MDL 28170

MDL 28170 is a selective inhibitor, which inhibites calpain with Ki values of 10nM and cathepsin B with Ki values of 25 nM while does not inhibit trypsin-like serine proteases. And it can penetrate the blood–brain barrier rapidly and show the activity in inhibiting brain cysteine protease activity following systemic administration [1,2].

Calpain could affect reperfusion function directly through limited proteolysis of the sarcomeres.And function improvement of MDL-28170 during reperfusion were supported byexperimets. It is thought to act by blocking the sites of catalysis ofcalpains. The experiments also showed skinned muscle fibers which was isolated from the tropical of stunned ferret hearts reveal decreased sensitivity to Ca2+, and the decrease in sensitivity could be reversed if MDL-28170 is treated prior to ischemia and during early reperfusion [1].

When peritoneal mouse macrophages were pre-infected with trypomastigotes for 3 h , MDL28170 was able to reduce the viability of bloodstream trypomastigotes significantly with an IC50/24h value of 20.4 mM. Also, asparasitespre-treated with MDL28170 concentration rose from 6.25 to 50 mM, presenting a clear dose-dependent inhibition profile prior to of macrophage, where the corresponding inhibition from 20% increased to 50%. In addition, macrophages experimentally infected with T. cruzi which were treated with MDL 28170 presented a reduction in the percentage of infection even at the lowest concentrations of 6.25 mM [3].

Upon Ca2+ repletion in the isolated heart of rats, the hearts deteriorated immediately, revealing a marked depression in cardiac function and an enlarged myocardial injury area. This was accompanied by significant increases in lactate dehydrogenase, mitochondrial release of cytochrome c, the apoptotic index and degraded TnI. MDL 28170 significantly inhibited these changes, with the exception of TnI degradation [4].

References:
[1].  Urthaler F, Wolkowicz PE, Digerness SB, et al. MDL-28170, a membrane-permeantcalpain inhibitor, attenuates stunning and PKC epsilon proteolysis in reperfused ferret hearts. Cardiovasc Res, 1997, 35 (1): 60-7.
[2].  Li P, Wendy H, He Q, et al. Postischemic treatment withcalpain inhibitor MDL 28170ameliorates brain damage in a gerbil model of global ischemia, Neuroscience Letters, 1998, 247 :17–20.
[3].  V?′tor EV, Rubem F, Andre′ L, Effects of the calpain inhibitor MDL28170 on the clinically relevant forms of Trypanosomacruzi in vitro. J AntimicrobChemother , 2010, 65: 1395–1398.
[4].  Bi S H, Jin Z X, Zhang J Y, et al. Calpaininhibi tor MDL 28170 protectsagainst the Ca2+paradox in rat hearts.Clinical and Experimental Pharmacology and Physiology , 2012, 39:385–392 .

A pharmacological analysis of the neuroprotective efficacy of the brain- and cell-permeable calpain inhibitor MDL-28170 in the mouse controlled cortical impact traumatic brain injury model.[Pubmed:20874056]

J Neurotrauma. 2010 Dec;27(12):2233-43.

The cytoskeletal and neuronal protective effects of early treatment with the blood-brain barrier- and cell-permeable calpain inhibitor MDL-28170 was examined in the controlled cortical impact (CCI) traumatic brain injury (TBI) model in male CF-1 mice. This was preceded by a dose-response and pharmacodynamic evaluation of IV or IP doses of MDL-28170 with regard to ex vivo inhibition of calpain 2 activity in harvested brain homogenates. From these data, we tested the effects of an optimized MDL-28170 dosing regimen on calpain-mediated degradation of the neuronal cytoskeletal protein alpha-spectrin in cortical or hippocampal tissue of mice 24 h after CCI-TBI (1.0 mm depth, 3.5 m/sec velocity). With treatment initiated at 15 min post-TBI, alpha-spectrin degradation was significantly reduced by 40% in hippocampus and 44% in cortex. This effect was still observed with a 1-h but not a 3-h post-TBI delay. The cytoskeletal protection is most likely taking place in neurons surrounding the area of mainly necrotic degeneration, since MDL-28170 did not reduce hemispheric lesion volume as measured by the aminocupric silver staining method. This lack of effect on lesion volume has been seen with other calpain inhibitors, which suggests that pharmacological calpain inhibition by itself, while able to reduce axonal injury, may not be able to produce a measurable reduction in lesion volume. This is in contrast to certain other neuroprotective mechanistic approaches such as the mitochondrial protectant cyclosporine A, which produces at least a partial decrease in lesion volume in the same model. Accordingly, the combination of a calpain inhibitor with a compound such as cyclosporine A may be needed to achieve the optimal degree of post-TBI neuroprotection.

Calpain inhibitor, MDL 28170 confer electrophysiological, nociceptive and biochemical improvement in diabetic neuropathy.[Pubmed:26087461]

Neuropharmacology. 2015 Oct;97:113-21.

Calpain plays an important role in the pathophysiology of neurological and cardiovascular complications, but its functional association in diabetic neuropathy is not yet elucidated. Therefore, we investigated the role of calpain in modulation of tetrodotoxin-resistant sodium channels (TTX-R Na(+) channels) in dorsal root ganglion (DRG) neurons using a pharmacological approach. The effects of a calpain inhibitor, MDL 28170 (3 and 10 mg/kg, i.p.) on TTX-R Na(+) channels in DRG neurons of streptozotocin-induced diabetic rats were assessed by using whole-cell patch-clamp technique. In addition to this biochemical, functional and behavioral deficits were also measured. Diabetic rats demonstrated the mechanical allodynia and thermal hyperalgesia with reduced nerve perfusion and conduction velocity as compared to control. MDL 28170 treatments significantly recovered these functional and nociceptive deficits. Moreover, diabetic rats exhibited increased calpain activation, lipid peroxidation and proinflammatory cytokines as compared to control. Drug treatment significantly improved these biochemical deficits. Additionally, DRG neurons from diabetic rats illustrated a significant increase in TTX-R sodium current (INa) density as compared to control. MDL 28170 treatments in diabetic rats significantly blocked the altered channel kinetics with hyperpolarizing shift in voltage-dependence of steady-state activation and inactivation curves. All together, our study provides evidence that calpain activation is directly associated with alterations in TTX-R Na(+) channels and triggers functional, nociceptive and biochemical deficits in experimental diabetic neuropathy. The calpain inhibitor, MDL 28710 have shown beneficial effects in alleviating diabetic neuropathy via modulation of TTX-R Na(+) channel kinetics and reduction of oxidative stress and neuro-inflammation.

Calpain inhibitor MDL 28170 protects against the Ca2+ paradox in rat hearts.[Pubmed:22356295]

Clin Exp Pharmacol Physiol. 2012 Apr;39(4):385-92.

The calcium paradox represents an important model in which to study myocardial injuries due to intracellular Ca(2+) overload. In a previous study, calpain was transiently activated in Ca(2+) -paradoxic hearts. The aim of the present study was to determine the role of calpain in myocardial dysfunction in hearts subjected to the Ca(2+) paradox and to elucidate the underlying mechanisms. Rat hearts were isolated, Langendorff perfused and subjected to the Ca(2+) paradox, which was induced by 3 min Ca(2+) depletion followed by 30 min Ca(2+) repletion, in the presence or absence of the calpain inhibitor 10 umol/L MDL 28170. Cardiac function was evaluated. Furthermore, cell death and the degradation of troponin I (TnI) were assessed and calpain activity was determined by measurement of the alpha-fodrin fragment and confocal image analysis. Upon Ca(2+) repletion, the hearts immediately deteriorated, exhibiting a marked depression in cardiac function and an enlarged myocardial injury area. This was accompanied by significant increases in lactate dehydrogenase, mitochondrial release of cytochrome c, the apoptotic index and degraded TnI. These changes were significantly inhibited by MDL 28170, with the exception of TnI degradation. Compared with the control group, Ca(2+) -paradoxic hearts showed a marked increase in cleaved 150 kDa fragments resulting from specific calpain-mediated proteolysis of alpha-fodrin. This effect was attenuated by MDL 28170. Confocal image analysis revealed the translocation of both mu- and m-calpain to the sarcolemmal membrane in Ca(2+) -paradoxic hearts, indicating increased activity of both isoforms. The results suggest that the Ca(2+) paradox promotes calpain activity, leading to necrosis, apoptosis and myocardial dysfunction.

Short-duration treatment with the calpain inhibitor MDL-28170 does not protect axonal transport in an in vivo model of traumatic axonal injury.[Pubmed:22077394]

J Neurotrauma. 2012 Jan 20;29(2):445-51.

Traumatic axonal injury is characterized by early cytoskeletal proteolysis and disruption of axonal transport. Calpain inhibition has been shown to protect axons in rodent models of traumatic brain injury. However, in these models, both white and gray matter are injured, making it difficult to determine if calpain inhibitors are directly protecting injured axons. To address this issue, we used our rat optic nerve stretch model to test the hypothesis that early calpain inhibition directly protects central nervous system (CNS) axons following stretch injury. Rats were given an intravenous bolus of the calpain inhibitor MDL-28170 (30 mg/kg) 30 min prior to unilateral optic nerve stretch, followed by a 15 mg/kg/h intravenous infusion over the next 2.5 h. Immunohistochemical analysis of optic nerves 30 min after stretch injury revealed variable increases of calpain-cleaved alpha-spectrin that appeared less evident in stretched nerves from drug-treated rats, although this difference was not statistically significant. Retrograde axonal transport measured by Fluorogold(R) labeling of retinal ganglion cells was significantly impaired after stretch injury. However, there was no difference in the number of Fluorogold-labeled cells in the vehicle vs. drug treatment groups. These results suggest that early short-duration calpain inhibitor therapy with MDL-28170 is not an effective strategy to prevent disruption of axonal transport following isolated axonal stretch injury in the CNS.

Calpain inhibitor MDL-28170 reduces the functional and structural deterioration of corpus callosum following fluid percussion injury.[Pubmed:17600513]

J Neurotrauma. 2007 Jun;24(6):960-78.

It is known that calpain activation is involved in human traumatic brain injury (TBI) and that calpain inhibition can have neuroprotective effects on both gray matter and white matter injury of TBI models. However, the role of calpain activation in the corpus callosum remains unclear and requires elucidation given its potential clinical relevance. We evaluated the neuroprotective effects of calpain inhibitor MDL-28170 on corpus callosum function and structural destruction using a fluid percussion injury (FPI) model. The therapeutic time window for a single administration of MDL-28170 was up to 4 h post injury in protecting the corpus callosum structural integrity, and up to 30 min in protecting the axonal function evaluated 1 day following injury. When given 30 min prior injury, MDL-28170 showed neuroprotective effects that lasted up to 7 days. However, 30 min post injury administration of the drug afforded neuroprotection only up to 3 days. In contrast, two additional reinforcement injections at 24 and 48 h in addition to 30 min post FPI significantly protected both axonal function and structural integrity that lasted 14 days following FPI. Our data indicated that calpain inhibitor MDL-28170 is an effective neuroprotectant for axonal injury in corpus callosum following FPI with a therapeutic time window up to 4 hours. Although delayed treatment (2 or 4 h post FPI) was effective in protecting the axonal structure, the axons saved may not be as functional as normal fibers. Multiple drug administrations may be necessary for achieving a persisting effectiveness of this compound.

Postischemic treatment with calpain inhibitor MDL 28170 ameliorates brain damage in a gerbil model of global ischemia.[Pubmed:9637399]

Neurosci Lett. 1998 May 8;247(1):17-20.

The newly-developed calpain inhibitor, MDL 28170 penetrates the blood-brain barrier and inhibits brain cysteine protease activity after systemic administration. This experiment was initiated to determine if the calpain inhibitor, MDL 28170 could, by these actions, reduce neuronal damage in an animal model of global cerebral ischemia in the gerbil. The calpain inhibitor, MDL 28170 (50 mg/kg), was initiated at 0.5 and 3 h of recirculation following 5min of global ischemia. Animals subjected to ischemia but without treatment or with vehicle treatment served as controls. Evaluation by light microscopy was carried out on paraffin-embedded brain sections of gerbils which were sacrificed 7 days post-operatively. The results show that the calpain inhibitor, MDL 28170, protects against cortical neuronal damage even if the treatment is delayed until 3 h after reperfusion. However, the neuroprotective effect of this agent is less pronounced in the hippocampal CA1 sector. The results suggest that calpain-mediated proteolysis plays an important role in neuronal death due to ischemia. However, additional mechanisms by which an increased intracellular calcium concentration leads to neuronal death may exist.

Neuronal recovery after moderate hypoxia is improved by the calpain inhibitor MDL28170.[Pubmed:9374290]

Brain Res. 1997 Sep 19;769(1):188-92.

The role of calcium-activated proteolysis in hypoxic neuronal injury was investigated using an in vitro slice model of moderate hypoxia that mimics many features of an ischemic penumbra. The calpain inhibitor, MDL28170, significantly improved the recovery of synaptic responses in hippocampal slices following prolonged, moderate hypoxia without hypoxic depolarization. This finding further implicates calpain-mediated proteolysis in the development of neuronal injury following moderate metabolic challenge such as occurs in regions of partial ischemia.

Cell-penetrating inhibitors of calpain.[Pubmed:1877091]

Trends Biochem Sci. 1991 Apr;16(4):150-3.

Inhibitors of the calcium-dependent cysteine protease calpain are described that are new analogs of the naturally-occurring compounds E-64 and leupeptin. These new derivatives, unlike the parent compounds, can inhibit calpain within cells. Their lack of charged groups probably accounts for this improved membrane permeability. These new inhibitors are proving useful in exploration of the role of calpain in many cellular processes, including platelet activation.

MDL-28170 (Calpain Inhibitor III) is a potent, selective and membrane-permeable cysteine protease inhibitor of calpain that rapidly penetrates the blood-brain barrier following systemic administration. MDL-28170 also block γ-secretase.

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