A novel combination approach to effectively reduce inflammation and neurodegeneration in multiple sclerosis models.

Multiple sclerosis (MS) is an autoimmune disease characterized by immune-mediated attacks on the central nervous system (CNS), resulting in demyelination and recurring T-cell responses. Unfortunately, there is no cure for it. Current therapies that target immunomodulation and/or immunosuppression show only modest beneficial effects, have many side effects, and do not block neurodegeneration or progression of the disease. Since neurodegeneration and in particular axonal degeneration is implicated in disability in progressive MS, development of novel therapeutic strategies to attenuate the neurodegenerative processes is imperative. This study aims to develop new safe and efficacious treatments that address both the inflammatory and neurodegenerative aspects of MS using its animal model, experimental allergic encephalomyelitis (EAE). In EAE, the cysteine protease calpain is upregulated in CNS tissue, and its activity correlates with neurodegeneration. Our immunologic studies on MS have indicated that increased calpain activity promotes pro-inflammatory T helper (Th)1 cells and the severity of the disease in EAE, suggesting that calpain inhibition could be a novel target to combat neurodegeneration in MS/EAE. While calpain inhibition by SNJ1945 reduced disease severity, treatment of EAE animals with a novel protease-resistant altered small peptide ligand (3aza-APL) that mimic myelin basic protein (MBP), also decreased the incidence of EAE, disease severity, infiltration of inflammatory cells, and protected myelin. A reduction in inflammatory T-cells with an increase in Tregs and myeloid suppressor cells is also found in EAE mice treated with SNJ1945 and 3aza-APL. Thus, a novel combination strategy was tested in chronic EAE mouse model in B10 mice which showed multiple pathological mechanisms could be addressed by simultaneous treatment with calpain inhibitor SNJ1945 and protease-resistant 3aza-APL to achieve a stronger therapeutic effect.

A Nanocurcumin and Pyrroloquinoline Quinone Formulation Prevents Hypobaric Hypoxia-Induced Skeletal Muscle Atrophy by Modulating NF-κB Signaling Pathway.

Kushwaha, Asha D., and Deepika Saraswat. A nanocurcumin and pyrroloquinoline quinone formulation prevents hypobaric hypoxia-induced skeletal muscle atrophy by modulating NF-κB signaling pathway. High Alt Med Biol. 23:249-263, 2022. Background: Hypobaric hypoxia (HH)-induced deleterious skeletal muscle damage depends on exposure time and availability of oxygen at cellular level, which eventually can limit human work performance at high altitude (HA). Despite the advancements made in pharmacological (performance enhancer, antioxidants) and nonpharmacological therapeutics (acclimatization strategies), only partial success has been achieved in improving physical performance at HA. A distinctive combination of nanocurcumin (NC) and pyrroloquinoline quinone (PQQ) has been formulated (named NCF [nanocurcumin formulation], Indian patent No. 302877) in our laboratory, and has proven very promising in improving cardiomyocyte adaptation to chronic HH. We hypothesized that NCF might improve skeletal muscle adaptation and could be a performance enhancer at HA. Material and Methods: Adult Sprague-Dawley rats (220 ± 10 g) were divided into five groups (n = 6/group): normoxia vehicle control, hypoxia vehicle control, hypoxia NCF, hypoxia NC, and hypoxia PQQ. All the animals (except those in normoxia) were exposed to simulated HH in a chamber at temperature 22°C ± 2°C, humidity 50% ± 5%, altitude 25,000 ft for 1, 3, or 7 days. After completion of the stipulated exposure time, gastrocnemius and soleus muscles were excised from animals for further analysis. Results: Greater lengths of hypoxic exposure caused progressively increased muscle ring finger-1 (MuRF-1; p < 0.01) expression and calpain activation (0.56 ± 0.05 vs. 0.13 ± 0.02 and 0.44 ± 0.03 vs. 0.12 ± 0.021) by day 7, respectively in the gastrocnemius and soleus muscles. Myosin heavy chain type I (slow oxidative) fibers significantly (p > 0.01) decreased in gastrocnemius (>50%) and soleus (>46%) muscles by the seventh day of exposure. NCF supplementation showed (p ≤ 0.05) tremendous improvement in skeletal muscle acclimatization through effective alleviation of oxidative damage, and changes in calpain activity and atrophic markers at HA compared with hypoxia control or treatment alone with NC/PQQ. Conclusion: Thus, NCF-mediated anti-oxidative, anti-inflammatory effects lead to decreased proteolysis resulting in mitigated skeletal muscle atrophy under HH.

Inherited Retinal Degeneration: PARP-Dependent Activation of Calpain Requires CNG Channel Activity.

Inherited retinal degenerations (IRDs) are a group of blinding diseases, typically involving a progressive loss of photoreceptors. The IRD pathology is often based on an accumulation of cGMP in photoreceptors and associated with the excessive activation of calpain and poly (ADP-ribose) polymerase (PARP). Inhibitors of calpain or PARP have shown promise in preventing photoreceptor cell death, yet the relationship between these enzymes remains unclear. To explore this further, organotypic retinal explant cultures derived from wild-type and IRD-mutant mice were treated with inhibitors specific for calpain, PARP, and voltage-gated Ca2+ channels (VGCCs). The outcomes were assessed using in situ activity assays for calpain and PARP and immunostaining for activated calpain-2, poly (ADP-ribose), and cGMP, as well as the TUNEL assay for cell death detection. The IRD models included the Pde6b-mutant rd1 mouse and rd1*Cngb1-/- double-mutant mice, which lack the beta subunit of the rod cyclic nucleotide-gated (CNG) channel and are partially protected from rd1 degeneration. We confirmed that an inhibition of either calpain or PARP reduces photoreceptor cell death in rd1 retina. However, while the activity of calpain was decreased by the inhibition of PARP, calpain inhibition did not alter the PARP activity. A combination treatment with calpain and PARP inhibitors did not synergistically reduce cell death. In the slow degeneration of rd1*Cngb1-/- double mutant, VGCC inhibition delayed photoreceptor cell death, while PARP inhibition did not. Our results indicate that PARP acts upstream of calpain and that both are part of the same degenerative pathway in Pde6b-dependent photoreceptor degeneration. While PARP activation may be associated with CNG channel activity, calpain activation is linked to VGCC opening. Overall, our data highlights PARP as a target for therapeutic interventions in IRD-type diseases.

Occlusive retinal vasculitis: novel insights into causes, pathogenesis and treatment.

PURPOSE OF REVIEW: Occlusive retinal vasculitis (ORV) has a large differential diagnosis and varied therapeutic approaches. This review highlights existing and novel causes and treatment options for ORV. RECENT FINDINGS: Mutations in CAPN5, TREX1, and TNFAIP3 have been associated with dominantly inherited forms of ORV. Various intraocular therapeutics have been shown to occasionally cause ORV; the most recent medications associated with ORV are vancomycin and brolucizumab. In cases of ORV linked to Behçet's disease, clinical trials support the use of tumor necrosis factor alpha inhibitors. SUMMARY: Identification of the underlying etiology of ORV is critical to help guide treatment. Treatment in ORV involves both treatment any underlying infection or autoimmune condition, cessation of the any offending causative agent and local treatment of neovascular complications.

Titin splicing regulates cardiotoxicity associated with calpain 3 gene therapy for limb-girdle muscular dystrophy type 2A.

Limb-girdle muscular dystrophy type 2A (LGMD2A or LGMDR1) is a neuromuscular disorder caused by mutations in the calpain 3 gene (CAPN3). Previous experiments using adeno-associated viral (AAV) vector-mediated calpain 3 gene transfer in mice indicated cardiac toxicity associated with the ectopic expression of the calpain 3 transgene. Here, we performed a preliminary dose study in a severe double-knockout mouse model deficient in calpain 3 and dysferlin. We evaluated safety and biodistribution of AAV9-desmin-hCAPN3 vector administration to nonhuman primates (NHPs) with a dose of 3 × 1013 viral genomes/kg. Vector administration did not lead to observable adverse effects or to detectable toxicity in NHP. Of note, the transgene expression did not produce any abnormal changes in cardiac morphology or function of injected animals while reaching therapeutic expression in skeletal muscle. Additional investigation on the underlying causes of cardiac toxicity observed after gene transfer in mice and the role of titin in this phenomenon suggest species-specific titin splicing. Mice have a reduced capacity for buffering calpain 3 activity compared to NHPs and humans. Our studies highlight a complex interplay between calpain 3 and titin binding sites and demonstrate an effective and safe profile for systemic calpain 3 vector delivery in NHP, providing critical support for the clinical potential of calpain 3 gene therapy in humans.

Calpain-1 and Calpain-2 in the Brain: Dr. Jekill and Mr Hyde?

While the calpain system has now been discovered for over 50 years, there is still a paucity of information regarding the organization and functions of the signaling pathways regulated by these proteases, although calpains play critical roles in many cell functions. Moreover, calpain overactivation has been shown to be involved in numerous diseases. Among the 15 calpain isoforms identified, calpain-1 (aka µ-calpain) and calpain-2 (aka m-calpain) are ubiquitously distributed in most tissues and organs, including the brain. We have recently proposed that calpain-1 and calpain- 2 play opposite functions in the brain, with calpain-1 activation being required for triggering synaptic plasticity and neuroprotection (Dr. Jekill), and calpain-2 limiting the extent of plasticity and being neurodegenerative (Mr. Hyde). Calpain-mediated cleavage has been observed in cytoskeleton proteins, membrane-associated proteins, receptors/channels, scaffolding/anchoring proteins, and protein kinases and phosphatases. This review will focus on the signaling pathways related to local protein synthesis, cytoskeleton regulation and neuronal survival/death regulated by calpain-1 and calpain-2, in an attempt to explain the origin of the opposite functions of these 2 calpain isoforms. This will be followed by a discussion of the potential therapeutic applications of selective regulators of these 2 calpain isoforms.

Taurine Attenuates Calpain-2 Induction and a Series of Cell Damage via Suppression of NOX-Derived ROS in ARPE-19 Cells.

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) are key transmembrane proteins leading to reactive oxygen species (ROS) overproduction. However, the detailed roles of NOXs in retinal pigment epithelial (RPE) cell metabolic stress induced by Earle's balanced salt solution (EBSS) through starvation remain unclear. In this study, we investigated what roles NOXs play in regard to calpain activity, endoplasmic stress (ER), autophagy, and apoptosis during metabolic stress in ARPE-19 cells. We first found that EBSS induced an increase in NOX2, NOX4, p22phox, and NOX5 compared to NOX1. Secondly, suppression of NOXs resulted in reduced ER stress and autophagy, decreased ROS generation, and alleviated cell apoptosis. Thirdly, silencing of NOX4, NOX5, and p22phox resulted in reduced levels of cell damage. However, silencing of NOX1 was unaffected. Finally, taurine critically mediated NOXs in response to EBSS stress. In conclusion, this study demonstrated for the first time that NOX oxidases are the upstream regulators of calpain-2, ER stress, autophagy, and apoptosis. Furthermore, the protective effect of taurine is mediated by the reduction of NOX-derived ROS, leading to sequential suppression of calpain induction, ER stress, autophagy, and apoptosis.

[Role of Heat Shock Protein 70 in Retinitis Pigmentosa and a Novel Strategy for Treatment].

Retinitis pigmentosa (RP) is a group of inherited disorders involving the photoreceptors of the retina and can lead to visual loss. There has been tremendous progress in the delineation of the biochemical and molecular basis of RP. Reactive oxygen species, calcium-calpain activation, and lipid peroxidation are known to be involved in the initiation of photoreceptor cell death, but the precise mechanisms of this process remain unknown. Heat shock protein 70 (HSP70) has been shown to function as a chaperone molecule that protects cells against environmental and physiological stresses. However, there are a few reports showing the role of HSP70 in photoreceptor cell death. Recently, we found that the production of 4-hydroxy-2-noneral caused the calpain-dependent cleavage of carbonylated HSP70 prior to photoreceptor cell death in RP model mice. Furthermore, HSP70 inducers, such as valproic acid and geranylgeranylacetone attenuated photoreceptor cell death. HSP70 inducers may be considered as candidate therapeutic agents for RP.

A novel calpastatin-based inhibitor improves postischemic neurological recovery.

Calpastatin, a naturally occurring protein, is the only inhibitor that is specific for calpain. A novel blood-brain barrier (BBB)-permeant calpastatin-based calpain inhibitor, named B27-HYD, was developed and used to assess calpain's contribution to neurological dysfunction after stroke in rats. Postischemic administration of B27-HYD reduced infarct volume and neurological deficits by 35% and 44%, respectively, compared to untreated animals. We also show that the pharmacologic intervention has engaged the intended biologic target. Our data further demonstrates the potential utility of SBDP145, a signature biomarker of acute brain injury, in evaluating possible mechanisms of calpain in the pathogenesis of stroke and as an adjunct in guiding therapeutic decision making.

[Protective effect of calpain inhibitor-3 on hypoxic-ischemic brain damage of neonatal rats].

OBJECTIVE: The mechanisms of hypoxic-ischemic brain damage (HIBD) are still largely unknown. Elevation of intracellular calcium concentration and subsequent calcium-dependent proteases activation such as calpains seem to play an important role in the process of neuronal death. Calpain inhibitors showed neuroprotective effects in adult rat cerebral ischemia models. This study aimed to investigate the protective effect and associated mechanisms of calpain inhibitor-3 (MDL28170) on HIBD of neonatal rats. METHODS: Seven-day old Sprague-Dawley rats were randomly divided into three groups: the control group (n = 18), HIBD group (n = 48) and calpain inhibitor-3 treated group (MDL group, n = 48). The mice in the latter two groups were subjected to hypoxia-ischemia (HI) insult. The puppies in MDL group were intraperitoneally injected with MDL28170 (25 mg/kg) at 0, 2 and 4 h after HI, while those in the other two groups were intraperitoneally injected with normal saline instead. All the pupies were sacrificed at 6 h, 24 h and 72 h after HI. Quantitative real-time fluorescent polymerase chain reaction was employed to detect micro-calpain gene expression, immunoblotting technique was used to measure mu-calpain and caspase-3 protein activation, apoptosis of ipsilateral cortex was detected by terminal deoxynucleotidyl transferase mediated d-UTP nick end labeling staining (TUNEL). CA1 neuronal loss was counted 24 h after HI by light microscopy. RESULTS: After HI mu-calpain mRNA began to increase at 6 h and reached peak at 24 h compared to the control (1.805 and 4.83 vs. 1, P < 0.05); mu-calpain was activated through autolysis, the ratio of its activated fragment (76 000) vs. whole fragment (80 000) was significantly higher at 6 h (0.547 +/- 0.095) compared to the control (0.095 +/- 0.016, P < 0.05), it reached peak at 24 h (0.921 +/- 0.058, P < 0.01) and was still at a high level at 72 h (0.708 +/- 0.025, P < 0.05). Expression of activated caspase-3 protein reached peak at 24 h (3.78 +/- 0.30, P < 0.01), decreased to the same level as the control (1.56 +/- 0.07) at 72 h (1.82 +/- 0.11, P > 0.05). Apoptotic cells in the cortex ipsilateral to HI insult increased after HIBD, reached peak at 24 h (135.46 +/- 17.52/visual field) and was still markedly higher at 72 h (79.32 +/- 17.79/visual field) compared with the control (5.33 +/- 1.53/visual field, P < 0.01). At 24 h after HI CA1 neuronal loss (30.0 +/- 6.2/oil immersion lens field) in the HIBD group was significantly higher than that of the control (2.4 +/- 0.3/oil immersion lens field, P < 0.01). However, in the MDL group the expressions of mu-calpain and caspase-3 proteins were diminished, TUNEL positive cells at 6 h and 24 h were decreased and CA1 neuronal loss (18.2 +/- 2.4/oil immersion lens field, P < 0.05) was alleviated. The amount of micro-calpain mRNA was decreased in the MDL group, but there was no significant difference compared with the HIBD group. CONCLUSION: mu-calpain gene and protein expressions increased after HI, which may contribute to the pathogenensis of HIBD. Calpain inhibitor-3 may intervene neural necrosis and apoptosis by diminishing expressions of mu-calpain and caspase-3 to play a protective role after HI insult of neonatal brain.

Currently evaluated calpain and caspase inhibitors for neuroprotection in experimental brain ischemia.

Currently available therapies for brain ischemia, with a few exceptions, provide only symptomatic relief in patients. Recent investigations in experimental models provided an understanding of the cellular and molecular mechanisms that lead to neurodegeneration in ischemic injury, and also indicate targets for prevention and amelioration of the devastating consequences of stroke. An enormous increase in intracellular free Ca(2+) levels following stroke activates Ca(2+)-dependent enzymes, contributing to neuronal death and dysfunction. Additionally, ischemic injury generates highly reactive free radicals and triggers release of cytotoxic cytokines for activation of cysteine proteases. A number of studies already indicated a prominent role for the cysteine proteases of the calpain and caspase families in the pathogenesis of brain ischemia. Proteolytic activities of these proteases degrade various cytoskeletal proteins and membrane proteins, destabilizing the structural integrity and forcing the neurons to delayed death in ischemic penumbra. Some current studies have unequivocally confirmed the neuronal apoptosis in ischemia and showed that administration of calpain and caspase inhibitors alone or in combination can provide functional neuroprotection in various animal models of cerebral ischemia. This article will discuss the molecular structures and activities of calpain and caspase inhibitors and their therapeutic efficacy in experimental brain ischemia. However, further investigations are necessary for improvements in the structural design of calpain and caspase inhibitors for their persistent therapeutic efficacy in animal models of stroke and for clinical trials in the future.

Dual inhibition of protein phosphatase-1/2A and calpain rescues nerve growth factor-differentiated PC12 cells from oxygen-glucose deprivation-induced cell death.

In the present study, we examined how the cell survival signaling via cyclic AMP-responsive element binding protein (CREB) and Akt, and the cell death signaling via cystein proteases, calpain and caspase-3, are involved in oxygen-glucose deprivation (OGD) followed by reoxygenation (OGD/reoxygenation)-induced cell death in nerve growth factor (NGF)-differentiated PC12 cells. OGD/reoxygenation-induced cell death was evaluated by LDH release into the culture medium. The level of LDH release was low (9.0% +/- 4.1%) immediately after 4 hr of OGD (0 hr of reoxygenation), was significantly increased to 28.6% +/- 6.6% at 3 hr of reoxygenation, and remained at similar levels at 6 and 20 hr of reoxygenation, suggesting that reoxygenation at least for 3 hr resulted in the loss of cell membrane integrity. After 4 hr of OGD followed by 3 hr of reoxygenation, dephosphorylation of phosphorylated CREB (pCREB), but not phosphorylated Akt (pAkt), was induced. Under these conditions, calpain- but not caspase-3-mediated alpha-spectrin breakdown product was increased, indicating that OGD/reoxygenation also induced an increase in calpain activity. The restoration of pCREB by protein phosphatase (PP)-1/2A inhibitors or the inhibition of excessive activation of calpain by calpain inhibitor did not reduce OGD/reoxygenation-induced LDH release. Cotreatment with PP-1/2A and calpain inhibitors reduced OGD/reoxygenation-induced LDH release. The present study suggests that a balance in the phosphorylation and proteolytic signaling is involved in the survival of NGF-differentiated PC12 cells.

Safety and efficacy of AAV-mediated calpain 3 gene transfer in a mouse model of limb-girdle muscular dystrophy type 2A.

Calpainopathy (limb-girdle muscular dystrophy type 2A, LGMD2A) is a recessive muscular disorder caused by deficiency in the calcium-dependent cysteine protease calpain 3. To date, no treatment exists for this disease. We evaluated the potential of recombinant adeno-associated virus (rAAV) vectors for gene therapy in a murine model for LGMD2A. To drive the expression of calpain 3, we used rAAV2/1 pseudotyped vectors and muscle-specific promoters to avoid calpain 3 cell toxicity. We report efficient and stable transgene expression in muscle with restoration of the proteolytic activity and without evident toxicity. In addition, calpain 3 was correctly targeted to the sarcomere. Moreover, its presence resulted in improvement of the histological features and in therapeutic efficacy at the physiological levels, including correction of atrophy and full rescue of the contractile force deficits. Our results establish the feasibility of AAV-mediated calpain 3 gene transfer as a therapeutic approach.

Chemonucleolysis with calpain I in rabbits.

Calpain I is a calcium-dependent cysteine proteinase that has been recently shown to degrade proteoglycan in vitro. The authors injected calpain I, which was purified from human red blood cells, into the intervertebral discs of rabbits. Roentgenograms showed disc space narrowing 1 week after the injection. Histologically, proteoglycan of the nucleus pulposus and anulus fibrosus decreased and notochordal cells in the nucleus pulposus almost disappeared. Biochemical data of the nucleus pulposus showed that the amounts of smaller proteoglycans increased 1 and 4 weeks after the injection. Eight weeks after the injection, histologic and biochemical data showed recovery compared with the data 1 week after injection. These findings show that calpain I is as potent an enzyme as chondroitinase ABC and has milder chemonucleolytic action than chymopapain. Regarding its possible clinical application, autogenous calpain I as purified from the patient's own red blood cells may have advantages over chymopapain and chondroitinase ABC in that it will prevent anaphylactic reaction.