuroglobin for neuroregeneration in mice after optic nerve injury.

Neuroglobin (Ngb) is a recently discovered heme protein in the vertebrate brain that can bind to oxygen molecules. Mammalian Ngb plays a crucial role in neuroprotection under conditions of oxidative stress. To investigate other potential functions of Ngb, we investigated the mouse retinal Ngb system following optic nerve injury. In the retina of control mice, Ngb immunoreactivity was limited to the retinal ganglion cell (RGC) layer, and this immunoreactivity rapidly decreased to less than 50% of the control level 5 days after optic nerve injury. On the basis of this decrease, we designed in vivo experiments with enhanced expression of Ngb using adult mouse retina. The enhanced expression of Ngb was achieved by injecting chimeric human Ngb protein, which included the cell membrane-penetrating module of fish Ngb. One-day pretreatment with chimeric Ngb increased immunoreactivity levels of Ngb two-fold in mouse RGCs and increased the number of surviving RGCs three-fold by 14 days after optic nerve injury compared with vehicle controls. Furthermore, in the mouse retinas showing enhanced Ngb expression, several regenerating central optic axons exhibited outgrowth and were found to pass through the nerve crush site 14 days after nerve injury. No such regenerating optic axons were observed in the control mouse optic nerve during the same time frame. The data obtained from in vivo experiments strongly indicate that mammalian Ngb has neuroprotective and neuroregenerative properties.

Geranylgeranylacetone Suppresses N-Methyl-N-nitrosourea-Induced Photoreceptor Cell Loss in Mice.

Retinitis pigmentosa is a disease characterized by the loss of photoreceptor cells. The N-methyl-N-nitrosourea (MNU)-induced retinal degeneration model is widely used to study the mechanism of these retinal degenerative disorders because of its selective photoreceptor cell death. As for the cell death mechanism of MNU, calcium-calpain activation and lipid peroxidation processes are involved in the initiation of this cell death. Although such molecular mechanisms of the MNU-induced cell death have been described, the total image of the cell death is still obscure. Heat shock protein 70 (HSP70) has been shown to function as a chaperon molecule to protect cells against environmental and physiological stresses. In this study, we investigated the effect of geranylgeranylacetone (GGA), an accylic polyisoprenoid, on MNU-induced photoreceptor cell loss. HSP70 induction by GGA was effective against MNU-induced photoreceptor cell loss as a result of its ability to prevent HSP70 degradation. The data indicate that GGA may help to suppress the onset and progression of retinitis pigmentosa.

Nitric Oxide Synthase Activation as a Trigger of N-methyl-N-nitrosourea-Induced Photoreceptor Cell Death.

Retinal degeneration (RD) such as retinitis pigmentosa and age-related macular degeneration are major causes of blindness in adulthood. As one of the model for RD, intraperitoneal injection of N-methyl-N-nitrosourea (MNU) is widely used because of its selective photoreceptor cell death. It has been reported that MNU increases intracellular calcium ions in the retina and induces photoreceptor cell death. Although calcium ion influx triggers the neuronal nitric oxide synthase (nNOS) activation, the role of nNOS on photoreceptor cell death by MNU has not been reported yet. In this study, we investigated the contribution of nNOS on photoreceptor cell death induced by MNU in mice. MNU significantly increased NOS activation at 3 day after treatment. Then, we evaluated the effect of nNOS specific inhibitor, ethyl[4-(trifluoromethyl) phenyl]carbamimidothioate (ETPI) on the MNU-induced photoreceptor cell death. At 3 days, ETPI clearly inhibited the MNU-induced cell death in the ONL. These data indicate that nNOS is a key molecule for pathogenesis of MNU-induced photoreceptor cell death.

Cell Fate of Müller Cells During Photoreceptor Regeneration in an N-Methyl-N-nitrosourea-Induced Retinal Degeneration Model of Zebrafish.

Zebrafish can regenerate several organs such as the tail fin, heart, central nervous system, and photoreceptors. Very recently, a study has demonstrated the photoreceptor regeneration in the alkylating agent N-methyl-N-nitrosourea (MNU)-induced retinal degeneration (RD) zebrafish model, in which whole photoreceptors are lost within a week after MNU treatment and then regenerated within a month. The research has also shown massive proliferation of Müller cells within a week. To address the question of whether proliferating Müller cells are the source of regenerating photoreceptors, which remains unknown in the MNU-induced zebrafish RD model, we employed a BrdU pulse-chase technique to label the proliferating cells within a week after MNU treatment. As a result of the BrdU pulse-chase technique, a number of BrdU(+) cells were observed in the outer nuclear layer as well as the inner nuclear layer. This implies that regenerating photoreceptors are derived from proliferating Müller cells in the zebrafish MNU-induced RD model.

A Possible Role of Neuroglobin in the Retina After Optic Nerve Injury: A Comparative Study of Zebrafish and Mouse Retina.

Neuroglobin (Ngb) is a new member of the family of heme proteins and is specifically expressed in neurons of the central and peripheral nervous systems in all vertebrates. In particular, the retina has a 100-fold higher concentration of Ngb than do other nervous tissues. The role of Ngb in the retina is yet to be clarified. Therefore, to understand the functional role of Ngb in the retina after optic nerve injury (ONI), we used two types of retina, from zebrafish and mice, which have permissible and non-permissible capacity for nerve regeneration after ONI, respectively. After ONI, the Ngb protein in zebrafish was upregulated in the amacrine cells within 3 days, whereas in the mouse retina, Ngb was downregulated in the retinal ganglion cells (RGCs) within 3 days. Zebrafish Ngb (z-Ngb) significantly enhanced neurite outgrowth in retinal explant culture. According to these results, we designed an overexpression experiment with the mouse Ngb (m-Ngb) gene in RGC-5 cells (retinal precursor cells). The excess of m-Ngb actually rescued RGC-5 cells under hypoxic conditions and significantly enhanced neurite outgrowth in cell culture. These data suggest that mammalian Ngb has positive neuroprotective and neuritogenic effects that induce nerve regeneration after ONI.

Involvement of neuronal nitric oxide synthase in N-methyl-N-nitrosourea-induced retinal degeneration in mice.

N-methyl-N-nitrosourea (MNU) is widely used to study the mechanism of retinal degenerative diseases (RDs) because of its selectivity of photoreceptor cell death. Many reports suggest that excessive nitric oxide (NO) plays a crucial role in neuronal cell death. We hypothesized that nitric oxide synthase (NOS)/NO are involved in photoreceptor cell death by MNU. We found that the levels of NO increased after MNU treatment. Furthermore, we demonstrated that neuronal NOS specific inhibitor attenuated photoreceptor cell death by MNU in mice. We believe that our findings might be a new target for the treatment of RDs.

Full-length axon regeneration in the adult mouse optic nerve and partial recovery of simple visual behaviors.

The mature optic nerve cannot regenerate when injured, leaving victims of traumatic nerve damage or diseases such as glaucoma with irreversible visual losses. Recent studies have identified ways to stimulate retinal ganglion cells to regenerate axons part-way through the optic nerve, but it remains unknown whether mature axons can reenter the brain, navigate to appropriate target areas, or restore vision. We show here that with adequate stimulation, retinal ganglion cells are able to regenerate axons the full length of the visual pathway and on into the lateral geniculate nucleus, superior colliculus, and other visual centers. Regeneration partially restores the optomotor response, depth perception, and circadian photoentrainment, demonstrating the feasibility of reconstructing central circuitry for vision after optic nerve damage in mature mammals.

Heat shock protein 70 induction by valproic acid delays photoreceptor cell death by N-methyl-N-nitrosourea in mice.

Retinal degenerative diseases (RDs) are a group of inherited diseases characterized by the loss of photoreceptor cells. Selective photoreceptor loss can be induced in mice by an intraperitoneal injection of N-methyl-N-nitrosourea (MNU) and, because of its selectivity, this model is widely used to study the mechanism of RDs. Although it is known that calcium-calpain activation and lipid peroxidation are involved in the initiation of cell death, the precise mechanisms of this process remain unknown. Heat shock protein 70 (HSP70) has been shown to function as a chaperone molecule to protect cells against environmental and physiological stresses. In this study, we investigated the role of HSP70 on photoreceptor cell death in mice. HSP70 induction by valproic acid, a histone deacetylase inhibitor, attenuated the photoreceptor cell death by MNU through inhibition of apoptotic caspase signals. Furthermore, HSP70 itself was rapidly and calpain-dependently cleaved after MNU treatment. Therefore, HSP70 induction by valproic acid was dually effective against MNU-induced photoreceptor cell loss as a result of its anti-apoptotic actions and its ability to prevent HSP70 degradation. These findings might help lead us to a better understanding of the pathogenic mechanism of RDs. Retinal degenerative diseases are characterized by the loss of photoreceptor cells. We proposed the following cascade for N-methyl-N-nitrosourea (MNU)-induced photoreceptor cell death: MNU gives rise to cleavage of heat shock protein 70 (HSP70); HSP70 induction by valproic acid (VPA) is dually effective against MNU-induced photoreceptor cell loss because of its anti-apoptotic actions and its ability to prevent HSP70 degradation. We hope that the present study heralds a new era in developing therapeutic tools against retinal degenerative diseases.

Neuritogenic activity of trichostatin A in adult rat retinal ganglion cells through acetylation of histone H3 lysine 9 and RARß induction.

Like other CNS neurons, mature retinal ganglion cells (RGCs) cannot regenerate their axons after nerve injury due to loss of regenerative capacity. One of the reasons why they lose their capacity seems to be a dramatic shift in gene expression of RGCs under epigenetic modulation. In here, we found that levels of histone H3 lysine 9 acetylation decreased after birth in RGCs. This decrease showed good correlation with restriction of retinoic acid receptor ß (RARß) expression in RGCs after birth. Furthermore, we demonstrated that a histone deacetylase inhibitor, trichostatin A, induced axonal regeneration of adult rat RGCs through RARß induction.

Reciprocal changes in factor XIII and retinal transglutaminase expressions in the fish retina during optic nerve regeneration.

Unlike mammals, fish retinal ganglion cells have the capacity to repair their axons even after optic nerve transection. In the process of fish optic nerve regeneration, a large number of genes have been described as regeneration-associated molecules. Using molecular cloning techniques, we identified two types of cDNA clones belonging to the transglutaminase (TG) family which were upregulation genes; one is cellular factor XIII (cFXIII) and the other is a tissue type TG named retinal transglutaminase (TGR). cFXIII mRNA started to increase in the retinal ganglion cells at 1-2 days, peaked at 5-7 days, and returned to the control level by 20 days post optic nerve injury. In contrast, TGR mRNA started to increase at day 5-10, peaked at day 20, and then gradually decreased by day 40 after nerve injury. To elucidate the molecular involvement of these TGs in optic nerve regeneration, we studied the effects of recombinant TGR protein or overexpression of cFXIII using a retinal explant culture system. cFXIII effectively induced neurite outgrowth only from naïve (intact) retinas. In contrast, the TGR protein significantly enhanced neurite outgrowth only from primed retinas, in which the optic nerve had been crushed 5-7 days previously. These reciprocal expressions of cFXIII and TGR suggest that these two types of TGs are important for the neurite sprouting and axonal elongation processes, respectively, during optic nerve regeneration processes.

Nipradilol promotes axon regeneration through S-nitrosylation of PTEN in retinal ganglion cells.

Nipradilol (Nip) is registered as an anti-glaucoma agent. More recently, a protective effect of Nip has been demonstrated in retinal ganglion cells (RGCs) mediated by S-nitrosylation of antioxidative-related Keap1 protein due to its nitric oxide (NO)-donating effect. It also has been reported that Nip promoted axon outgrowth in cat RGCs. However, the detailed mechanism remains unclear. NO physiologically regulates numerous cellular responses through S-nitrosylation of protein at cysteine residues. It has been reported that phosphatase and tensin homologue deleted on chromosome 10 (PTEN) deletion strongly showed axon regeneration after optic nerve injury. PTEN inactivation by S-nitrosylation results in the accumulation of phosphatidylinositol (3, 4, 5) triphosphate (PIP3) and the activation of Akt/mammalian target of rapamycin (mTOR) signaling. The ribosomal S6 kinase 1 (S6K) which can monitor as phospho-S6 (pS6) is one of major target of mTOR. In this study, we investigated the possibility that Nip can promote axon outgrowth in RGCs by Akt/mTOR signaling thorough S-nitrosylation of PTEN.

Regeneration-associated genes on optic nerve regeneration in fish retina.

It has been well documented that fish central nervous system, including retina and optic nerve, can regenerate and recover its function after nerve injury. Within a few decades, a number of regeneration-associated genes (RAGs) have been identified in fish retina following optic nerve injury (ONI). RAGs can be classified into two groups: cell survival- and axonal outgrowth-related genes. In fish retina after ONI, cell survival-related genes were upregulated in 1-6 days after ONI, which corresponds to the preparation stage for cell survival and axonal sprouting. Subsequently, axonal outgrowth-related genes were upregulated in 1-6 weeks after ONI, which corresponds to the axonal regrowth stage. Recently, we've found a novel type of RAGs, dedifferentiation-related genes, that are upregulated in overlapping time between cell survival and axonal regrowth (3-10 days after ONI). In this chapter we summarize these three types of RAGs that promote optic nerve regeneration in the fish retina after ONI.