New fron­tier for med­i­cal cannabis — top­i­cal pot

Anti-in­flam­ma­tory traits helped heal skin of mice in study

San Francisco Chronicle - - Bay Area And California - By Kavita Mishra Chron­i­cle Staff Writer

Skin al­ler­gies may be the next rea­son to use mar­i­juana — a top­i­cal form, at least.

Sci­en­tists have long sus­pected that mar­i­juana, used for recre­ational pur­poses and to help fight chronic pain, nausea and even some men­tal disor­ders like anx­i­ety and de­pres­sion, also had an­ti­in­flam­ma­tory ef­fects in the body. Now they think they know why. In a study pub­lished in the cur­rent is­sue of the jour­nal Science, re­searchers show ex­actly how they think that works, elu­ci­dat­ing how the body’s own cannabi­noids, com­pounds that are sim­i­lar to the ones found in mar­i­juana, re­duce in­flam­ma­tion.

Mice had a harder time heal­ing from wounds caused by ear tags used to iden­tify them when re­searchers blocked their in­ter­nal cannabi­noids, said Dr. Meliha Karsak, lead au­thor and sci­en­tist in molec­u­lar neu­ro­bi­ol­ogy at the Univer­sity of Bonn in Ger­many. Cannabi­noids are in­volved in many of the body’s daily func­tions, sci­en­tists be­lieve, but they’re still try­ing to fig­ure out how.

Mice also healed faster from skin al­ler­gies with top­i­cal THC, the main psy­choac­tive in­gre­di­ent in mar­i­juana and other plants, she said.

Dr. Frank Lu­cido, a Berke­ley physi­cian who was not in­volved in the study but reg­u­larly rec­om­mends med­i­cal mar­i­juana, said the plant’s anti-in­flam­ma­tory ef­fects didn’t sur­prise him. He has had pa­tients who say their pso­ri­a­sis, an im­mune dis­ease that af­fects the skin and joints, and asthma get bet­ter when they smoke mar­i­juana.

In the 1980s, sci­en­tists dis­cov­ered re­cep­tors in the body that re­spond to ac­tive com­pounds in cannabis, Karsak said. Once ac­ti­vated with THC and other chem­i­cals from mar­i­juana, the re­cep­tors had ef­fects down­stream, for in­stance chang­ing a per­son’s mood and per­cep­tion. Since then, two main re­cep­tors have been stud­ied: One is more preva­lent in the cen­tral ner­vous sys­tem, the other in the pe­riph­ery.

The one in the pe­riph­ery seems to re­spond to cannabi­noids in in­flam­ma­tion and is found in cells of the im­mune sys­tem, said Dr. Don­ald Abrams, a San Fran­cisco Gen­eral Hospi­tal physi­cian who has stud­ied the ef­fects of mar­i­juana use in HIV pa­tients.

“Most peo­ple have be­lieved for some time that the cannabi­noid sys­tem is in­volved in mod­u­lat­ing the im­mune sys­tem,” he said.

But ex­perts say they’re un­cer­tain how such a con­tro­ver­sial chem­i­cal could reach the hands of pa­tients with skin al­ler­gies. Sci­en­tists would have to de­velop a prod­uct that had more ef­fect on the cannabi­noid re­cep­tors in the pe­riph­ery than in the brain and spinal cord, where the psy­chotropic ef­fects would be more com­mon, said Dr. Ben Cra­vatt, a re­searcher in the study and a pro­fes­sor in cell bi­ol­ogy at the Scripps Re­search In­sti­tute in La Jolla.

Karsak, how­ever, said the ex­per­i­ments on mice showed that the dose of THC in a top­i­cal cream for hu­mans would be small enough to avoid psy­chotropic ef­fects. She also doubted that peo­ple could ex­tract enough THC from the cream for use as a recre­ational drug.

Con­tact with sub­stances like poi­son oak can eas­ily cause a blis­ter­ing, al­ler­gic skin re­ac­tion, said Dr. Stephen Katz, a der­ma­tol­o­gist and head of the Na­tional In­sti­tute of Arthri­tis and Mus­cu­loskele­tal and Skin Dis­eases. Top­i­cal steroids and other med­i­ca­tions work well against der­mati­tis, he said, adding that he didn’t think enough was known about cannabi­noids and skin re­ac­tions to cre­ate a med­i­ca­tion from cannabi­noids.

Dr. Mark Dahl, chair­man of der­ma­tol­ogy at the Mayo Clinic Col­lege of Medicine in Ari­zona, cau­tioned pa­tients against us­ing mar­i­juana for their skin al­ler­gies. “I doubt that if they had a rash, rub­bing their mar­i­juana plant would make much dif­fer­ence,” he said.

Cal­i­for­nia is the only state to al­low physi­cians to rec­om­mend mar­i­juana for any med­i­cal pur­pose, un­like other states that dic­tate its use in spe­cific ail­ments, Lu­cido said.

Seventy-five per­cent of the pa­tients Lu­cido treats with mar­i­juana com­plain of chronic pain. The rest have post-trau­matic stress dis­or­der, de­pres­sion, anx­i­ety, headaches or mus­cle spasms, like in pa­tients with mul­ti­ple scle­ro­sis.

He said he hoped the study would con­vince politi­cians to in­vest in more re­search about cannabi­noids and help get more states to pass med­i­cal mar­i­juana laws. E-mail Kavita Mishra at [email protected]­i­

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