Inhibition of N-type calcium channels by phenoxyaniline and sulfonamide analogues.

Building on previous investigations, structural modifications to the neuronal calcium ion channel blocker MONIRO-1 and related compounds were conducted that included replacement of the amide linker with an aniline and isosteric sulfonamide moiety, and the previously used strategy of substitution of the guanidinium group with less hydrophilic amine functionalities. A comprehensive SAR study revealed a number of phenoxyaniline and sulfonamide compounds that were more potent or had similar potency for the CaV2.2 and CaV3.2 channel compared to MONIRO-1 when evaluated in a FLIPR-based intracellular calcium response assay. Cytotoxicity investigations indicated that the sulfonamide analogues were well tolerated by Cos-7 cells at dosages required to inhibit both calcium ion channels. The sulfonamide derivatives were the most promising CaV2.2 inhibitors developed by us to date due, possessing high stability in plasma, low toxicity (estimated therapeutic index > 10), favourable CNS MPO scores (4.0-4.4) and high potency and selectivity, thereby, making this class of compounds suitable candidates for future in vivo studies.

Structure-function and rational design of a spider toxin Ssp1a at human voltage-gated sodium channel subtypes.

The structure-function and optimization studies of NaV-inhibiting spider toxins have focused on developing selective inhibitors for peripheral pain-sensing NaV1.7. With several NaV subtypes emerging as potential therapeutic targets, structure-function analysis of NaV-inhibiting spider toxins at such subtypes is warranted. Using the recently discovered spider toxin Ssp1a, this study extends the structure-function relationships of NaV-inhibiting spider toxins beyond NaV1.7 to include the epilepsy target NaV1.2 and the pain target NaV1.3. Based on these results and docking studies, we designed analogues for improved potency and/or subtype-selectivity, with S7R-E18K-rSsp1a and N14D-P27R-rSsp1a identified as promising leads. S7R-E18K-rSsp1a increased the rSsp1a potency at these three NaV subtypes, especially at NaV1.3 (∼10-fold), while N14D-P27R-rSsp1a enhanced NaV1.2/1.7 selectivity over NaV1.3. This study highlights the challenge of developing subtype-selective spider toxin inhibitors across multiple NaV subtypes that might offer a more effective therapeutic approach. The findings of this study provide a basis for further rational design of Ssp1a and related NaSpTx1 homologs targeting NaV1.2, NaV1.3 and/or NaV1.7 as research tools and therapeutic leads.

Voltage-Gated Sodium Channel Modulation by a New Spider Toxin Ssp1a Isolated From an Australian Theraphosid.

Given the important role of voltage-gated sodium (NaV) channel-modulating spider toxins in elucidating the function, pharmacology, and mechanism of action of therapeutically relevant NaV channels, we screened the venom from Australian theraphosid species against the human pain target hNaV1.7. Using assay-guided fractionation, we isolated a 33-residue inhibitor cystine knot (ICK) peptide (Ssp1a) belonging to the NaSpTx1 family. Recombinant Ssp1a (rSsp1a) inhibited neuronal hNaV subtypes with a rank order of potency hNaV1.7 > 1.6 > 1.2 > 1.3 > 1.1. rSsp1a inhibited hNaV1.7, hNaV1.2 and hNaV1.3 without significantly altering the voltage-dependence of activation, inactivation, or delay in recovery from inactivation. However, rSsp1a demonstrated voltage-dependent inhibition at hNaV1.7 and rSsp1a-bound hNaV1.7 opened at extreme depolarizations, suggesting rSsp1a likely interacted with voltage-sensing domain II (VSD II) of hNaV1.7 to trap the channel in its resting state. Nuclear magnetic resonance spectroscopy revealed key structural features of Ssp1a, including an amphipathic surface with hydrophobic and charged patches shown by docking studies to comprise the interacting surface. This study provides the basis for future structure-function studies to guide the development of subtype selective inhibitors.

Spider Knottin Pharmacology at Voltage-Gated Sodium Channels and Their Potential to Modulate Pain Pathways.

Voltage-gated sodium channels (NaVs) are a key determinant of neuronal signalling. Neurotoxins from diverse taxa that selectively activate or inhibit NaV channels have helped unravel the role of NaV channels in diseases, including chronic pain. Spider venoms contain the most diverse array of inhibitor cystine knot (ICK) toxins (knottins). This review provides an overview on how spider knottins modulate NaV channels and describes the structural features and molecular determinants that influence their affinity and subtype selectivity. Genetic and functional evidence support a major involvement of NaV subtypes in various chronic pain conditions. The exquisite inhibitory properties of spider knottins over key NaV subtypes make them the best lead molecules for the development of novel analgesics to treat chronic pain.

Antimicrobial Sensitivity Trend in Blood Culture Positive Enteric Fever.

BACKGROUND: For diagnosis of enteric fever, the culture of the organism from different body fluids is the gold standard. After diagnosis, it is important to treat with the right antibiotic before any complications can occur. The retrospective study is designed to explore the antibiotic sensitivity trend in blood culture positive typhoid fever cases and the extent of drug resistance before treatment is administered. METHODS: A retrospective study was carried out for culture isolated enteric fever patients admitted in Kathmandu Model Hospital. The discharged records from January 2012 to December 2016 were analyzed. The patients above 15 years and with culture isolated enteric fever were included in the study. RESULTS: One hundred fifty-nine strains of Salmonella typhi and paratyphi were isolated from Jan 2012 to Dec 2016 at Kathmandu Model Hospital. Out of 159 isolated, 125 (78.6%) were Salmonella typhi and 34 (21.4%) were paratyphi. Among them co-trimoxazole, chloramphenicol, ceftriaxone, cefotaxime, cefixime, and ofloxacin demonstrated 100% sensitivity. Similarly, amoxicillin sensitivity was 98.1% (n=156) while ciprofloxacin was sensitive in 6.3% (n=10), intermediately sensitive in 49.1% (n=78) and resistance in 44.7% (n=71).The newer quinolone levofloxacin showed 78.5% (n=11) sensitivity. Azithromycin was sensitive in 99.2% (n=132) of total isolated Salmonella species both typhi and paratyphi. CONCLUSIONS: A high degree of sensitivity was noted to chloramphenicol and co-trimoxazole, showing sensitivity has returned to conventional antibiotics. The drug-like ofloxacin is still the best responding drug in our contest whereas ciprofloxacin resistance is still high, but five years patterns show a trend of rollback of sensitivity.

Transabdominal Pre-peritoneal Mesh Repair versus Lichtenstein's Hernioplasty.

BACKGROUND: In the era of minimal invasive surgery, hernia repair has seen a paradigm shift from open to laparoscopic technique. However, superiority of laparoscopic repair over open repair is still controversial. Available literatures have shown laparoscopic technique to be better in term of post-operative pain and early return to work. METHODS: In this prospective study, a total of 102 patients aged 21-78 years with inguinal hernia were recruited and enrolled into two comparative groups, namely Lichtenstein's and Transabdominal pre-peritoneal, and each group containing 51 participants. Hospital ethical committee approval and written informed consent from patients was obtained. Primarily, the duration of operation, post-operative pain and complication, and quality of life after surgery was compared between the two different approaches of hernia repair. RESULTS: The study results demonstrated a statistically significant superiority of trans abdominal pre-peritoneal repair over Lichtenstein's hernioplasty in terms of post operative pain (2.00±0.63 vs 3.90±0.74 VAS score, P value<0.001), hospital stay (2.33±0.62 vs 2.96±0.20 days, P value <0.001) and quality of life with early return to normal work (13.39±0.60 vs 17.88±0.86 days, P value <0.001); whereas a prolonged operative time was seen in transabdominal pre-peritoneal repair (96.08±27.08 vs 42.55±5.95 mins, P value <0.001). CONCLUSIONS: This study has shown that transabdominal pre-peritoneal repair is better than Lichtenstein's in respect to post-operative pain, quality of life and post-operative complication. However, it has prolonged operative duration than conventional method.

The standard aqueous stem bark extract of Mangifera indica L. inhibits toxic PLA2 - NN-XIb-PLA2 of Indian cobra venom.

The aqueous extract of Mangifera indica is known to possess diverse medicinal properties, which also includes anti-snake venom activities. However, its inhibitory potency and mechanism of action on multi-toxic snake venom phospholipases A2s are still unknown. Therefore, the objective of this study was to evaluate the modulatory effect of standard aqueous bark extract of M. indica on NN-XIb-PLA2 of Indian cobra venom. The in vitro sPLA2, in situ hemolytic and in vivo edema inhibition effect were carried out as described. Also the effect of substrate and calcium concentration was carried out. M. indica extract dose dependently inhibited the GIA sPLA2 (NN-XIb-PLA2) activity with an IC50 value of 7.6 µg/ml. M. indica extract effectively inhibited the indirect hemolytic activity up to 98% at ∼40 µg/ml concentration. Further, M. indica extract (0-50 µg/ml) inhibited the edema formed in a dose dependent manner. When examined as a function of increased substrate and calcium concentration, there was no relieve of inhibitory effect of M. indica extract on the NN-XIb-PLA2. Further, the inhibition was irreversible as evident from binding studies. The in vitro inhibition is well correlated with in situ and in vivo edema inhibiting activities of M. indica. As the inhibition is independent of substrate and calcium and was irreversible, it can be concluded that M. indica extract mode of inhibition could be due to direct interaction of components present in the extract with the PLA2 enzyme. The aqueous extract of M. indica effectively inhibits svPLA2 enzymatic and its associated toxic activities, which substantiate their anti-snake venom properties. Further in-depth studies on the role and mechanism of the principal constituents present in the extract, responsible for the anti-PLA2 activity will be interesting to develop them into potent antisnake component and also as an anti-inflammatory agent.

Wasp Venom Toxins as a Potential Therapeutic Agent.

It is high time now to discover novel drugs due to the increasing rate of drug resistance by the pathogen organisms and target cells as well as the dependence or tolerance of the body towards the drug. As it is obvious that significant numbers of the modern day pharmaceuticals are derived from natural products, it is equally astonishing to accept that venoms of various origins have therapeutic potentials. Wasp venoms are also a rich source of therapeutically important toxins which includes short cationic peptides, kinins, polyamines and polyDNA viruses, to name a few indentified. Wasp venom cationic peptides, namely mastoparan and its analogs, show a very important potency as an antimicrobial and anticancer agents of the future. They have proven to be the better candidates due to their lesser toxic effects and higher selectivity upon chemical modification and charge optimization. They also have superiority over the conventional chemical drugs as the target cells very rarely develop resistance against them because these peptides primarily imparts its effect through biophysical interaction with the target cell membrane which is dependent upon the net charge of the peptide, its hydrophobicity and anionicity and fluidity of the target cell membranes. Besides, the other components of wasp venom such as kinins, polyamines and polyDNA viruses show various pharmacological promise in the treatment of pain, inflammatory disease, and neurodegenerative diseases such as epilepsy and aversion.

Prophylactic administration of ondansetron in prevention of intrathecal morphine-induced pruritus and post-operative nausea and vomiting in patients undergoing caesarean section.

BACKGROUND: Intrathecal morphine is commonly used for post caesarean analgesia. However, their use is frequently associated with the incidence of troublesome side effects such as nausea, vomiting and pruritus. Various mechanisms have been postulated for the opioid-induced pruritus, with a variety of medications with different mechanisms of actions formulated for the prevention and treatment. But, the results are inconsistent and hence the prevention and treatment of opioid-induced pruritus still remains a challenge. Ondansetron which is antiemetic, non-sedative and has no antianalgesic effect is an antagonist to 5-HT3 receptor, the receptor with which opioids interacts and imparts its effects. Ondansetron, thus, would be an attractive treatment strategy for both opioid-induced pruritus and post-operative nausea and vomiting. METHODS: After the approval from institutional review committee and written consent received from the patient, 50 healthy parturients of ASA I and II physical status undergoing caesarean section under spinal anaesthesia were enrolled for the study. They were randomly categorized into placebo group (2 ml normal saline) and treatment group (2 ml of 4 mg ondansetron), each group containing 25 patients. Pruritus and post-operative nausea and vomiting scores were recorded up to 24 hours after the administration of intrathecal morphine. Statistical analysis was performed using chi-square test. RESULTS: The incidence, severity and necessity of treatment for pruritus in the treatment group was significantly reduced compared to the placebo group (16% vs 88%). Similarly, the risk of post-operative nausea and vomiting in the treatment group was less compared to the placebo group (8% vs 56%). CONCLUSION: Prophylactic administration of ondansetron to parturients receiving intrathecal morphine for post-operative analgesia provides a significant reduction of intrathecal morphine-induced pruritus and nausea and vomiting. TRIAL REGISTRATION: CTRI/2015/01/005362 registered on 07/01/2015 in Clinical Trials Registry-India (ctri.nic.in).

Acute renal failure following multiple hornet stings.

Hornet stings are medically important stings which can cause allergic manifestations and, in severe cases, may lead to the unusual complication of acute renal failure (ARF) and other systemic complications. ARF results from toxic or ischaemic acute tubular necrosis in a setting of haemolysis or rhabdomyolysis or both and acute allergic interstitial nephritis. Venom from hornet stings can also contribute to myocardial injury or liver impairment. Here, we report three cases of hornet stings leading to ARF. Case #1 and Case #3 recovered their renal function and body physiology after a 38-day and 15-day stay in the hospital, respectively, whereas Case #2 died. They were meticulously supported by haemodialysis along with the combination of various drug regimens.