Prinomastat

Venoms are evolutionary novelties that have real-world implications due to their impact upon human health. However, relative to the abundant studies of elapid and viperid snake venoms, fewer investigations have been undertaken on those of rear-fanged snakes as they are more problematic for obtaining venom. While most rear-fanged venomous snakes are not considered to be of great medical importance, several species are capable of producing fatalities. Most notable among these are snakes from the genus Rhabdophis, the Asian "keelback" snakes. Prior work have described potent procoagulant toxicity suggesting Factor X and prothrombin activation, but did not investigate the ability to activate other clotting factors. Here we show that in addition to activating both Factor X and prothrombin (with prothrombin twice that of FX), the venom of Rhabdophis subminiatus is able to more potently activate Factor VII (ten times that of prothrombin), while also activating FXII and FIX equipotently to prothrombin, and with FXI also activated but at a much lower level. The ability to activate FVII represents a third convergent evolution of this trait. The Australian elapid clade of [Oxyuranus (taipans) + Pseudonaja (brown snakes)] was the first identified to have evolved this trait. and only recently was it shown to be independently present in another lineage (the Central American viperid species Porthidium volcanicum). In addition, the abilities to activate FXI and FXII are also convergent between R. subminiatus and P. volcanicum, but with R. subminiatus being much more potent. By testing across amphibian, avian, and mammalian plasmas we demonstrate that the venom is potently procoagulant across diverse plasma types. However, consistent with dietary preference, R. subminiatus venom was most potent upon amphibian plasma. While a Rhabdophis antivenom is produced in Japan to treat R. tigrinus envenomings, it is scarce even within Japan and is not exported. As this genus is very wide-ranging in Asia, alternate treatment options are in need of development. Hence we tested the ability of candidate, broad-spectrum enzyme inhibitors to neutralize R. subminiatus venom: marimastat was more effective than prinomastat but both marimastat and prinomastat were significantly more effective than DMPS (2,3-Dimercapto-1-propanesulfonic acid). The findings of this study shed light on the evolution of these fascinating rear-fanged snakes as well as explored their systemic effects upon blood coagulation and point to potential treatment options for the rare, but potentially lethal encounters.

Facial nerve injury results in degradation of the neuromuscular junction (NMJ) and blocks neurotransmission between the pre- and postsynaptic structures, which are separated by a synaptic cleft. Matrix metalloproteinases (MMPs), enzymes that degrade and modify the extracellular matrix, play critical roles in regulating NMJ remodeling. We previously demonstrated that MMP1, MMP2, MMP3, MMP7, and MMP9 are overexpressed in facial nerve-innervated orbicularis oris muscle after facial nerve injury in a rat model. In the present study, the MMP inhibitor prinomastat was administered to rats after facial nerve injury. The MMP levels, agrin expression, and muscle-specific kinase (MuSK) phosphorylation were evaluated. Variations in evoked electromyography (EEMG) amplitude were also recorded. Compared with the control group, MMP expression in the orbicularis oris after facial nerve injury was significantly reduced in the prinomastat group. Inhibition of MMP expression maintained agrin expression and MuSK phosphorylation; the NMJ morphology was also protected after the injury. Moreover, prinomastat treatment sustained EEMG amplitude and muscle tension after the injury. These findings indicate that inhibiting MMPs can protect the function and morphology of the NMJ and demonstrate the need for protection of the NMJ at early stages after facial nerve injury.